On Wed, 3/11/2026 8:02 PM, JR Dolobson wrote:
I have an old Dell XPS 420 desktop that wouldn't come on some weeks ago. ÿI was finally able to get it working by cutting the green wire connecting the power supply to motherboard and then using a switch to ground the green wire (on the power supply side) to ground and then pressing the front power button on the desktop.
Five days ago, even the switch workaround failed and the unit failed to come on.
First thing I did was remove all the cards within (video card, USB 3 card, etc).ÿ Still no power up.ÿ I then decided to unplug the large 24 pin connector from power supply to motherboard and, when I grounded the power supply green wire, the power supply came on and I believe all the SSD drives did too as I didn't disconnect those.ÿ I decided to try opening the front DVD drive and it opened right up electronically.ÿ So, the power supply was now working as long as the 24 pin connector was unplugged from the motherboard.
I'm not sure, but it seems to me like there is a short on the motherboard somewhere, since the power supply won't start when the 24 pin connector is plugged in.
Tonight, after plugging back in the 24 pin connector, I decided to keep flipping the external toggle switch to ground while noting whether or not the power supply would start and the blue light would illuminate. Much to my surprise, it finally did, I depressed the front blue illuminated power button and the PC booted up.ÿ In fact, I am sending this message from it now.
Now I'm not sure whether I want to turn it off again for fear I'll be back to no power up.ÿ Any idea what could be causing what appears to be an intermittent no power up issue?ÿ Can we rule out the power supply since it seems to activate if not plugging in the 24 pin connector (but it is now)?
Any ideas would be welcome.ÿ This old 2008 desktop is my workhorse and I am basically lost without it.ÿ My PC and Internet demands are light, so that's why I am still able to use it.ÿ There are a lot of electrolytics on the motherboard and I understand that those fail with age and can cause a short.ÿ I do have an electrolytic tester, but I'd have to remove the motherboard to access the caps and it won't be easy.ÿ If that's even what could be wrong.
Thanks in advance for any help.
At this point, it is replace ATX PSU.
Chipset is X38. CPU is Core2 Quad, LGA775.
CPU is missing POPCNT instruction in SSE4 and
so is not a good candidate for a Windows 11 attempt
with Rufus. RAM is DDR2 presumably, but there were also
DDR3 versions (the Q45 had DDR3 and it allowed up to
4x4GB DDR3.
PSU might well have regular ATX pinout. You can compare the
colours, to a formfactors.org document and the order of colors
on the 24 pin should be the same. If you're lazy, a PSU at
Best Buy would be on the order of $150 (as they only stock
"mid-range" components, like $600 video cards and $150 supplies).
Try to get an 80+ supply - the Dell 420 is a BTX, and the airflow
in the Dell designs is "shockingly low". It doesn't turn the
fan up enough under load.
Also, in checking my Optiplex 780 refurb, I notice my BTX setup,
the mounting screws for the PSU are flipped 180 degrees for BTX.
If you stick a new ATX supply in there, the hole pattern will
make the new PSU intake vent face the top of the
computer case ("blocked"). Versus sucking in air from inside the case,
while the intake points downward (on a BTX PSU). Keep that
visualization in mind when shopping for a PSU. Some computer
cases are quite dependent on the four rear screws, for adequate
mechanical support for the PSU weight. The screws have custom
offsets, enforcing a single orientation.
*******
As there is a component shortage ongoing, refurbs should rise in
price as new computers rise in price. Normally, some of the
quad core refurbs would be champs right now, but the price
will tell you what kind of "demand" exists. I really don't
think all the scalpers will buy up the refurbs, but ordinary
users might partake.
BTX was a jolly mistake of an idea. I've got one, and enjoy all
the silly highlights of the thing. Like a potted plant, you could attempt
to move the motherboard to another case but... who are we fooling.
That never works. You'd have to make a custom case out of 2x4's
and saw out the bits that don't match :-) It's possible even
an open ATX lab bench would not have dual ATX/BTX capability.
BTX has been out of production for a while, so after market
conveniences might not be there for you.
