Hi all,
I've identified an issue with my Uher tape recorder and I'd like your opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy'
...What,
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your
opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Make a probe to feed the signal into on a high-impedance, high-gain
amplifier and trace the signal through the machine. Is it diistorted at
the playback head? At the volume control? At the line-level output?
At the loudspeaker terminals (you could have a damaged loudspeaker)?
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your
opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through the
amp chain.
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Make a probe to feed the signal into on a high-impedance, high-gain >amplifier and trace the signal through the machine. Is it diistorted at >the playback head? At the volume control? At the line-level output?
At the loudspeaker terminals (you could have a damaged loudspeaker)?
A scope would function in such a role just the same AFAICS., would it
not?
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your
opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through the
amp chain.
I can't follow your logic. If the tape sounds good in some places and >distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not the >amplifier.
Turn down the volume and listen carefully to the tape transport - is it >squealing during the distorted passages? Does the tape each side of the
head block appear to be running normally or is it shuddering because of >patches of sticky-shed? Rest your finger gently on the feed spool and
feel for any vibration, then try gently putting a bit of load on it
until the tape slows down a fraction. If it is unduly sensitive to the
load test or stops dead with little pressure, there is some sticky gunge >lurking somewhere you haven't looked yet.
[...]
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Make a probe to feed the signal into on a high-impedance, high-gain
amplifier and trace the signal through the machine. Is it diistorted at
the playback head? At the volume control? At the line-level output?
At the loudspeaker terminals (you could have a damaged loudspeaker)?
A scope would function in such a role just the same AFAICS., would it
not?
Depending on the type of distortion, it might be quite difficult to see
on a 'scope but very obvious to hear through an amplifier. On a 'scope, >distortion of 10% on a sinewave will show up if you know what you are
looking for - but on complex programme material even 30% may not be >detectable on a 'scope trace. On a listening test, as little as 2% is >detectable on sinewaves and 'clean' programme material - but with
material that has been distorted for 'musical' effect, all bets are off.
On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your >> >> opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently >> >> varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through the
amp chain.
I can't follow your logic. If the tape sounds good in some places and >distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not the >amplifier.
Makes no sense to me, that observation. The tape is brand new and from
a well-respected manufacturer. Think about it, the signal on the tape
didn't get 'impressed' there direct from a microphone or whatever, it
had to be amplified. It had to pass through the amplifier chain and be
mixed with the output from the bias oscillator, so whatever defects
were present at that moment from moment to moment from the amp as the
tape passed, will be faithfully recorded and re-playable.
I assume we're not on the same page, so will not address your
follow-up until we're straight on this one.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your >> >> >> opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape >> >> >> etc etc. So when I'm listening to playback, the quality is frequently >> >> >> varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through the
amp chain.
I can't follow your logic. If the tape sounds good in some places and
distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not the
amplifier.
Makes no sense to me, that observation. The tape is brand new and from
a well-respected manufacturer. Think about it, the signal on the tape
didn't get 'impressed' there direct from a microphone or whatever, it
had to be amplified. It had to pass through the amplifier chain and be
mixed with the output from the bias oscillator, so whatever defects
were present at that moment from moment to moment from the amp as the
tape passed, will be faithfully recorded and re-playable.
I assume we're not on the same page, so will not address your
follow-up until we're straight on this one.
My apologies, I was assuming you were playng back a tape that had been >recorded some time ago and it had recently begun sounding distorted. I >hadn't realised you were looking for the cause of distortion in the >*recording* amplifier.
In that case you need to monitor the signal going to the recording head >(preferably just before the point where the high-frequency bias is
added). If that is clean, suspect there is poor contact between the
head and the tape. The head-tape contact is far more critical on record
than on playback. If the bias is varying, that can cause all sorts of >problems but that is much less likely to be happening. Frequency
modulation of the sound by tape head squeal is another possibility, >especially with new tape that might have a manufacturing defect, or very
old tape that has begun to deteriorate.
Dirty contacts in the record/playback switch can manifest themselves as >variations in signal level and distortion and are more likley to occur
in a machine that hasn't been used for recording for a long period..
....But, the head-tape contact should be your first suspect.
My previous remarks about distortion being much easier to detect by >listening, rather than with an oscilloscope, still apply. If you have a >sinewave signal generator, that will make it much easier to hear
distortion than trying to spot subtle changes by listening to programme >material.
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your >> >> >> opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape >> >> >> etc etc. So when I'm listening to playback, the quality is frequently >> >> >> varying from 'pretty good' to 'really quite crappy'
Does it become good and bad at the same places each time you play the
same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through the
amp chain.
I can't follow your logic. If the tape sounds good in some places and
distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not the
amplifier.
Makes no sense to me, that observation. The tape is brand new and from
a well-respected manufacturer. Think about it, the signal on the tape
didn't get 'impressed' there direct from a microphone or whatever, it
had to be amplified. It had to pass through the amplifier chain and be
mixed with the output from the bias oscillator, so whatever defects
were present at that moment from moment to moment from the amp as the
tape passed, will be faithfully recorded and re-playable.
I assume we're not on the same page, so will not address your
follow-up until we're straight on this one.
My apologies, I was assuming you were playng back a tape that had been >recorded some time ago and it had recently begun sounding distorted. I >hadn't realised you were looking for the cause of distortion in the >*recording* amplifier.
In that case you need to monitor the signal going to the recording head >(preferably just before the point where the high-frequency bias is
added). If that is clean, suspect there is poor contact between the
head and the tape. The head-tape contact is far more critical on record
than on playback. If the bias is varying, that can cause all sorts of >problems but that is much less likely to be happening. Frequency
modulation of the sound by tape head squeal is another possibility, >especially with new tape that might have a manufacturing defect, or very
old tape that has begun to deteriorate.
Dirty contacts in the record/playback switch can manifest themselves as >variations in signal level and distortion and are more likley to occur
in a machine that hasn't been used for recording for a long period..
....But, the head-tape contact should be your first suspect.
My previous remarks about distortion being much easier to detect by >listening, rather than with an oscilloscope, still apply. If you have a >sinewave signal generator, that will make it much easier to hear
distortion than trying to spot subtle changes by listening to programme >material.
On Sat, 10 Jan 2026 22:25:54 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like
your opinion. There's a problem with the audio amplifier chain.
I've eliminated all other possible causes like dirty heads or
faulty tape etc etc. So when I'm listening to playback, the
quality is frequently varying from 'pretty good' to 'really quite
crappy'
Does it become good and bad at the same places each time you play
the same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through
the amp chain.
I can't follow your logic. If the tape sounds good in some places and
distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not
the amplifier.
Makes no sense to me, that observation. The tape is brand new and from
a well-respected manufacturer. Think about it, the signal on the tape
didn't get 'impressed' there direct from a microphone or whatever, it
had to be amplified. It had to pass through the amplifier chain and be
mixed with the output from the bias oscillator, so whatever defects
were present at that moment from moment to moment from the amp as the
tape passed, will be faithfully recorded and re-playable. I assume
we're not on the same page, so will not address your follow-up until
we're straight on this one.
My apologies, I was assuming you were playng back a tape that had been >recorded some time ago and it had recently begun sounding distorted. I >hadn't realised you were looking for the cause of distortion in the >*recording* amplifier.
In that case you need to monitor the signal going to the recording head >(preferably just before the point where the high-frequency bias is
added). If that is clean, suspect there is poor contact between the
head and the tape. The head-tape contact is far more critical on record >than on playback. If the bias is varying, that can cause all sorts of >problems but that is much less likely to be happening. Frequency >modulation of the sound by tape head squeal is another possibility, >especially with new tape that might have a manufacturing defect, or very >old tape that has begun to deteriorate.
Dirty contacts in the record/playback switch can manifest themselves as >variations in signal level and distortion and are more likley to occur
in a machine that hasn't been used for recording for a long period.. >....But, the head-tape contact should be your first suspect.
My previous remarks about distortion being much easier to detect by >listening, rather than with an oscilloscope, still apply. If you have a >sinewave signal generator, that will make it much easier to hear
distortion than trying to spot subtle changes by listening to programme >material.
