Any way to fix a power supply?

T

TehQuick

2[H]4U
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Jul 3, 2004
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my BFG LS 550 died, or so it seems. Whenever I try to turn on the computer, it gets stuck in an on-off cycle, i.e. fans spin up for a second then turn off and then turn on again. It continues for a few seconds even AFTER I hit the off switch at the back of the PSU. It does work once in a while but mostly it gets stuck in this cycle. I tried another old PSU, and computer booted up normally, didn't behave this way at all.

So the question is - since BFG bit the dust and no longer provides any warranty service, is there anyway I could fix it myself? I wonder if anyone encountered a similar issue and had any insight into how to fix this. I'm looking for a new PSU but I'd rather keep this one if the issue is (somewhat) easily fixable.
 
Sounds like it probably has a bad capacitor or two.

If you got some soldering skillz or know somebody who does, it is a very easy fix.

I usually use good caps out of other faulty electronics if I have something that needs caps. Other parts are sometimes canibalized as well.
 
Is there an easy way to tell which capacitor is bad? I do have some soldering experience although not with electronics lol :)
 
Are you an electrical engineer? If the answer to that question is no, then so is the answer to yours. PSUs are somewhat complicated devices, and unless you know exactly what you're doing, an attempt to repair one will likely cause more harm than good.
 
lol, gotcha :) Yeah, I cracked it open and I can't make heads or tails out of it anyways :) Seems like all the caps are alright but what do I know?
 
I think you should file a written complaint with the credit card issuer, mail it to the special address for billing problems, and claim this as a "billing error" because you bought a warranty but didn't get it. It's also possible that American Express, Visa, Mastercard, or Discover card extended warranty protection will cover the damage, and some debit card programs also provide extended warranties.

Here's an article about repairing PC power supplies. It's so old that it covers only AT PSUs, but the information in it is still useful: 1996 Nuts & Volts article

In most cases, a diode or transistor has shorted (can test with ohm meter) or a capacitor has gone bad (ohm meter will usually say it's fine, even when it's really bad). It's usually easier to unsolder everything on each big heatsink as a unit, including the heatsink, so you can reach each component (HardwareSecrets.com does this for almost each PSU review and has lots of photos). Not all the components on the big heatsinks are diodes or transistors; on the heatsink with the high voltage transistors there may be a 3-pin chip for the +5Vstandby supply, and on the heatsink with the low voltage diodes or transistors, you may also find a 2-pin device that's almost always a thermistor.

Except for the +5Vsb supply chip, replacement parts are fairly easy to find, and even parts from ancient PSUs almost anything of the same type with sufficient ratings (voltage, amps, power, etc.), and parts from even very old PSUs may meet all specs, sometimes including PSUs with much lower power ratings.

Be careful about the packaging of the components that attach to heatsinks because packaging determines how the parts need to be electrically insulated from the heatsinks. Some need a rubber insulator sheet plus a nylon shoulder washer, others need only insulator sheet, and some require nothing.

If you work on the PSU, don't apply AC power to it again except with a grounded 3-wire outlet and 3-wire cord AND only with the PSU's cover completely screwed together. I'm serious. There's lots of exposed, dangerous high voltage in a PSU, often including on some of the big heatsinks
 
Even if you can solder, diving into a PSU is dangerous. Plenty of the components continue to hold a charge after power is disconnected, so a stray tool can cause a very nasty shock that makes licking an electrical outlet look appealing.
 
You can repair it by gently picking it up and putting it inside a trash can. Then open the box of your replacement PSU and installing it onto your computer. Sorry, but consumer electronic goods are generally not fixable by consumers and not worth fixing by professionals. If it is not covered by a warranty, then move on.
 
jiminator said:
You can repair it by gently picking it up and putting it inside a trash can. Then open the box of your replacement PSU and installing it onto your computer. Sorry, but consumer electronic goods are generally not fixable by consumers and not worth fixing by professionals. If it is not covered by a warranty, then move on.
Click to expand...

Or you could recycle it instead.
 
Woofer00 said:
Even if you can solder, diving into a PSU is dangerous. Plenty of the components continue to hold a charge after power is disconnected, so a stray tool can cause a very nasty shock that makes licking an electrical outlet look appealing.
Click to expand...

This x 100! The capacitors in a PSU can hold a charge for hours, even after being unplugged. The Voltage and Amperage stored in them can KILL you if they discharge into you! My suggestion would be to replace and like the other poster here said, perhaps pursue recourse through your Credit Card company. Best wishes and be careful! :)
 
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