Nothing says you cannot mount a PSU outside the case and
run the cables inside. But this will take a PSU with
longer cabling, to reach everything in the Dell. For example,
Fortron/Sparkle puts "precise/short" cables on their PSUs
and would only be a candidate for a ATX computer case, with
all load connectors being "conveniently placed" for the PSU to work.
A few ATX PSU manufacturers, make a block diagram of their
supply, with the length of the cables marked in the diagram.
This is handy for jobs where you know the reach will be longer.
My largest computer case, has the ATX PSU in the bottom of the case.
If instead I had to mount that outside the case, the wires might not be
long enough. The machine also has an "open top", which is "death for modders",
no place to screw down a bodge up there.
You could attempt to buy a Dell PSU, but what shape would one
of those be in ? The PCPC company used to make "Dell Lookalikes",
and then those could be newer designs. PCPC was bought up or something.
Firepower (still in business... maybe) - research this
https://en.wikipedia.org/wiki/PC_Power_and_Cooling
Paul
On 3/11/26 11:55 PM, Paul wrote:
On Wed, 3/11/2026 8:02 PM, JR Dolobson wrote:
I have an old Dell XPS 420 desktop that wouldn't come on some weeks
ago. ÿI was finally able to get it working by cutting the green wire
connecting the power supply to motherboard and then using a switch to
ground the green wire (on the power supply side) to ground and then
pressing the front power button on the desktop.
Five days ago, even the switch workaround failed and the unit failed
to come on.
First thing I did was remove all the cards within (video card, USB 3
card, etc).ÿ Still no power up.ÿ I then decided to unplug the large
24 pin connector from power supply to motherboard and, when I
grounded the power supply green wire, the power supply came on and I
believe all the SSD drives did too as I didn't disconnect those.ÿ I
decided to try opening the front DVD drive and it opened right up
electronically.ÿ So, the power supply was now working as long as the
24 pin connector was unplugged from the motherboard.
I'm not sure, but it seems to me like there is a short on the
motherboard somewhere, since the power supply won't start when the 24
pin connector is plugged in.
Tonight, after plugging back in the 24 pin connector, I decided to
keep flipping the external toggle switch to ground while noting
whether or not the power supply would start and the blue light would
illuminate. Much to my surprise, it finally did, I depressed the
front blue illuminated power button and the PC booted up.ÿ In fact, I
am sending this message from it now.
Now I'm not sure whether I want to turn it off again for fear I'll be
back to no power up.ÿ Any idea what could be causing what appears to
be an intermittent no power up issue?ÿ Can we rule out the power
supply since it seems to activate if not plugging in the 24 pin
connector (but it is now)?
Any ideas would be welcome.ÿ This old 2008 desktop is my workhorse
and I am basically lost without it.ÿ My PC and Internet demands are
light, so that's why I am still able to use it.ÿ There are a lot of
electrolytics on the motherboard and I understand that those fail
with age and can cause a short.ÿ I do have an electrolytic tester,
but I'd have to remove the motherboard to access the caps and it
won't be easy.ÿ If that's even what could be wrong.
Thanks in advance for any help.
At this point, it is replace ATX PSU.
Chipset is X38. CPU is Core2 Quad, LGA775.
CPU is missing POPCNT instruction in SSE4 and
so is not a good candidate for a Windows 11 attempt
with Rufus. RAM is DDR2 presumably, but there were also
DDR3 versions (the Q45 had DDR3 and it allowed up to
4x4GB DDR3.
PSU might well have regular ATX pinout. You can compare the
colours, to a formfactors.org document and the order of colors
on the 24 pin should be the same. If you're lazy, a PSU at
Best Buy would be on the order of $150 (as they only stock
"mid-range" components, like $600 video cards and $150 supplies).
Try to get an 80+ supply - the Dell 420 is a BTX, and the airflow
in the Dell designs is "shockingly low". It doesn't turn the
fan up enough under load.
Also, in checking my Optiplex 780 refurb, I notice my BTX setup,
the mounting screws for the PSU are flipped 180 degrees for BTX.
If you stick a new ATX supply in there, the hole pattern will
make the new PSU intake vent face the top of the
computer case ("blocked"). Versus sucking in air from inside the case,
while the intake points downward (on a BTX PSU). Keep that
visualization in mind when shopping for a PSU. Some computer
cases are quite dependent on the four rear screws, for adequate
mechanical support for the PSU weight. The screws have custom
offsets, enforcing a single orientation.