Thinking about your very valid suggestion about using the sound rather
than looking at a waveform, I'm guessing a crystal earpiece would work
just as well rather than making up a hi-z probe+ amp would it not?
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 22:25:54 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 20:17:23 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Sat, 10 Jan 2026 18:12:35 +0000, liz@poppyrecords.invalid.invalid >> >> >> (Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like >> >> >> >> your opinion. There's a problem with the audio amplifier chain.
I've eliminated all other possible causes like dirty heads or
faulty tape etc etc. So when I'm listening to playback, the
quality is frequently varying from 'pretty good' to 'really quite >> >> >> >> crappy'
Does it become good and bad at the same places each time you play
the same tape? If it does, the problen is in the recording.
Yes it does. But that recording still had to be processed through
the amp chain.
I can't follow your logic. If the tape sounds good in some places and >> >> >distorted in others - and these are the the same places each time you
play it - the fault is clearly something to do with the tape and not
the amplifier.
Makes no sense to me, that observation. The tape is brand new and from
a well-respected manufacturer. Think about it, the signal on the tape
didn't get 'impressed' there direct from a microphone or whatever, it
had to be amplified. It had to pass through the amplifier chain and be
mixed with the output from the bias oscillator, so whatever defects
were present at that moment from moment to moment from the amp as the
tape passed, will be faithfully recorded and re-playable. I assume
we're not on the same page, so will not address your follow-up until
we're straight on this one.
My apologies, I was assuming you were playng back a tape that had been
recorded some time ago and it had recently begun sounding distorted. I
hadn't realised you were looking for the cause of distortion in the
*recording* amplifier.
In that case you need to monitor the signal going to the recording head
(preferably just before the point where the high-frequency bias is
added). If that is clean, suspect there is poor contact between the
head and the tape. The head-tape contact is far more critical on record
than on playback. If the bias is varying, that can cause all sorts of
problems but that is much less likely to be happening. Frequency
modulation of the sound by tape head squeal is another possibility,
especially with new tape that might have a manufacturing defect, or very
old tape that has begun to deteriorate.
Dirty contacts in the record/playback switch can manifest themselves as
variations in signal level and distortion and are more likley to occur
in a machine that hasn't been used for recording for a long period..
....But, the head-tape contact should be your first suspect.
My previous remarks about distortion being much easier to detect by
listening, rather than with an oscilloscope, still apply. If you have a
sinewave signal generator, that will make it much easier to hear
distortion than trying to spot subtle changes by listening to programme
material.
Thinking about your very valid suggestion about using the sound rather
than looking at a waveform, I'm guessing a crystal earpiece would work
just as well rather than making up a hi-z probe+ amp would it not?
You really need something that gives good sound quality so that you can
hear the difference when the distortion occurs. My experience of most >high-sensitivity earpieces siggests that they could give more distortion
on undistorted signals than the distortion you are listening for - so
you may not hear much difference.
If your distortion is really gross and isn't likely to be caused by the >loading of the amplifier by the earpiece itself, you might be able to
hear it and track it down by that method. Although crystal earpieces
may read open-circuit on a DC test, they have a fair bit of capacitance
and long leads, which could upset the circuit you are trying to monitor.
You haven't really described the distortion but if it sounds like harsh >bursts of sound on loud notes with almost silence in between, that is
usually an indication of a weak or failed bias oscillator. Overloading
the recording gives very sudden onset of bad distortion on loud peaks,
so watch your recording level meter closely (assuming it is correctly >calibrated).
[OT]
Overloading would have much worse consequences if you were disc
recording; it may cause groove inter-cutting, which renders the disc
useless, or it may set fire to the cutterhead which will cost a few
weeks wages to repair (if the nitrate swarf doesn't catch fire too). As
most professional tape recording engineers either began their careers
with disc cutting or worked with disc-cutting engineers, watching the
meter becomes second nature. Turning down the volume control as soon as
the recording has finished is another useful habit, to prevent loud
studio noises from blowing up the cutterhead when not actually
recording.
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's
been played with a worn stylus. Then a few minutes later it might be
fine again - for a while.
I made up a test tape of a 5khz sine wave using my Ferrograph deck and
played it on the Uher. I could hear the distinct difference in quality cutting in and out periodically when I played it back. I then tried to
make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on
high quality audio recordings.
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy' and I'll expand on
what I mean by that. There's a distortion which comes and goes intermittently. You know how vinyl records start off life being really
great sounding, but that gets progressively worse the more times
they're played? Now imagine if you will a vinyl record which has been
played repeatedly with a worn stylus until the recording is very
noticeably impaired; scratchy and gritty sounding and you will have a
good sense of the kind of distortion we're talking about here. What,
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Cheers,
CD
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's
been played with a worn stylus. Then a few minutes later it might be
fine again - for a while.
That distortion is a combination of intermodulation and
noise-behind-signal. Really severe tape squeal is the only thing I can
think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and
played it on the Uher. I could hear the distinct difference in quality
cutting in and out periodically when I played it back. I then tried to
make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on
high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played
back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier,
2 ) shows the problem isn't in the Ferrograph recording amplifier and 1) >shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines >(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past
the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators
have an output impedance around 600 ohms and most Uhers have inputs of
around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is
10 Kc/s which you may not be able to hear and which won't be recorded at
any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present,
but you wouldn't get them from a single sinewave tone.) I would have
chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
On 10/01/2026 16:35, Cursitor Doom wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your
opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy' and I'll expand on
what I mean by that. There's a distortion which comes and goes
intermittently. You know how vinyl records start off life being really
great sounding, but that gets progressively worse the more times
they're played? Now imagine if you will a vinyl record which has been
played repeatedly with a worn stylus until the recording is very
noticeably impaired; scratchy and gritty sounding and you will have a
good sense of the kind of distortion we're talking about here. What,
in your considered opinion, is the most likely cause of this problem
and how would you go about identifying the culprit? Distorted output's
a lot trickier than a break in the signal path to track down!
Cheers,
CD
Thoroughly clean the pinchwheel. It could be accumalating microscopic
bits of ferrite embedded in the rubber. Chech one of the tapes on
another machine as if that is the case you will be corrupting all your
tapes each time you play them as the ferrite is in a sense recording or >deleting microscopically on each passage
On Mon, 12 Jan 2026 10:34:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's
been played with a worn stylus. Then a few minutes later it might be
fine again - for a while.
That distortion is a combination of intermodulation and >noise-behind-signal. Really severe tape squeal is the only thing I can >think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and
played it on the Uher. I could hear the distinct difference in quality
cutting in and out periodically when I played it back. I then tried to
make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on
high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played >back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier,
2 ) shows the problem isn't in the Ferrograph recording amplifier and 1) >shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines >(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past >the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators
have an output impedance around 600 ohms and most Uhers have inputs of >around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is
10 Kc/s which you may not be able to hear and which won't be recorded at >any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present,
but you wouldn't get them from a single sinewave tone.) I would have >chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
Thank you for your observations. I had hoped to devote some time to
this issue today, but other events kind of took over, so the next slot
will be Weds afternoon.
It's a real nuisance not being able to record the test tone on the
Uher. I'm surprised as well. In fact I'm wondering if there's
something else going on there.
I'm going to follow up on your suggestion of cobbling together a hi-z
amp for probing stage-by-stage. I think I've got some FET front-ended
audio op amps somewhere in my parts stash which should be ideal for
this purpose. Can't recall what I originally bought them for, but
whatever it was never got finished, clearly!
I did notice that for some reason on the slowest speed (the 15/16"ips) there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech
just sounds normal and at that speed, it's really only speech that one
would use it for anyway.
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 12 Jan 2026 10:34:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's
been played with a worn stylus. Then a few minutes later it might be
fine again - for a while.
That distortion is a combination of intermodulation and
noise-behind-signal. Really severe tape squeal is the only thing I can
think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and
played it on the Uher. I could hear the distinct difference in quality
cutting in and out periodically when I played it back. I then tried to
make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on
high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played
back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier,
2 ) shows the problem isn't in the Ferrograph recording amplifier and 1)
shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines
(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past
the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators
have an output impedance around 600 ohms and most Uhers have inputs of
around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is
10 Kc/s which you may not be able to hear and which won't be recorded at
any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present,
but you wouldn't get them from a single sinewave tone.) I would have
chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
Thank you for your observations. I had hoped to devote some time to
this issue today, but other events kind of took over, so the next slot
will be Weds afternoon.
