What a bonehead!!! (repairing P PC PS)

[Impmon]

I had a power supply from PC that recently started giving intermitty problem
with random shutdown and restarts. Upon opening the power supply, I found
(surprise, surprise) 3 caps that was ballooned up. 1 of them was rated 10v
but it was connected to -12v rail. What kind of moron uses a 10v caps on a
12v rail??? (the other rated at 10v was on +5v and 16v on +12v rail) I
think the fact 2 large 1w resistors were next to that 3 caps caused its
failure.

The obvious question, is it worth replacing those (and maybe other caps) to
salvage a 400 watts power supply or would there be something else that could
go wrong? The caps were right at the spot where the wires connected to the
board and leads to PC so I'm thinking they are simply filter cap for
maintaining voltage level.

 

[Bill Bolle]

I had a power supply from PC that recently started giving intermitty problem
with random shutdown and restarts. Upon opening the power supply, I found
(surprise, surprise) 3 caps that was ballooned up. 1 of them was rated 10v
but it was connected to -12v rail. What kind of moron uses a 10v caps on a
12v rail??? (the other rated at 10v was on +5v and 16v on +12v rail) I
think the fact 2 large 1w resistors were next to that 3 caps caused its
failure.

The obvious question, is it worth replacing those (and maybe other caps) to
salvage a 400 watts power supply or would there be something else that could
go wrong? The caps were right at the spot where the wires connected to the
board and leads to PC so I'm thinking they are simply filter cap for
maintaining voltage level.

A 400 watt power supply is worth about 50 bucks and three caps at
Radio Shack is about 3 bucks. If the supply is still faulty after
changing the caps you can figure that you got 3 bucks worth of
education as to what the problem wasn't.
Bill

 

[Jerry G.]

If the machine has a good value to you, I would think to replace the
complete supply for reliability reasons. You may change the caps, but the
rest of the supply is old.

--

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Jerry Greenberg GLG Technologies GLG
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I had a power supply from PC that recently started giving intermitty problem
with random shutdown and restarts. Upon opening the power supply, I found
(surprise, surprise) 3 caps that was ballooned up. 1 of them was rated 10v
but it was connected to -12v rail. What kind of moron uses a 10v caps on a
12v rail??? (the other rated at 10v was on +5v and 16v on +12v rail) I
think the fact 2 large 1w resistors were next to that 3 caps caused its
failure.

The obvious question, is it worth replacing those (and maybe other caps) to
salvage a 400 watts power supply or would there be something else that could
go wrong? The caps were right at the spot where the wires connected to the
board and leads to PC so I'm thinking they are simply filter cap for
maintaining voltage level.

 

[James Sweet]

I had a power supply from PC that recently started giving intermitty problem
with random shutdown and restarts. Upon opening the power supply, I found
(surprise, surprise) 3 caps that was ballooned up. 1 of them was rated 10v
but it was connected to -12v rail. What kind of moron uses a 10v caps on a
12v rail??? (the other rated at 10v was on +5v and 16v on +12v rail) I
think the fact 2 large 1w resistors were next to that 3 caps caused its
failure.

The obvious question, is it worth replacing those (and maybe other caps) to
salvage a 400 watts power supply or would there be something else that could
go wrong? The caps were right at the spot where the wires connected to the
board and leads to PC so I'm thinking they are simply filter cap for
maintaining voltage level.

The wrong cap probably got stuck in there by accident, it's all done by
machine.

I would certainly replace the caps, that's probably the only problem,
replace all the output ones if you can, they're cheap and the others will
likely fail. If you use good quality capacitors and touch up any bad
soldering your power supply will probably last almost forever, that's about
all I ever see fail on those.

 

[do_not_spam_me]

I had a power supply from PC that recently started giving
intermitty problem with random shutdown and restarts. Upon
opening the power supply, I found (surprise, surprise) 3 caps
that was ballooned up. 1 of them was rated 10v but it was
connected to -12v rail. What kind of moron uses a 10v caps
on a 12v rail???