*******
As there is a component shortage ongoing, refurbs should rise in
price as new computers rise in price. Normally, some of the
quad core refurbs would be champs right now, but the price
will tell you what kind of "demand" exists. I really don't
think all the scalpers will buy up the refurbs, but ordinary
users might partake.
BTX was a jolly mistake of an idea. I've got one, and enjoy all
the silly highlights of the thing. Like a potted plant, you could attempt
to move the motherboard to another case but... who are we fooling.
That never works. You'd have to make a custom case out of 2x4's
and saw out the bits that don't match :-) It's possible even
an open ATX lab bench would not have dual ATX/BTX capability.
BTX has been out of production for a while, so after market
conveniences might not be there for you.
Nothing says you cannot mount a PSU outside the case and
run the cables inside. But this will take a PSU with
longer cabling, to reach everything in the Dell. For example,
Fortron/Sparkle puts "precise/short" cables on their PSUs
and would only be a candidate for a ATX computer case, with
all load connectors being "conveniently placed" for the PSU to work.
A few ATX PSU manufacturers, make a block diagram of their
supply, with the length of the cables marked in the diagram.
This is handy for jobs where you know the reach will be longer.
My largest computer case, has the ATX PSU in the bottom of the case.
If instead I had to mount that outside the case, the wires might not be
long enough. The machine also has an "open top", which is "death for
modders",
no place to screw down a bodge up there.
You could attempt to buy a Dell PSU, but what shape would one
of those be in ? The PCPC company used to make "Dell Lookalikes",
and then those could be newer designs. PCPC was bought up or something.
ÿÿÿ Firepower (still in business... maybe) - research this
ÿÿÿ https://en.wikipedia.org/wiki/PC_Power_and_Cooling
ÿÿ Paul
I found an unused Ultra ult-vx700 I had in storage yesterday.ÿ Problem
with it was that I cut about half the 24 pin wires away because I had
tried using the PSU for another purpose.ÿ However, a lot of tedious soldering and heat shrinking, and I have spliced on an unused 24 pin connector from yet another unused (and burned out) PSU today.ÿ I was extremely careful to match the original connector with the new (spliced) one.ÿ Taking a break now, then will try it in the PC.
My only concern was the unused pin on Dell's 24 pin connector (pin 20)
yet there was a wire there, so at least wired, in the VX700's original connector. I decided not to use that wire and leave pin 20 unused.ÿ Not
sure that will be an issue.ÿ I wasn't able to find any voltage data for
the VX700's connector other than the PSU is ATX design.
Since the '700 is what I think they call "modular" in design, there are about a dozen (or more) connectors included that terminate in the
various connectors needed for the Dell.ÿ These are all plugged in to
sockets on one side of the PSU.
I hope for success.ÿ Not going to install it yet, just try it out from outside the case.
On 3/13/26 5:31 AM, JR Dolobson wrote:
On 3/11/26 11:55 PM, Paul wrote:
On Wed, 3/11/2026 8:02 PM, JR Dolobson wrote:
I have an old Dell XPS 420 desktop that wouldn't come on some weeks
ago. ÿI was finally able to get it working by cutting the green wire
connecting the power supply to motherboard and then using a switch
to ground the green wire (on the power supply side) to ground and
then pressing the front power button on the desktop.
Five days ago, even the switch workaround failed and the unit failed
to come on.
First thing I did was remove all the cards within (video card, USB 3
card, etc).ÿ Still no power up.ÿ I then decided to unplug the large
24 pin connector from power supply to motherboard and, when I
grounded the power supply green wire, the power supply came on and I
believe all the SSD drives did too as I didn't disconnect those.ÿ I
decided to try opening the front DVD drive and it opened right up
electronically.ÿ So, the power supply was now working as long as the
24 pin connector was unplugged from the motherboard.
I'm not sure, but it seems to me like there is a short on the
motherboard somewhere, since the power supply won't start when the
24 pin connector is plugged in.