It's a real nuisance not being able to record the test tone on the
Uher. I'm surprised as well. In fact I'm wondering if there's
something else going on there.
Have you got the correct connections to the input socket?
I'm going to follow up on your suggestion of cobbling together a hi-z
amp for probing stage-by-stage. I think I've got some FET front-ended
audio op amps somewhere in my parts stash which should be ideal for
this purpose. Can't recall what I originally bought them for, but
whatever it was never got finished, clearly!
Easier than that: connect a piece of screened cable to the input of an >amplifier with reasonable gain and make a probe from a 1 megohm resistor
in series with a 10 nf capacitor at the free end. For an earth
connection you can use a crocodile clip, either on the end of a long
piece of wire coming from the amplifier or on a shorter piece connected
to the screen of the cable.
I did notice that for some reason on the slowest speed (the 15/16"ips)
there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech
just sounds normal and at that speed, it's really only speech that one
would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips >wouldn't normally be used for music. 3+3/4 ips is the bare minimum for >domestic music and 7+1/2 ips is the minimum for professional recording.
I recorded a few folk music items at 7+1/2 ips for local radio and they
were happy enough with that - but for orchestral music nothing less than
15 ips was considered good enough for mainstream radio.
The speed variation could be caused by dirt on the surface of the
capstan or pinch wheel, or their bearings could be getting a bit tight >(unlikely for the capstan). The pinch wheel or the tyre of the flywheel >could be a bit dirty or oily - or it could have an indentation where the >machine has been left 'in gear' with the motor not running for long
period of storage. Other casues include dragging friction clutches, >unevenly-wound spools and binding in the guides.
The frequency of the speed variations and their 'waveform' can often
give a clue to their cause. Does the speed vary smoothly and
sinusoidally (unven pinch wheel) or does it 'hiccup' slightly (dirt or >indentations)? Watch the rotating components and try to work out which
one's rotation corresponds to the speed of variation.
On Tue, 13 Jan 2026 09:46:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 12 Jan 2026 10:34:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's >> >> been played with a worn stylus. Then a few minutes later it might be
fine again - for a while.
That distortion is a combination of intermodulation and
noise-behind-signal. Really severe tape squeal is the only thing I can >> >think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and >> >> played it on the Uher. I could hear the distinct difference in quality >> >> cutting in and out periodically when I played it back. I then tried to >> >> make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on >> >> high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played >> >back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier, >> >2 ) shows the problem isn't in the Ferrograph recording amplifier and 1) >> >shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines >> >(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past >> >the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators
have an output impedance around 600 ohms and most Uhers have inputs of
around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is >> >10 Kc/s which you may not be able to hear and which won't be recorded at >> >any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present,
but you wouldn't get them from a single sinewave tone.) I would have
chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
Thank you for your observations. I had hoped to devote some time to
this issue today, but other events kind of took over, so the next slot
will be Weds afternoon.
It's a real nuisance not being able to record the test tone on the
Uher. I'm surprised as well. In fact I'm wondering if there's
something else going on there.
Have you got the correct connections to the input socket?
Yes, but there's an adaptor inline that could be the cause of it. I'll investigate that tomorrow. One of the really old Chinese things: prime suspect. Chinese stuff continues to improve, but god knows it was
*crap* 20 years ago and sadly some of it still is (but far less
prevalent).
I'm going to follow up on your suggestion of cobbling together a hi-z
amp for probing stage-by-stage. I think I've got some FET front-ended
audio op amps somewhere in my parts stash which should be ideal for
this purpose. Can't recall what I originally bought them for, but
whatever it was never got finished, clearly!
Easier than that: connect a piece of screened cable to the input of an >amplifier with reasonable gain and make a probe from a 1 megohm resistor
in series with a 10 nf capacitor at the free end. For an earth
connection you can use a crocodile clip, either on the end of a long
piece of wire coming from the amplifier or on a shorter piece connected
to the screen of the cable.
Delightfully old school. I like it! What you're describing sounds
rather like an oscilloscope probe - except with much higher
capacitance. Shame as a scope probe is very ergonomic and ideal for
this kind of poking around.
I did notice that for some reason on the slowest speed (the 15/16"ips)
there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech
just sounds normal and at that speed, it's really only speech that one
would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips >wouldn't normally be used for music. 3+3/4 ips is the bare minimum for >domestic music and 7+1/2 ips is the minimum for professional recording.
I recorded a few folk music items at 7+1/2 ips for local radio and they >were happy enough with that - but for orchestral music nothing less than
15 ips was considered good enough for mainstream radio.
So you're saying the speed's varying at all the higher speeds as well,
then? I guess that would make sense given the relatively agricultural mechanics of these old decks, but I still can't hear such a wobble at
any of the 3 higher speeds. I suppose a frequency counter and test
tape would be the answer to finding out more about that.
The speed variation could be caused by dirt on the surface of the
capstan or pinch wheel, or their bearings could be getting a bit tight >(unlikely for the capstan). The pinch wheel or the tyre of the flywheel >could be a bit dirty or oily - or it could have an indentation where the >machine has been left 'in gear' with the motor not running for long
period of storage. Other casues include dragging friction clutches, >unevenly-wound spools and binding in the guides.
The frequency of the speed variations and their 'waveform' can often
give a clue to their cause. Does the speed vary smoothly and
sinusoidally (unven pinch wheel) or does it 'hiccup' slightly (dirt or >indentations)? Watch the rotating components and try to work out which >one's rotation corresponds to the speed of variation.
I haven't been able to tell - but I haven't tried the constant tone
test tape yet. That will show it up much more clearly and that's what
I intend to do tomorrow...
... if I can nail the distortion issue, which is
the more significant problem right now.
On 10/01/2026 16:35, Cursitor Doom wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your
opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy' and I'll expand on
what I mean by that. There's a distortion which comes and goes
Cursitor Doom <cd@notformail.com> wrote:
On 10/01/2026 16:35, Cursitor Doom wrote:
Hi all,
I've identified an issue with my Uher tape recorder and I'd like your >>>> opinion. There's a problem with the audio amplifier chain. I've
eliminated all other possible causes like dirty heads or faulty tape
etc etc. So when I'm listening to playback, the quality is frequently
varying from 'pretty good' to 'really quite crappy' and I'll expand on >>>> what I mean by that. There's a distortion which comes and goes
Long ago I was given a Harman Kardon 505 amp.
It occasionally seemed to "lock up" at full DC output on one channel.
With a colleague reading off test voltages from the schematic I probed
the circuit, eventually getting to the tone controls. The solder joints
all looked perfect, beautiful fillets, no dewets. The meter probe touched
a lead (I think from a transistor) and the lead slipped in the fillet!
Apparently the plating had corroded or otherwise released the transistor >lead. I reflowed the solder joint (and maybe a few others, don't remember) >and the amp is still working 30 years later.
The surprise wasn't so much the faulty joint but the visual perfection of
the fault. I'm not at all certain the story is relevant to the problem at >hand, but if all else fails a "push test" on the solder joints in the
record amp chain might be worth a try.
Thanks for reading,
bob prohaska
Cursitor Doom <cd@notformail.com> wrote:
On Tue, 13 Jan 2026 09:46:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 12 Jan 2026 10:34:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's >> >> >> been played with a worn stylus. Then a few minutes later it might be >> >> >> fine again - for a while.
