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I was tearing open an old ATX power supply from one of my old computers today, because it was making a funny high-pitched wining noise.

I noted that several of the components within were starting fuse together into a sort of electronics mush.

My thought is that it's probably no-longer safe to use this power supply, so I swapped it out in the old computer I was using.

Here are a few photo of the component mush:

Three little components in their mushie state.

Now I guess my question is:

  1. Can I fix this?

  2. How long do I have to wait before the capacitor within has indeed run out of power?
    (it's a 350W ATX Power Supply)

  3. Is there any place to find out what components I need to replace them?

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  • \$\begingroup\$ Nothing to do with electronic design. Question will be closed. \$\endgroup\$
    – Leon Heller
    Commented Nov 19, 2011 at 22:59
  • \$\begingroup\$ Okay, so can we have this thing migrated over to SuperUser than? \$\endgroup\$
    – leeand00
    Commented Nov 19, 2011 at 23:01
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    \$\begingroup\$ It's not clear what that picture is showing. It looks just some stuff caught between components, but it's hard to tell. It that a dead moth or something? \$\endgroup\$
    – Olin Lathrop
    Commented Nov 19, 2011 at 23:02
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    \$\begingroup\$ Could be leaked electrolyte from a bad capacitor? Though if it has volume, I'd consider some kind of bonding goup or even a contaminate from an external source more likely. \$\endgroup\$
    – Chris Stratton
    Commented Nov 19, 2011 at 23:50
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    \$\begingroup\$ Considering the price of power supplies, and the associated dangers, you probably will not want to bother repairing it - i usually harvest the heat sinks on better grade ones, but really, the dangers associated with trying to fix a PSU don't make it worth it. I also note some PSUs use some kind of silicone gunk to keep parts apart - i've seen cases where heatsinks were at high potential (and certainly felt it) and all that seperated that heat sink and gunk was a blob of silicon. Just spend the 20 dollars or so on a cheap and cheerful power supply for experiments and decent ones for use. \$\endgroup\$
    – Journeyman Geek
    Commented Nov 20, 2011 at 3:54

2 Answers 2

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Can't make out what the picture is supposed to be of, but the mush you refer to is likely some thermal compound or adhesive.
It's probably one of the inductors or transformers on the board, which can vibrate slightly when passing a switching current. This is called magnetostriction. Capacitors can also buzz but it is more likely to be the magnetics.
It is not an indicator that the power supply is faulty. You can dampen it by making sure the magnetic components are solidly fixed to the PCB (e.g. with the adhesive mentioned above)

I don't advise trying to service it yourself (no need if it's not faulty anyway) but just in case and since you asked: You probably want to wait at least ten minutes (the longer the better) after unplugging the supply, and then make sure no significant charge is left in the large capacitors. Most large caps will have a high value parallel "bleeder" resistor across them so they discharge slowly when power is turned off, but do not rely on one being present and working. Some capacitors can hold a charge for days if no means of discharge is present.
See the section "why this matters" and "discharge technique" on this page for some decent info. Be very cautious, you can receive a lethal shock from a large filter cap, or they can explode or even vaporise metal.

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  • \$\begingroup\$ I've been on the business end of a charged cap from a power supply - one of the scary moments I've had. \$\endgroup\$
    – rfusca
    Commented Nov 20, 2011 at 2:21
  • \$\begingroup\$ @rfusca me too. There was a drain/balance resistor but it had failed open circuit (which was why the power supply was misbehaving) \$\endgroup\$
    – Peter Green
    Commented Dec 23, 2015 at 14:31
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I would never fix a power supply to save few bucks to use it again in your existing computer! If you like to use it for some other projects that do not cost as much as a computer, just replace the bad parts with new parts. BUT, these power supply's are not met to bee fixed, because once few components, like capacitors, start to go, you will have other parts go bad very soon. That is what I do for my computers and for my customer computers also.

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