Tonight, after plugging back in the 24 pin connector, I decided to
keep flipping the external toggle switch to ground while noting
whether or not the power supply would start and the blue light would
illuminate. Much to my surprise, it finally did, I depressed the
front blue illuminated power button and the PC booted up.ÿ In fact,
I am sending this message from it now.
Now I'm not sure whether I want to turn it off again for fear I'll
be back to no power up.ÿ Any idea what could be causing what appears
to be an intermittent no power up issue?ÿ Can we rule out the power
supply since it seems to activate if not plugging in the 24 pin
connector (but it is now)?
Any ideas would be welcome.ÿ This old 2008 desktop is my workhorse
and I am basically lost without it.ÿ My PC and Internet demands are
light, so that's why I am still able to use it.ÿ There are a lot of
electrolytics on the motherboard and I understand that those fail
with age and can cause a short.ÿ I do have an electrolytic tester,
but I'd have to remove the motherboard to access the caps and it
won't be easy.ÿ If that's even what could be wrong.
Thanks in advance for any help.
At this point, it is replace ATX PSU.
Chipset is X38. CPU is Core2 Quad, LGA775.
CPU is missing POPCNT instruction in SSE4 and
so is not a good candidate for a Windows 11 attempt
with Rufus. RAM is DDR2 presumably, but there were also
DDR3 versions (the Q45 had DDR3 and it allowed up to
4x4GB DDR3.
PSU might well have regular ATX pinout. You can compare the
colours, to a formfactors.org document and the order of colors
on the 24 pin should be the same. If you're lazy, a PSU at
Best Buy would be on the order of $150 (as they only stock
"mid-range" components, like $600 video cards and $150 supplies).
Try to get an 80+ supply - the Dell 420 is a BTX, and the airflow
in the Dell designs is "shockingly low". It doesn't turn the
fan up enough under load.
Also, in checking my Optiplex 780 refurb, I notice my BTX setup,
the mounting screws for the PSU are flipped 180 degrees for BTX.
If you stick a new ATX supply in there, the hole pattern will
make the new PSU intake vent face the top of the
computer case ("blocked"). Versus sucking in air from inside the case,
while the intake points downward (on a BTX PSU). Keep that
visualization in mind when shopping for a PSU. Some computer
cases are quite dependent on the four rear screws, for adequate
mechanical support for the PSU weight. The screws have custom
offsets, enforcing a single orientation.
*******
As there is a component shortage ongoing, refurbs should rise in
price as new computers rise in price. Normally, some of the
quad core refurbs would be champs right now, but the price
will tell you what kind of "demand" exists. I really don't
think all the scalpers will buy up the refurbs, but ordinary
users might partake.
BTX was a jolly mistake of an idea. I've got one, and enjoy all
the silly highlights of the thing. Like a potted plant, you could
attempt
to move the motherboard to another case but... who are we fooling.
That never works. You'd have to make a custom case out of 2x4's
and saw out the bits that don't match :-) It's possible even
an open ATX lab bench would not have dual ATX/BTX capability.
BTX has been out of production for a while, so after market
conveniences might not be there for you.
Nothing says you cannot mount a PSU outside the case and
run the cables inside. But this will take a PSU with
longer cabling, to reach everything in the Dell. For example,
Fortron/Sparkle puts "precise/short" cables on their PSUs
and would only be a candidate for a ATX computer case, with
all load connectors being "conveniently placed" for the PSU to work.
A few ATX PSU manufacturers, make a block diagram of their
supply, with the length of the cables marked in the diagram.
This is handy for jobs where you know the reach will be longer.
My largest computer case, has the ATX PSU in the bottom of the case.
If instead I had to mount that outside the case, the wires might not be
long enough. The machine also has an "open top", which is "death for
modders",
no place to screw down a bodge up there.
You could attempt to buy a Dell PSU, but what shape would one
of those be in ? The PCPC company used to make "Dell Lookalikes",
and then those could be newer designs. PCPC was bought up or something.