That distortion is a combination of intermodulation and
noise-behind-signal. Really severe tape squeal is the only thing I can >> >> >think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and >> >> >> played it on the Uher. I could hear the distinct difference in quality >> >> >> cutting in and out periodically when I played it back. I then tried to >> >> >> make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on >> >> >> high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played >> >> >back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier, >> >> >2 ) shows the problem isn't in the Ferrograph recording amplifier and 1) >> >> >shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines >> >> >(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past >> >> >the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators >> >> >have an output impedance around 600 ohms and most Uhers have inputs of >> >> >around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is >> >> >10 Kc/s which you may not be able to hear and which won't be recorded at >> >> >any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present, >> >> >but you wouldn't get them from a single sinewave tone.) I would have >> >> >chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
Thank you for your observations. I had hoped to devote some time to
this issue today, but other events kind of took over, so the next slot
will be Weds afternoon.
It's a real nuisance not being able to record the test tone on the
Uher. I'm surprised as well. In fact I'm wondering if there's
something else going on there.
Have you got the correct connections to the input socket?
Yes, but there's an adaptor inline that could be the cause of it. I'll
investigate that tomorrow. One of the really old Chinese things: prime
suspect. Chinese stuff continues to improve, but god knows it was
*crap* 20 years ago and sadly some of it still is (but far less
prevalent).
I'm going to follow up on your suggestion of cobbling together a hi-z
amp for probing stage-by-stage. I think I've got some FET front-ended
audio op amps somewhere in my parts stash which should be ideal for
this purpose. Can't recall what I originally bought them for, but
whatever it was never got finished, clearly!
Easier than that: connect a piece of screened cable to the input of an
amplifier with reasonable gain and make a probe from a 1 megohm resistor
in series with a 10 nf capacitor at the free end. For an earth
connection you can use a crocodile clip, either on the end of a long
piece of wire coming from the amplifier or on a shorter piece connected
to the screen of the cable.
Delightfully old school. I like it! What you're describing sounds
rather like an oscilloscope probe - except with much higher
capacitance. Shame as a scope probe is very ergonomic and ideal for
this kind of poking around.
The capacitance I am suggesting is in series with the signal to stop any
DC from getting into the test amplifier. The capacitance quoted for >oscilloscopes and probes is the shunt capacitance from signal to earth.
You could use an oscillocope probe if you have one with a suitable plug,
but interpose a 10nf capacitor between the probe tip and the point in
the circuit you are measuring, so as to block any DC.
If you want an ergonomic probe, put the components into a ball-point pen
case (if you can find a small enough capacitor). ...or just put the
resistor in the pen case and have the capacitor in the plug at the
amplifier end of the cable.
I have a home-built test amplifier screwed to the underside of the shelf >above the workshop bench, with a veriety of input connectors and probes.
It has two attenuators calibrated in 10 and 1 dB steps, with a meter
that reads directly in dB or can be switched with an electronic zero to
read variations of 0.1 dB. There is an output at 0dBm level for
feeding external equipment, such as high-quality headphones or an >oscilloscope, and it has a small loudspeaker, which is often more use
than the oscilloscope for identifying the cause of fault.
I did notice that for some reason on the slowest speed (the 15/16"ips)
there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech
just sounds normal and at that speed, it's really only speech that one
would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips
wouldn't normally be used for music. 3+3/4 ips is the bare minimum for
domestic music and 7+1/2 ips is the minimum for professional recording.
I recorded a few folk music items at 7+1/2 ips for local radio and they
were happy enough with that - but for orchestral music nothing less than
15 ips was considered good enough for mainstream radio.
So you're saying the speed's varying at all the higher speeds as well,
then? I guess that would make sense given the relatively agricultural
mechanics of these old decks, but I still can't hear such a wobble at
any of the 3 higher speeds. I suppose a frequency counter and test
tape would be the answer to finding out more about that.
At higher speeds the flywheel effect of the rotating components is much >greater and any given actual speed variation is a smaller percentage of
the faster running speed - so both effect improve the overall speed >stability.
Hiccups due to dirt on the capstan will be the same magnitude at all
speeds but will occur at a faster rate at higher capstan and tape
speeds..
The speed variation could be caused by dirt on the surface of the
capstan or pinch wheel, or their bearings could be getting a bit tight
(unlikely for the capstan). The pinch wheel or the tyre of the flywheel
could be a bit dirty or oily - or it could have an indentation where the
machine has been left 'in gear' with the motor not running for long
period of storage. Other casues include dragging friction clutches,
unevenly-wound spools and binding in the guides.
The frequency of the speed variations and their 'waveform' can often
give a clue to their cause. Does the speed vary smoothly and
sinusoidally (unven pinch wheel) or does it 'hiccup' slightly (dirt or
indentations)? Watch the rotating components and try to work out which
one's rotation corresponds to the speed of variation.
I haven't been able to tell - but I haven't tried the constant tone
test tape yet. That will show it up much more clearly and that's what
I intend to do tomorrow...
Remember, the wow could be coming from the machine that recorded the
tape, so try recording one on each machine and playing them both back on
one machine - does the wow and flutter sound the same for both
recordings or different? Then try the same test for one recording
played back on both machines.
If you can remember what you are doing without getting muddled (a
notepad might help) you may be able to draw some useful conclusions
about which machine is causing which effect. Don't expect to make sense
of this when you are tired or have other things on your mind.
... if I can nail the distortion issue, which is
the more significant problem right now.
You will be lucky to record 5Kc/s steadily at 15/16 ips. and you are
unlikely to hear harmonic distortion from it at any tape speed. If you
can hear something that sounds like distortion on a 5Kc/s tone, it is
almost certainly not waveform distortion but more probably something
else, like noise behind signal . If it contains lower frequency
components than the initial tone it might be due to intermodulation, but
that ought not to occur on a single sinewave. Try 630c/s and see if the >results are different.
On Wed, 14 Jan 2026 11:30:29 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
The capacitance I am suggesting is in series with the signal to stop any
DC from getting into the test amplifier. The capacitance quoted for >oscilloscopes and probes is the shunt capacitance from signal to earth.
You could use an oscillocope probe if you have one with a suitable plug, >but interpose a 10nf capacitor between the probe tip and the point in
the circuit you are measuring, so as to block any DC.
Oh dear. Here's the probe I made up today. Can you spot where I went
wrong? Sigh.....
https://disk.yandex.com/i/fzGLE2MZltBpQQ
Cursitor Doom <cd@notformail.com> wrote:
On Tue, 13 Jan 2026 09:46:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Mon, 12 Jan 2026 10:34:12 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
[...]
No, it's not coming in bursts. As I said in my original post, it
really does sound for all the world like an old 45 vinyl record that's >> >> >> been played with a worn stylus. Then a few minutes later it might be >> >> >> fine again - for a while.
That distortion is a combination of intermodulation and
noise-behind-signal. Really severe tape squeal is the only thing I can >> >> >think of that sounds like that on a tape recording
I made up a test tape of a 5khz sine wave using my Ferrograph deck and >> >> >> played it on the Uher. I could hear the distinct difference in quality >> >> >> cutting in and out periodically when I played it back. I then tried to >> >> >> make another test tape of the same tone on the Uher to play back on
the F'graph, but didn't have sufficiently low source impedance from
the generator in this instance so I had to use a radio broadcast
instead. Not ideal, but the distortion is still readily noticeable on >> >> >> high quality audio recordings.
Have I understood this correctly?
1) A tape recorded on the Ferrograph shows intermittent distortion
when it is played back on the Uher.
2) A tape recorded on the Uher shows similar intermittent distortion
when played back on the Ferrograph.
3) The distortion occurs at the same place each time the tape is played >> >> >back and isn't related to signal level.
By elimination: 3) rules out any problems in either playback amplifier, >> >> >2 ) shows the problem isn't in the Ferrograph recording amplifier and 1) >> >> >shows the problem isn't in the Uher recording amplifier. The only
things left are the tape itself or one of the transports.
Years ago there were problems when one or two tape manufacturers
produced tape with a backing that caused squeal in pressure-pad machines >> >> >(which both the Uher and the Ferrograph are) but you would be able to
hear that by turning down the sound and listening to the tape going past >> >> >the heads.
I'm surprised the signal generator didn't have low enough source
impedance to feed a signal into the Uher; most audio signal generators >> >> >have an output impedance around 600 ohms and most Uhers have inputs of >> >> >around 600 ohms and 'high' (around 47k).