The kind who assumes he can get buy with it because capacitors can
withstand twice their rated voltage? I had a supply with 16V
capacitors that were fed 50V spikes.

is it worth replacing those (and maybe other caps) to salvage
a 400 watts power supply or would there be something else that
could go wrong?

It depends on how cheaply you can get good replacement caps (made for
high frequency, not just 105 Celcius) and how good the power supply
is. I've seen top-quality 300-350W power supplies for less than $30,
like some of these, www.pricewatch.com/2/297/2399-1.htm (Newegg.com
and Directron.com sell Fortron/Sparkle/Hi-Q very cheaply), and they
outperform many supplies rated 50-100W higher.

Replacing the caps is probably going to fix everything, but I'd toss
the supply or use it for spare parts if it's a junk mystery brand or
any of the numerous Deer brands (Austin, Allied, Codegen, L&C, Logic,
Turbolink, Powerstar, Mercury, Duro, and many animal-related names:
Foxconn, Foxlink, Eagle, Hyena, Mustang). Even the Leadman brands
(Powmax, Raidmax, Robanton), which are probably the highest quality
junk, may not be worth any time or money. But some brands not common
in the retail market are actually very good, like Newton, NMB,
Lite-On, Zippy-Emacs, Delta (Acer), Astec, HEC (Heroichi, Compucase,
older Antec), and Channel Well (at least their A and B suffix models,
also newer Antec)

 

[Vector Viper]

I have seen caps in some Emerson 9" tv/vcr units put in backwards; in the
vertical section...
...IT happens....

 

[Impmon]

A 400 watt power supply is worth about 50 bucks and three caps at

Radio Shack is about 3 bucks. If the supply is still faulty after
changing the caps you can figure that you got 3 bucks worth of
education as to what the problem wasn't.

I've checked Radio Shack, they don't have any caps under 35v and the 35v
2200uF is $4 each so it's $12 just to replace the 3 caps. I've decided to
junk the whole thing (after ripping out the fan) and save myself the
trouble. No way of knowing what other caps are going to fail.

 

[James Sweet]

I've checked Radio Shack, they don't have any caps under 35v and the 35v
2200uF is $4 each so it's $12 just to replace the 3 caps. I've decided to
junk the whole thing (after ripping out the fan) and save myself the
trouble. No way of knowing what other caps are going to fail.

Radio Shack is useless, if you order the parts online the caps will be about
$0.50 each. Sounds like a really simple fix that was scrapped for no good
reason.

 

[Impmon]

Radio Shack is useless, if you order the parts online the caps will be
about

$0.50 each. Sounds like a really simple fix that was scrapped for no good
reason.

Not really, the power supply is a Deer brand. From what someone described,
I'm better off with a new one anyway.

 

[James Sweet]

Not really, the power supply is a Deer brand. From what someone described,
I'm better off with a new one anyway.

True enough. For the last few years I've paid attention and only bothered to
buy quality power supplies, seems like it didn't used to make much
difference, they were pretty much all decent at one time.

 

[jakdedert]

My experience exactly. Back in the 'AT' era, I don't think I ever had a ps
failure. I've lost track of how many ATX supplies I've replaced.

jak

 

[Impmon]

My experience exactly. Back in the 'AT' era, I don't think I ever had a ps
failure. I've lost track of how many ATX supplies I've replaced.

I still have many AT supplies that still works. The only difference were
that many of the AT were often linear power supply I(ie: energy guzzler,
always hot) while ATX supplies usually uses switching mode (efficient,
generally cool) and under normal condition the AT should have had higher
failure rate due to heat.

I wonder if anyone has tried to go after the various Taiwain companies for
selling inferior caps that usually caused failures in power supply, mobos,
etc.

 

[James Sweet]

I still have many AT supplies that still works. The only difference were
that many of the AT were often linear power supply I(ie: energy guzzler,
always hot) while ATX supplies usually uses switching mode (efficient,
generally cool) and under normal condition the AT should have had higher
failure rate due to heat.