ÿÿÿ Firepower (still in business... maybe) - research this
ÿÿÿ https://en.wikipedia.org/wiki/PC_Power_and_Cooling
ÿÿ Paul
I found an unused Ultra ult-vx700 I had in storage yesterday.ÿ Problem
with it was that I cut about half the 24 pin wires away because I had
tried using the PSU for another purpose.ÿ However, a lot of tedious
soldering and heat shrinking, and I have spliced on an unused 24 pin
connector from yet another unused (and burned out) PSU today.ÿ I was
extremely careful to match the original connector with the new
(spliced) one.ÿ Taking a break now, then will try it in the PC.
My only concern was the unused pin on Dell's 24 pin connector (pin 20)
yet there was a wire there, so at least wired, in the VX700's original
connector. I decided not to use that wire and leave pin 20 unused.
Not sure that will be an issue.ÿ I wasn't able to find any voltage
data for the VX700's connector other than the PSU is ATX design.
Since the '700 is what I think they call "modular" in design, there
are about a dozen (or more) connectors included that terminate in the
various connectors needed for the Dell.ÿ These are all plugged in to
sockets on one side of the PSU.
I hope for success.ÿ Not going to install it yet, just try it out from
outside the case.
Working, normal boot up now, no extra switches or tricks!ÿ I guess is
was the PSU.ÿ There is only one problem.... I was unable to find a 6 pin video card cable!ÿ Since the old PSU had one, and it worked without
plugging in the 24 pin connector, I actually have it running
simultaneously with the '700 and just powering the video card with it.
Obviously, I can't keep it this way so.... can you or anyone suggest a 4
pin to 6 pin adapter.ÿ I'd rather hack up one of these unused 4 pin connectors and create a 4 pin to 6 pin plug if possible....
Done! Made a DIY adapter after finding plug data online. All working
fine now. After weeks, the PC is booting up again normally with no
extra switch. I don't believe this PSU quite matches the specs you mentioned before, but I believe it was originally for "elementary" gamer systems.
I'll keep it on top of the case for a week or so just to make sure all
is well, then pull the existing one and replace it with this one after taking note of the ventalation as you mentioned prior.
I honestly didn't think the PSU was to blame. You did mention it weeks
back after I had to start using the external switch to get boot up.
The original PSU is still working as long as I don't plug in the 24 pin connector to motherboard.
At some point, I'll have to open it and see
if there is a bad electrolytic or two. I have a tester for
electrolytics in circuit, but hasn't been used since purchase a couple
of years back. Will be a good test for it.
Thanks again for all the help, both you, Paul, and the others.
On 2026/3/13 11:52:40, JR Dolobson wrote:
[]
Done! Made a DIY adapter after finding plug data online. All working
fine now. After weeks, the PC is booting up again normally with no
extra switch. I don't believe this PSU quite matches the specs you
mentioned before, but I believe it was originally for "elementary" gamer
systems.
Glad to hear all is well.
I'll keep it on top of the case for a week or so just to make sure all
is well, then pull the existing one and replace it with this one after
taking note of the ventalation as you mentioned prior.
I honestly didn't think the PSU was to blame. You did mention it weeks
back after I had to start using the external switch to get boot up.
The original PSU is still working as long as I don't plug in the 24 pin
connector to motherboard.
That has elements of "apart from that, Mrs. Lincoln, did you enjoy the
play?"
On 2026/3/13 11:52:40, JR Dolobson wrote:
[]
Done! Made a DIY adapter after finding plug data online. All working
fine now. After weeks, the PC is booting up again normally with no
extra switch. I don't believe this PSU quite matches the specs you
mentioned before, but I believe it was originally for "elementary" gamer
systems.
Glad to hear all is well.
I'll keep it on top of the case for a week or so just to make sure all
is well, then pull the existing one and replace it with this one after
taking note of the ventalation as you mentioned prior.
I honestly didn't think the PSU was to blame. You did mention it weeks
back after I had to start using the external switch to get boot up.
The original PSU is still working as long as I don't plug in the 24 pin
connector to motherboard.
That has elements of "apart from that, Mrs. Lincoln, did you enjoy the
play?"