Why were you using 5Kc/s as your test tone? The second harmonic of
that, which is the first spurious frequency created by distortion, is >> >> >10 Kc/s which you may not be able to hear and which won't be recorded at >> >> >any tape speed below 7.5 ips. (Intermodulation distortion would be
audible as spurious low frequencies if there were other tones present, >> >> >but you wouldn't get them from a single sinewave tone.) I would have >> >> >chosen something around the middle of the audio band e.g. 630c/s so
the harmonics fell in the area of the greatest hearing sensitivity.
Thank you for your observations. I had hoped to devote some time to
this issue today, but other events kind of took over, so the next slot
will be Weds afternoon.
It's a real nuisance not being able to record the test tone on the
Uher. I'm surprised as well. In fact I'm wondering if there's
something else going on there.
Have you got the correct connections to the input socket?
Yes, but there's an adaptor inline that could be the cause of it. I'll
investigate that tomorrow. One of the really old Chinese things: prime
suspect. Chinese stuff continues to improve, but god knows it was
*crap* 20 years ago and sadly some of it still is (but far less
prevalent).
I'm going to follow up on your suggestion of cobbling together a hi-z
amp for probing stage-by-stage. I think I've got some FET front-ended
audio op amps somewhere in my parts stash which should be ideal for
this purpose. Can't recall what I originally bought them for, but
whatever it was never got finished, clearly!
Easier than that: connect a piece of screened cable to the input of an
amplifier with reasonable gain and make a probe from a 1 megohm resistor
in series with a 10 nf capacitor at the free end. For an earth
connection you can use a crocodile clip, either on the end of a long
piece of wire coming from the amplifier or on a shorter piece connected
to the screen of the cable.
Delightfully old school. I like it! What you're describing sounds
rather like an oscilloscope probe - except with much higher
capacitance. Shame as a scope probe is very ergonomic and ideal for
this kind of poking around.
The capacitance I am suggesting is in series with the signal to stop any
DC from getting into the test amplifier. The capacitance quoted for >oscilloscopes and probes is the shunt capacitance from signal to earth.
You could use an oscillocope probe if you have one with a suitable plug,
but interpose a 10nf capacitor between the probe tip and the point in
the circuit you are measuring, so as to block any DC.
If you want an ergonomic probe, put the components into a ball-point pen
case (if you can find a small enough capacitor). ...or just put the
resistor in the pen case and have the capacitor in the plug at the
amplifier end of the cable.
I have a home-built test amplifier screwed to the underside of the shelf >above the workshop bench, with a veriety of input connectors and probes.
It has two attenuators calibrated in 10 and 1 dB steps, with a meter
that reads directly in dB or can be switched with an electronic zero to
read variations of 0.1 dB. There is an output at 0dBm level for
feeding external equipment, such as high-quality headphones or an >oscilloscope, and it has a small loudspeaker, which is often more use
than the oscilloscope for identifying the cause of fault.
I did notice that for some reason on the slowest speed (the 15/16"ips)
there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech
just sounds normal and at that speed, it's really only speech that one
would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips
wouldn't normally be used for music. 3+3/4 ips is the bare minimum for
domestic music and 7+1/2 ips is the minimum for professional recording.
I recorded a few folk music items at 7+1/2 ips for local radio and they
were happy enough with that - but for orchestral music nothing less than
15 ips was considered good enough for mainstream radio.
So you're saying the speed's varying at all the higher speeds as well,
then? I guess that would make sense given the relatively agricultural
mechanics of these old decks, but I still can't hear such a wobble at
any of the 3 higher speeds. I suppose a frequency counter and test
tape would be the answer to finding out more about that.
At higher speeds the flywheel effect of the rotating components is much >greater and any given actual speed variation is a smaller percentage of
the faster running speed - so both effect improve the overall speed >stability.
Hiccups due to dirt on the capstan will be the same magnitude at all[...]
speeds but will occur at a faster rate at higher capstan and tape
speeds..
Remember, the wow could be coming from the machine that recorded the
tape, so try recording one on each machine and playing them both back on
one machine - does the wow and flutter sound the same for both
recordings or different? Then try the same test for one recording
played back on both machines.
If you can remember what you are doing without getting muddled (a
notepad might help) you may be able to draw some useful conclusions
about which machine is causing which effect. Don't expect to make sense
of this when you are tired or have other things on your mind.
... if I can nail the distortion issue, which is
the more significant problem right now.
You will be lucky to record 5Kc/s steadily at 15/16 ips. and you are
unlikely to hear harmonic distortion from it at any tape speed. If you
can hear something that sounds like distortion on a 5Kc/s tone, it is
almost certainly not waveform distortion but more probably something
else, like noise behind signal . If it contains lower frequency
components than the initial tone it might be due to intermodulation, but
that ought not to occur on a single sinewave. Try 630c/s and see if the >results are different.
On Wed, 14 Jan 2026 11:30:29 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
If you want an ergonomic probe, put the components into a ball-point pen >case (if you can find a small enough capacitor). ...or just put the >resistor in the pen case and have the capacitor in the plug at the >amplifier end of the cable.
I'll get the probe I improvised re-jigged, but won't have time to do
any more to the Uher til Sunday, unfortunately.
I have a home-built test amplifier screwed to the underside of the shelf >above the workshop bench, with a veriety of input connectors and probes.
It has two attenuators calibrated in 10 and 1 dB steps, with a meter
that reads directly in dB or can be switched with an electronic zero to >read variations of 0.1 dB. There is an output at 0dBm level for
feeding external equipment, such as high-quality headphones or an >oscilloscope, and it has a small loudspeaker, which is often more use
than the oscilloscope for identifying the cause of fault.
Yes, I'm sure you're right and it sounds like you have everything
organized so well at your workshop. You do this kind of thing for a
living? I'm just a hobbyist and not exactly outstanding at this if I'm
honest about it. My workbench is an absolute disgrace. I just use up
all horizontal space that's free in next to no time; always been the
same.
I did notice that for some reason on the slowest speed (the 15/16"ips) >> >> there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's
all about. Fortunately, it's only music where it's noticeable; speech >> >> just sounds normal and at that speed, it's really only speech that one >> >> would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips >> >wouldn't normally be used for music. 3+3/4 ips is the bare minimum for >> >domestic music and 7+1/2 ips is the minimum for professional recording. >> >I recorded a few folk music items at 7+1/2 ips for local radio and they >> >were happy enough with that - but for orchestral music nothing less than >> >15 ips was considered good enough for mainstream radio.
So you're saying the speed's varying at all the higher speeds as well,
then? I guess that would make sense given the relatively agricultural
mechanics of these old decks, but I still can't hear such a wobble at
any of the 3 higher speeds. I suppose a frequency counter and test
tape would be the answer to finding out more about that.
At higher speeds the flywheel effect of the rotating components is much >greater and any given actual speed variation is a smaller percentage of
the faster running speed - so both effect improve the overall speed >stability.
Right, so the increased inertia helps to stabilize the speed? That
makes sense. I assume those flywheels are so heavy for the same reason
(tape deck flywheels, I mean).
Hiccups due to dirt on the capstan will be the same magnitude at all[...]
speeds but will occur at a faster rate at higher capstan and tape
speeds..
Remember, the wow could be coming from the machine that recorded the
tape, so try recording one on each machine and playing them both back on >one machine - does the wow and flutter sound the same for both
recordings or different? Then try the same test for one recording
played back on both machines.
Well that's what I'd been attempting to do when I failed to get the
signal generator output into the Uher's audio input. As I mentioned, I suspected it was the cheap Chinese adaptor I'd been using. So I made
up another one (also shown in the picture). Not very pretty and could
have been constructed more thoughtfully, but will get the job done, no
doubt.
Try 630c/s and see if the
results are different.
I can do 630hz for sure, but why so specific a frequency?
I also made another discovery about the possible cause of the varying
speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO mention of this in the owner's handbook! It does say that the machine
should not be left unattended for long periods switched off with the
'play' key left depressed, but that's pretty much common sense. I only
became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone demonstrating this deck. Consequently, I'd been leaving the machine in
this state when unused and I would put money that previous owners have
done the same thing during their ownership too. So there may well be
multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Cursitor Doom <cd@notformail.com> wrote:
On Wed, 14 Jan 2026 11:30:29 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
[...]