I wonder if anyone has tried to go after the various Taiwain companies for
selling inferior caps that usually caused failures in power supply, mobos,
etc.

Where have you seen a linear AT supply?? Even the original IBM PC 65 watter
was a switcher, as has been every one of hundreds I've come across. I
haven't encountered a linear PSU in a computer since the S100 bus days.

 

[Ian Molton]

I still have many AT supplies that still works. The only difference were
that many of the AT were often linear power supply

I've NEVER seen a linear AT PSU.

 

[Impmon]

I've NEVER seen a linear AT PSU.

I may be mistaken but a few AT power supply I've taken apart, they all had
transformer that took up about 1/4 the board. On the primary side there
were fuse and switch. Pretty much nothing else, not even a single
transistor. On the secondary side lots of big caps, transistors, etc. That
lead me to believe they were linear.

May have been a cheap brand power supply.

 

[Ian Molton]

I may be mistaken but a few AT power supply I've taken apart, they all had
transformer that took up about 1/4 the board. On the primary side there
were fuse and switch. Pretty much nothing else, not even a single
transistor. On the secondary side lots of big caps, transistors, etc. That
lead me to believe they were linear.

May have been a cheap brand power supply.

in order to deliver 150W (common for an AT supply) it would have needed to be much bigger than 1/4 the board I would think...

 

[Michael Black]

in order to deliver 150W (common for an AT supply) it would have needed
to be much bigger than 1/4 the board I would think...

That's the irony. It's cheaper to have the switching supply, even
with it's more complicated electronics, than to have a linear supply,
once you get above a certain current level.

All those S-100 bus computers in the early days of home computers
had linear supplies, and they had hefty transformers. For some
reason, switching supplies did not appear, despite the benefits.
Apple broke away, going with a switching supply that resulted
in a much lighter computer. And while it likely cost more to
develop that supply, the cost per supply must have gone way down,
even with those extra parts, because the transformer for a linear
supply was a very costly item.

Michael

 

[Asimov]

"Impmon" bravely wrote to "All" (18 Dec 03 13:25:56)
--- on the heady topic of "Re: What a bonehead!!! (repairing P PC PS)"

Well, you are partly right, all pc psu's are 100% linear up to the main
filter capacitors! (g)


Im> From: "Impmon" <[email protected]>

I've NEVER seen a linear AT PSU.

Im> I may be mistaken but a few AT power supply I've taken apart, they
Im> all had transformer that took up about 1/4 the board. On the primary
Im> side there were fuse and switch. Pretty much nothing else, not even a
Im> single transistor. On the secondary side lots of big caps,
Im> transistors, etc. That lead me to believe they were linear.

Im> May have been a cheap brand power supply.

.... Which sparks some mnemonic circuitry.

 

[James Sweet]

That's the irony. It's cheaper to have the switching supply, even
with it's more complicated electronics, than to have a linear supply,
once you get above a certain current level.

All those S-100 bus computers in the early days of home computers
had linear supplies, and they had hefty transformers. For some
reason, switching supplies did not appear, despite the benefits.
Apple broke away, going with a switching supply that resulted
in a much lighter computer. And while it likely cost more to
develop that supply, the cost per supply must have gone way down,
even with those extra parts, because the transformer for a linear
supply was a very costly item.

Michael

Yeah I once had an old S100 bus computer, the transformer was about 6" cube,
and weighed at least 20 lbs.

 

[James Sweet]

I may be mistaken but a few AT power supply I've taken apart, they all had
transformer that took up about 1/4 the board. On the primary side there
were fuse and switch. Pretty much nothing else, not even a single
transistor. On the secondary side lots of big caps, transistors, etc. That
lead me to believe they were linear.

May have been a cheap brand power supply.

That transformer was likely the filter choke on the AC line, the actual
stepdown transformer was likely so small you didn't notice it's presence.