At some point, I'll have to open it and see
Be careful; as well as the high voltages (even after off for a while, in theory), a few decades ago I cut myself; I think the normal insides of a
PC they're reasonably careful as people might be expected to poke around inside, but the insides of a power supply they seemed to think fewer
people would go, and were more careless about designing how the parts of
its case go together. At least, that's what I assumed. Things may have improved.
if there is a bad electrolytic or two. I have a tester for
electrolytics in circuit, but hasn't been used since purchase a couple
of years back. Will be a good test for it.
Sounds like a useful toy!
YW.
Thanks again for all the help, both you, Paul, and the others.
Partially defunct Dell PSU removed from casing within the last hour and replaced with the Ultra ult-vx700.
Dell PSU removal was not easy.ÿ There is an extra long bunch of wires
that wrap around the motherboard, go underneath the air shroud, and terminate in various connectors.ÿ So, it wasn't as simple as just the 24
pin connector and 4 pin CPU connector.ÿ Others with a similar
predicament either removed the air shroud (which also apparently
separates the CPU heatsink, something I did not want to do), or cut the group of wires near the PSU.ÿ Since I hope to maybe resurrect the PSU at some point and not have to solder a zillion splices and heat shrink them again, I worked the connector end back and forth until it finally pulled through.ÿ So, Dell PSU removal is totally intact.
Ultra installation went ok.ÿ Not a perfect fit, from an attachment to
casing perspective, as I was only able to attach using two out of the
four screws.ÿ I believe this PSU has two fans, one at the front and
another at the rear, but of course not certain of this.ÿ That's the way
the ventilation will have to do.ÿ There are some small side vents, but they'll be right up against the sides of the desktop casing once closed.
ÿHope that is not an issue.ÿ The original Dell PSU did not even have
the side vents only front and rear, so I think all will be ok.
Dell uses some small unknown screws to keep the PSU assembled.ÿ Anyone
know what they are?ÿ Definitely not phillips heads, maybe some sort of
star heads.
On 15/03/2026 4:03 am, JR Dolobson wrote:
On 3/13/26 10:39 AM, J. P. Gilliver wrote:
On 2026/3/13 11:52:40, JR Dolobson wrote:
[]
Done!ÿ Made a DIY adapter after finding plug data online.ÿ All working >>>> fine now.ÿ After weeks, the PC is booting up again normally with no
extra switch.ÿ I don't believe this PSU quite matches the specs you
mentioned before, but I believe it was originally for "elementary"
gamer
systems.
Glad to hear all is well.
I'll keep it on top of the case for a week or so just to make sure all >>>> is well, then pull the existing one and replace it with this one after >>>> taking note of the ventalation as you mentioned prior.
I honestly didn't think the PSU was to blame.ÿ You did mention it weeks >>>> back after I had to start using the external switch to get boot up.
The original PSU is still working as long as I don't plug in the 24 pin >>>> connector to motherboard.
That has elements of "apart from that, Mrs. Lincoln, did you enjoy the
play?"
At some point, I'll have to open it and see
Be careful; as well as the high voltages (even after off for a while, in >>> theory), a few decades ago I cut myself; I think the normal insides of a >>> PC they're reasonably careful as people might be expected to poke around >>> inside, but the insides of a power supply they seemed to think fewer
people would go, and were more careless about designing how the parts of >>> its case go together. At least, that's what I assumed. Things may have
improved.
One time, I was "hit" with an unexpected charge from a camera flash
that had been disassembled.ÿ The electrolytic obviously wasn't
discharged before I touched it.ÿ Sent me about halfway across the
room.ÿ I know PC and indeed other power supplies can harbor nasty
charges long after deactivation.
I can remember, back in about 1980, I was working on a 20kW PEP,
Automatic Tune H.F. Radio Transmitter (with 7.500 Volt H.T.) that wasn't auto-tuning correctly. I wanted to make an adjustment in the high power
RF cabinet so I switched off the HT. I then switched off the LT. I
walked around the back of the 3mtr by 1mtr cabinet and slide open the panelling there and climbed a three or four step ladder then removed the internal cabinet cover. When I removed that cover, a knife-switch was SUPPOSED to short the 7500 or 8000 HT Filter Capacitors to Deck
Are you getting the idea that I wasn't rushing to get at the problem
area?? So the H.T. should have drained away.