If you want an ergonomic probe, put the components into a ball-point pen
case (if you can find a small enough capacitor). ...or just put the
resistor in the pen case and have the capacitor in the plug at the
amplifier end of the cable.
I'll get the probe I improvised re-jigged, but won't have time to do
any more to the Uher til Sunday, unfortunately.
Just a minor point:
It doesn't look as though there will be room for the capacitor inside
the plug where it will be screened, so the capacitor needs to be at the
tip of the probe with the resistor between it and the cable end. This
is so that the resistor attenuates any stray signals picked up by the >capacitor. If the capacitor were on the amplifier side of the resistor, >anything it picked up from the mains or the proximity of your hand,
acting like an aerial, would be fully amplified.
I have a home-built test amplifier screwed to the underside of the shelf
above the workshop bench, with a veriety of input connectors and probes.
It has two attenuators calibrated in 10 and 1 dB steps, with a meter
that reads directly in dB or can be switched with an electronic zero to
read variations of 0.1 dB. There is an output at 0dBm level for
feeding external equipment, such as high-quality headphones or an
oscilloscope, and it has a small loudspeaker, which is often more use
than the oscilloscope for identifying the cause of fault.
Yes, I'm sure you're right and it sounds like you have everything
organized so well at your workshop. You do this kind of thing for a
living? I'm just a hobbyist and not exactly outstanding at this if I'm
honest about it. My workbench is an absolute disgrace. I just use up
all horizontal space that's free in next to no time; always been the
same.
My workshop is a 6ft x 10ft wooden shed containing dreadful mixture of >amateur, semi-professional and fully professional work in several
different fields. The welding and blacksmithing can only take place
outside in good weather and the Harrison L5 lathe is in a spare
downstairs room in the house.
The workbench is a matted tangle of wire clippings and bits; I have to
clear a space to bring in things I need to work on. Anything too big
has to be dismantled on the kitchen table, then taken to the shed and
worked on in sections - or the oscilloscope and soldering iron have to
be taken to the kitchen. That means a very thorough clean-up in the
kitchen before I can do any pastry-making.
The equipment comprises a large Solartron (valve) audio signal
generator, a Marconi (valve) RF -VHF signal generator. The
aforementioned measuring amplifier, a Philips twin-trace oscilloscope
and several Farnell power supplies: 0-30v, 50-0-50v and 0-350v. I have
a few resistance boxes and capacitance boxes for experimental work. For
the bench mains supply there is a variac-controlled isolation
transformer with 240v and 120v tappings. Other equipment is scattered
around the house in odd corners and can be brought into the shed when it
is needed.
One long wall is covered with nests of drawers containing resistors and >capacitors, laid out on a grid pattern with preferred values aligned >horizontally and the decades in vertical columns. Drums of wire are
stored on broom handles hung in strops from the ceiling. The end of the
shed nearest the doorhas a cabinet and a bench with the welding,
metalworking and car repair tools. Small shelves along the tops of the
walls house everything from transformers to household nails and spare
rivets with a rivetting set for the Allen Scythe cutterbar!
I did notice that for some reason on the slowest speed (the 15/16"ips) >> >> >> there's considerable variation in the tonal reproduction with music
off the radio, as if the speed is wandering during transport. Not
noticed any such effect at the higher speeds so not sure what that's >> >> >> all about. Fortunately, it's only music where it's noticeable; speech >> >> >> just sounds normal and at that speed, it's really only speech that one >> >> >> would use it for anyway.
Speed variations are much more obvious at slower tape speeds, 15/16 ips >> >> >wouldn't normally be used for music. 3+3/4 ips is the bare minimum for >> >> >domestic music and 7+1/2 ips is the minimum for professional recording. >> >> >I recorded a few folk music items at 7+1/2 ips for local radio and they >> >> >were happy enough with that - but for orchestral music nothing less than >> >> >15 ips was considered good enough for mainstream radio.
So you're saying the speed's varying at all the higher speeds as well,
then? I guess that would make sense given the relatively agricultural
mechanics of these old decks, but I still can't hear such a wobble at
any of the 3 higher speeds. I suppose a frequency counter and test
tape would be the answer to finding out more about that.
A counter may not show up the problem because it averages the frequency
over a period of time. A "wow-and-flutter meter" is the right thing to
use but, being specialised, they are not very common. Ferrograph made a
test set with all the necessary instruments built-in but they tend to be >collectors' items and will probably need repair themselves before they
can be used. Human ears work quite well on suitable recorded material.
At higher speeds the flywheel effect of the rotating components is much
greater and any given actual speed variation is a smaller percentage of
the faster running speed - so both effect improve the overall speed
stability.
Right, so the increased inertia helps to stabilize the speed? That
makes sense. I assume those flywheels are so heavy for the same reason
(tape deck flywheels, I mean).
The slower the flywheel, the heavier it needs to be - with the mass >concentrated as near to the rim as possible. In the Uher, the capstan
shaft has only a very lightweight driving wheel that rotates slowly, so
the inertia of that is negligible. The speed,stabilising inertia is in
a heavy brass flywheel on the cross-shaft, which rotates much faster and >friction-drives the lightweight wheel through a rubber tyre on the
latter. It is vital that this rubber tyre is in good condition, because
any notches or lumps will tend to deflect the speed of the lightweight >driving wheel (and the capstan) rather than being absorbed in the speed
of the brass flywheel.
That is why disengaging the drive when the machine is being stored is
very important.
Hiccups due to dirt on the capstan will be the same magnitude at all[...]
speeds but will occur at a faster rate at higher capstan and tape
speeds..
Remember, the wow could be coming from the machine that recorded the
tape, so try recording one on each machine and playing them both back on
one machine - does the wow and flutter sound the same for both
recordings or different? Then try the same test for one recording
played back on both machines.
Well that's what I'd been attempting to do when I failed to get the
signal generator output into the Uher's audio input. As I mentioned, I
suspected it was the cheap Chinese adaptor I'd been using. So I made
up another one (also shown in the picture). Not very pretty and could
have been constructed more thoughtfully, but will get the job done, no
doubt.
It looks fine to me. Not all good working equipment needs to look swish
and 'professional' - a lot of my fully-professional recording equipment
is plugged together on site using ex-telephone switchboard jack strips
with exposed wiring (so I can see at a glance what the connections are).
They can always be discretely slid down the back of the table once the
kit is working properly.
[...]
Try 630c/s and see if the
results are different.
I can do 630hz for sure, but why so specific a frequency?
It is geometrically half way between 20c/s and 20Kc/s i.e. the middle of
the audio band. [Try repeatedly dividing it by 2 or multiplying it by 2
on a pocket calculator, you will get to 20Kc/s or 20 c/s in the same
number of operations]
It also has the second harmonic at 1260c/s and the third harmonic at
1890c/s, which lie at the peak of sensitivity of the human ear - so it
is good for detecting the unwanted harmonics arising from waveform >distortion.
I also made another discovery about the possible cause of the varying
speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO
mention of this in the owner's handbook! It does say that the machine
should not be left unattended for long periods switched off with the
'play' key left depressed, but that's pretty much common sense. I only
became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone
demonstrating this deck. Consequently, I'd been leaving the machine in
this state when unused and I would put money that previous owners have
done the same thing during their ownership too. So there may well be
multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Tht is very important and will account for 'hiccupy' speed veriations.
I seem to remember my Uhers needed to be put into the 'neutral' position
to switch off the motor, so the user was unlikely to forget, as they
were acutely aware of the need to conserve battery power on location.
If yours has only been used on a mains adaptor, I can see how the >misunderstanding could have occurred.
On Thu, 15 Jan 2026 11:54:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Just a minor point:
It doesn't look as though there will be room for the capacitor inside
the plug where it will be screened, so the capacitor needs to be at the
tip of the probe with the resistor between it and the cable end. This
is so that the resistor attenuates any stray signals picked up by the >capacitor. If the capacitor were on the amplifier side of the resistor, >anything it picked up from the mains or the proximity of your hand,
acting like an aerial, would be fully amplified.
A fine but important point there! We often think 'stuff in series' can
go in any order, but so often there are exceptions due to unexpected
effects which must be allowed for. I do have some more suitable
sub-min 10n caps which would be much easier to shield. I'll use those
on the Mk II version. :-)
I also made another discovery about the possible cause of the varying
speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO
mention of this in the owner's handbook! It does say that the machine
should not be left unattended for long periods switched off with the
'play' key left depressed, but that's pretty much common sense. I only
became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone
demonstrating this deck. Consequently, I'd been leaving the machine in
this state when unused and I would put money that previous owners have
done the same thing during their ownership too. So there may well be
multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Tht is very important and will account for 'hiccupy' speed veriations.
I seem to remember my Uhers needed to be put into the 'neutral' position
to switch off the motor, so the user was unlikely to forget, as they
were acutely aware of the need to conserve battery power on location.
If yours has only been used on a mains adaptor, I can see how the >misunderstanding could have occurred.
There's no give away 'feel' to it like when you release the 'play' key
you can sense the tension coming off. That doesn't happen with that
knob at all.
Now I have to ask: how and where did you learn all this stuff?
You're
clearly an expert in this field whether you acknowledge it or not and
there are vanishingly few women who go down such a technical pathway, certainly not in the 'old days' at any rate! Did you experience discrimination on account of it? Must have been bloody difficult in an all-male environment.
Cursitor Doom <cd@notformail.com> wrote:
On Thu, 15 Jan 2026 11:54:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
[...]
Just a minor point:
It doesn't look as though there will be room for the capacitor inside
the plug where it will be screened, so the capacitor needs to be at the
tip of the probe with the resistor between it and the cable end. This
is so that the resistor attenuates any stray signals picked up by the
capacitor. If the capacitor were on the amplifier side of the resistor,
anything it picked up from the mains or the proximity of your hand,
acting like an aerial, would be fully amplified.
A fine but important point there! We often think 'stuff in series' can
go in any order, but so often there are exceptions due to unexpected
effects which must be allowed for. I do have some more suitable
sub-min 10n caps which would be much easier to shield. I'll use those
on the Mk II version. :-)
Make sure it has a high enough voltage rating if you ever want to
fault-find valve equipment.
[...]
I also made another discovery about the possible cause of the varying
speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO
mention of this in the owner's handbook! It does say that the machine
should not be left unattended for long periods switched off with the
'play' key left depressed, but that's pretty much common sense. I only
became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone
demonstrating this deck. Consequently, I'd been leaving the machine in
this state when unused and I would put money that previous owners have
done the same thing during their ownership too. So there may well be
multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Tht is very important and will account for 'hiccupy' speed veriations.
I seem to remember my Uhers needed to be put into the 'neutral' position
to switch off the motor, so the user was unlikely to forget, as they
were acutely aware of the need to conserve battery power on location.
If yours has only been used on a mains adaptor, I can see how the
misunderstanding could have occurred.
There's no give away 'feel' to it like when you release the 'play' key
you can sense the tension coming off. That doesn't happen with that
knob at all.
The speed selector is a very counter-intuitive thing to operste, it
doesn't make sense until you look inside and see what they are trying to
do with it and how it controls the positioning of the cross-shaft.
Another thing that isn't obvious is that it has a locking mechanism (at
least in some models): if the knob is turned through 90 degrees, the
speed selector can't be moved. There is a line marked on the face of
the knob but it isn't at all obvious what it means. I assume this is to >prevent the motor being accidentally turned on by catching on the
reporter's sleeve when using it on the shoulder strap.
Now I have to ask: how and where did you learn all this stuff?
I'm very old, so I have had a long time to learn it.
You're
clearly an expert in this field whether you acknowledge it or not and
there are vanishingly few women who go down such a technical pathway,
certainly not in the 'old days' at any rate! Did you experience
discrimination on account of it? Must have been bloody difficult in an
all-male environment.
It's more complicated than that: I spent most of my life trying to act
like a man and only recently realised I had been a transwoman all
along. This meant that I didn't experience the same obstacles a woman
would have met but, instead, I was constantly bullied for not being
'manly' enough. Luckily my two parallel careers were in electronics and >biology, biology has always been open to women - and to men with a more >feminine outlook on life. Electronics was very mysogenistic to start
with but is becoming more woman-friendly now. My local radio club has
three husband-and-wife pairs of licenced radio amateurs. Most of the
other clubs in this area have at least one open transwoman and some have
a few others still "in the closet" - those statistics would be a good >research project for someone. This is a far cry from the early 1950s,
when Jean Walton had to change her name and persona to John Walton
before Decca would treat her/his electronics and mechanical design
abilities seriously.
I first worked in marine radio design but, when I left that, my main day
job became biology. I continued to have electronics as my hobby and
worked as a sub-contractor to the (UK) National Sound Archive in my
evenings and weekends.
Because I was running the sound recording job on a shoestring, I could
only afford to equip the 'studio' (a bench across the bay window in the
front room) with equipment that had been sold at scrap prices - but my
work had to meet full professional specification. This meant I had to
learn, very quickly, how to rebuild knackered bits of kit back to
factory specification and calibrate them to the satisfaction of my
N.S.A. boss, who was extremely helpful but a stickler for accuracy.
He was a BBC-trained studio manager and recording engineer from the days
when discs were the main medium and he had built his own recording
studio from scratch (with a home-made recording lathe). He acted as my >mentor and most of what I now know in the audio field can be traced back
to his teaching.
Nowadays the first question most people ask, when presented with a
problem, is "what can I buy that will do the job for me". I am still of
the old school that asks "What have I got that can be adapted to do the
job? ...and if I haven't got anything, can I make something?"
On Fri, 16 Jan 2026 10:21:16 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Thu, 15 Jan 2026 11:54:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
[...]
Just a minor point:
It doesn't look as though there will be room for the capacitor inside
the plug where it will be screened, so the capacitor needs to be at the >> >tip of the probe with the resistor between it and the cable end. This
is so that the resistor attenuates any stray signals picked up by the
capacitor. If the capacitor were on the amplifier side of the resistor, >> >anything it picked up from the mains or the proximity of your hand,
acting like an aerial, would be fully amplified.
A fine but important point there! We often think 'stuff in series' can
go in any order, but so often there are exceptions due to unexpected
effects which must be allowed for. I do have some more suitable
sub-min 10n caps which would be much easier to shield. I'll use those
on the Mk II version. :-)
Make sure it has a high enough voltage rating if you ever want to >fault-find valve equipment.
[...]
I also made another discovery about the possible cause of the varying >> >> speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO >> >> mention of this in the owner's handbook! It does say that the machine >> >> should not be left unattended for long periods switched off with the
'play' key left depressed, but that's pretty much common sense. I only >> >> became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone >> >> demonstrating this deck. Consequently, I'd been leaving the machine in >> >> this state when unused and I would put money that previous owners have >> >> done the same thing during their ownership too. So there may well be
multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Tht is very important and will account for 'hiccupy' speed veriations.
I seem to remember my Uhers needed to be put into the 'neutral' position >> >to switch off the motor, so the user was unlikely to forget, as they
were acutely aware of the need to conserve battery power on location.
If yours has only been used on a mains adaptor, I can see how the
misunderstanding could have occurred.
There's no give away 'feel' to it like when you release the 'play' key
you can sense the tension coming off. That doesn't happen with that
knob at all.
The speed selector is a very counter-intuitive thing to operste, it
doesn't make sense until you look inside and see what they are trying to
do with it and how it controls the positioning of the cross-shaft.
Another thing that isn't obvious is that it has a locking mechanism (at >least in some models): if the knob is turned through 90 degrees, the
speed selector can't be moved. There is a line marked on the face of
the knob but it isn't at all obvious what it means. I assume this is to >prevent the motor being accidentally turned on by catching on the >reporter's sleeve when using it on the shoulder strap.
Now I have to ask: how and where did you learn all this stuff?
I'm very old, so I have had a long time to learn it.
You're
clearly an expert in this field whether you acknowledge it or not and
there are vanishingly few women who go down such a technical pathway,
certainly not in the 'old days' at any rate! Did you experience
discrimination on account of it? Must have been bloody difficult in an
all-male environment.