Anyway, after removing the cover and (supposedly) shorting the HT rail
to deck, I reached in with my left hand...... and WAAAACCCCKKKK!
My mind told me my Right Hand had reached in and lifted my left arm off
some unknown Voltage point.
The problem with that is that, a couple of years before hand, I was
involved in a Road Accident .... which resulted in my Right Arm being amputated above the elbow ..... so I had NO Right Hand .... BUT MY MIND
TOLD ME MY RIGHT HAND HAD REACHED IN AND LIFTED MY LEFT HAND.
I still have a spot on the inside of my Left Forearm indicating where I
was zapped. I'm guessing the 7500 or 8000 HT might have been developed across two capacitors in series and the knife-switch ONLY shorted the
top point to deck .... and I might have contacted the mid-point .... or something like that!!
Marked for life!! ;-P
When I decide to open up the partially defunct Dell PSU, I'll also proceed slowly.ÿ
Although my ESR tester can discharge caps, it can only do so up to a certain point,
so I'll take the extra step and manually discharge the electrolytics first.
On 15/03/2026 4:03 am, JR Dolobson wrote:
On 3/13/26 10:39 AM, J. P. Gilliver wrote:
On 2026/3/13 11:52:40, JR Dolobson wrote:
[]
Done!ÿ Made a DIY adapter after finding plug data online.ÿ All working >>>> fine now.ÿ After weeks, the PC is booting up again normally with no
extra switch.ÿ I don't believe this PSU quite matches the specs you
mentioned before, but I believe it was originally for "elementary" gamer >>>> systems.
Glad to hear all is well.
I'll keep it on top of the case for a week or so just to make sure all >>>> is well, then pull the existing one and replace it with this one after >>>> taking note of the ventalation as you mentioned prior.
I honestly didn't think the PSU was to blame.ÿ You did mention it weeks >>>> back after I had to start using the external switch to get boot up.
The original PSU is still working as long as I don't plug in the 24 pin >>>> connector to motherboard.
That has elements of "apart from that, Mrs. Lincoln, did you enjoy the
play?"
At some point, I'll have to open it and see
Be careful; as well as the high voltages (even after off for a while, in >>> theory), a few decades ago I cut myself; I think the normal insides of a >>> PC they're reasonably careful as people might be expected to poke around >>> inside, but the insides of a power supply they seemed to think fewer
people would go, and were more careless about designing how the parts of >>> its case go together. At least, that's what I assumed. Things may have
improved.
One time, I was "hit" with an unexpected charge from a camera flash that had been disassembled.ÿ The electrolytic obviously wasn't discharged before I touched it.ÿ Sent me about halfway across the room.ÿ I know PC and indeed other power supplies can harbor nasty charges long after deactivation.
I can remember, back in about 1980, I was working on a 20kW PEP, Automatic Tune H.F. Radio Transmitter (with 7.500 Volt H.T.) that wasn't auto-tuning correctly. I wanted to make an adjustment in the high power RF cabinet so I switched off the HT. I then switched off the LT. I walked around the back of the 3mtr by 1mtr cabinet and slide open the panelling there and climbed a three or four step ladder then removed the internal cabinet cover. When I removed that cover, a knife-switch was SUPPOSED to short the 7500 or 8000 HT Filter Capacitors to Deck
Are you getting the idea that I wasn't rushing to get at the problem area?? So the H.T. should have drained away.
Anyway, after removing the cover and (supposedly) shorting the HT rail to deck, I reached in with my left hand...... and WAAAACCCCKKKK!
My mind told me my Right Hand had reached in and lifted my left arm off some unknown Voltage point.
The problem with that is that, a couple of years before hand, I was involved in a Road Accident .... which resulted in my Right Arm being amputated above the elbow ..... so I had NO Right Hand .... BUT MY MIND TOLD ME MY RIGHT HAND HAD REACHED IN AND LIFTED MY LEFT HAND.
I still have a spot on the inside of my Left Forearm indicating where I was zapped. I'm guessing the 7500 or 8000 HT might have been developed across two capacitors in series and the knife-switch ONLY shorted the top point to deck .... and I might have contacted the mid-point .... or something like that!!
Marked for life!! ;-P
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