It's more complicated than that: I spent most of my life trying to act
like a man and only recently realised I had been a transwoman all
along. This meant that I didn't experience the same obstacles a woman >would have met but, instead, I was constantly bullied for not being
'manly' enough. Luckily my two parallel careers were in electronics and >biology, biology has always been open to women - and to men with a more >feminine outlook on life. Electronics was very mysogenistic to start
with but is becoming more woman-friendly now. My local radio club has >three husband-and-wife pairs of licenced radio amateurs. Most of the
other clubs in this area have at least one open transwoman and some have
a few others still "in the closet" - those statistics would be a good >research project for someone. This is a far cry from the early 1950s, >when Jean Walton had to change her name and persona to John Walton
before Decca would treat her/his electronics and mechanical design >abilities seriously.
I first worked in marine radio design but, when I left that, my main day >job became biology. I continued to have electronics as my hobby and
worked as a sub-contractor to the (UK) National Sound Archive in my >evenings and weekends.
Because I was running the sound recording job on a shoestring, I could
only afford to equip the 'studio' (a bench across the bay window in the >front room) with equipment that had been sold at scrap prices - but my
work had to meet full professional specification. This meant I had to >learn, very quickly, how to rebuild knackered bits of kit back to
factory specification and calibrate them to the satisfaction of my
N.S.A. boss, who was extremely helpful but a stickler for accuracy.
He was a BBC-trained studio manager and recording engineer from the days >when discs were the main medium and he had built his own recording
studio from scratch (with a home-made recording lathe). He acted as my >mentor and most of what I now know in the audio field can be traced back
to his teaching.
Nowadays the first question most people ask, when presented with a
problem, is "what can I buy that will do the job for me". I am still of >the old school that asks "What have I got that can be adapted to do the >job? ...and if I haven't got anything, can I make something?"
Well, as a right-of-center Libertarian I fully support your choice.
That may surprise you if all you know of people like myself is what
you hear about us on the BBC!
Anyway, enough of politics; a subject I try to
avoid discussing as much as possible!
Cursitor Doom <cd@notformail.com> wrote:
On Fri, 16 Jan 2026 10:21:16 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Cursitor Doom <cd@notformail.com> wrote:
On Thu, 15 Jan 2026 11:54:45 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
[...]
Just a minor point:
It doesn't look as though there will be room for the capacitor inside
the plug where it will be screened, so the capacitor needs to be at the >> >> >tip of the probe with the resistor between it and the cable end. This >> >> >is so that the resistor attenuates any stray signals picked up by the
capacitor. If the capacitor were on the amplifier side of the resistor, >> >> >anything it picked up from the mains or the proximity of your hand,
acting like an aerial, would be fully amplified.
A fine but important point there! We often think 'stuff in series' can
go in any order, but so often there are exceptions due to unexpected
effects which must be allowed for. I do have some more suitable
sub-min 10n caps which would be much easier to shield. I'll use those
on the Mk II version. :-)
Make sure it has a high enough voltage rating if you ever want to
fault-find valve equipment.
[...]
I also made another discovery about the possible cause of the varying >> >> >> speed. It turns out that if the machine isn't placed in one of the
neutral positions on the speed selector dial when stored, then the
rubber belt around the drive wheel will be under pressure from the
pinion it butts up against, causing a flat spot. Bizarrely, there's NO >> >> >> mention of this in the owner's handbook! It does say that the machine >> >> >> should not be left unattended for long periods switched off with the >> >> >> 'play' key left depressed, but that's pretty much common sense. I only >> >> >> became aware of the importance of the neutral switch position from
reading some guy's comment he'd left under a Youtube video of someone >> >> >> demonstrating this deck. Consequently, I'd been leaving the machine in >> >> >> this state when unused and I would put money that previous owners have >> >> >> done the same thing during their ownership too. So there may well be >> >> >> multiple depressions on that belt as a result. I'll check on Sunday
when I next get the lid off. Hopefully if the material's reslient
enough, it may recover in time.....
Tht is very important and will account for 'hiccupy' speed veriations. >> >> >I seem to remember my Uhers needed to be put into the 'neutral' position >> >> >to switch off the motor, so the user was unlikely to forget, as they
were acutely aware of the need to conserve battery power on location.
If yours has only been used on a mains adaptor, I can see how the
misunderstanding could have occurred.
There's no give away 'feel' to it like when you release the 'play' key
you can sense the tension coming off. That doesn't happen with that
knob at all.
The speed selector is a very counter-intuitive thing to operste, it
doesn't make sense until you look inside and see what they are trying to
do with it and how it controls the positioning of the cross-shaft.
Another thing that isn't obvious is that it has a locking mechanism (at
least in some models): if the knob is turned through 90 degrees, the
speed selector can't be moved. There is a line marked on the face of
the knob but it isn't at all obvious what it means. I assume this is to
prevent the motor being accidentally turned on by catching on the
reporter's sleeve when using it on the shoulder strap.
Now I have to ask: how and where did you learn all this stuff?
I'm very old, so I have had a long time to learn it.
You're
clearly an expert in this field whether you acknowledge it or not and
there are vanishingly few women who go down such a technical pathway,
certainly not in the 'old days' at any rate! Did you experience
discrimination on account of it? Must have been bloody difficult in an
all-male environment.
It's more complicated than that: I spent most of my life trying to act
like a man and only recently realised I had been a transwoman all
along. This meant that I didn't experience the same obstacles a woman
would have met but, instead, I was constantly bullied for not being
'manly' enough. Luckily my two parallel careers were in electronics and
biology, biology has always been open to women - and to men with a more
feminine outlook on life. Electronics was very mysogenistic to start
with but is becoming more woman-friendly now. My local radio club has
three husband-and-wife pairs of licenced radio amateurs. Most of the
other clubs in this area have at least one open transwoman and some have
a few others still "in the closet" - those statistics would be a good
research project for someone. This is a far cry from the early 1950s,
when Jean Walton had to change her name and persona to John Walton
before Decca would treat her/his electronics and mechanical design
abilities seriously.
I first worked in marine radio design but, when I left that, my main day
job became biology. I continued to have electronics as my hobby and
worked as a sub-contractor to the (UK) National Sound Archive in my
evenings and weekends.
Because I was running the sound recording job on a shoestring, I could
only afford to equip the 'studio' (a bench across the bay window in the
front room) with equipment that had been sold at scrap prices - but my
work had to meet full professional specification. This meant I had to
learn, very quickly, how to rebuild knackered bits of kit back to
factory specification and calibrate them to the satisfaction of my
N.S.A. boss, who was extremely helpful but a stickler for accuracy.
He was a BBC-trained studio manager and recording engineer from the days
when discs were the main medium and he had built his own recording
studio from scratch (with a home-made recording lathe). He acted as my
mentor and most of what I now know in the audio field can be traced back
to his teaching.
Nowadays the first question most people ask, when presented with a
problem, is "what can I buy that will do the job for me". I am still of
the old school that asks "What have I got that can be adapted to do the
job? ...and if I haven't got anything, can I make something?"
Well, as a right-of-center Libertarian I fully support your choice.
Being transgender isn't a choice - the only choice I have is what I do
about it. Do I go around feeling permanently ill at ease with myself
and hating what I have to do in order to fulfil society's expectations
or do I say "Sod it! That's their problem if they can't cope with me
being me"? I don't set out to create situations where people are upset
- but I won't let them impose their prejudices on me. That is one of
the benefits of growing old (mandatory) and cantankerous (optional).
That may surprise you if all you know of people like myself is what
you hear about us on the BBC!
The BBC has an agenda on many topics; having heard their coverage of
things I happen to know about, I no longer trust anything they say. At
best a lot of their journalism is sloppy and they just repeat propaganda >because its easier than searching out the truth - at worst they
knowingly repeat blatant lies that happen to suit their preconceived
agenda.
[...]
Anyway, enough of politics; a subject I try to
avoid discussing as much as possible!
Back to tape recorders then....
| Sysop: | Jacob Catayoc |
|---|---|
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