Bad solder joints and bulged caps, can one cause the other?

[twistedbottlecap10]

I opened up an Athena Power 500w AP-P4ATX50F12(rebadged topower p4 design) that had been in use for a couple of years to clean out the dust and try to figure out why it was suddenly shutting itself off at random times. I only saw one bulged cap and decided to try and replace it. I got to it easily as it was on the outer edge of the PCB near where the external wires are soldered and when I went to remove it in order to get the value of it(it had glue on the upper half). The cap(2200uf 10V) pulled cleanly out of the PCB with just a little bit of force applied and left two perfectly round holes in the solder joints. It is clear that the solder joint was bad as the legs of the cap appear to have no solder on them.

My question is: Did the bad solder joint cause the cap to bulge or did the cap experience enough localized heat over time to cause it to fail and the solder joint to weaken? Also, there were other smaller caps right next to it that look good(470uf 16v) that are the same unknown brand(solder joints are strong on those though).

The power supply had the following caps:
Teapo(primary)
Fuhjyyu (most others)
A few others (including the one that went bad) are an unknown brand that is black and has a + pattern on top, it has a symbol that I believe starts with a G with an underline that extends from the bottom of the G and continues straight across for several spaces. There are marks that emerge upward a couple of times from the underline that are supposed to be other letters , although I can't make out what they are supposed to be.

[Maxxarcade]

Re: Bad solder joints and bulged caps, can one cause the other?

Probably both bad caps and cold solder. A cap would likely explode before getting hot enough to unsolder itself. The bad connection was probably not helpful either. Was the fan working ok?

[twistedbottlecap10]

Re: Bad solder joints and bulged caps, can one cause the other?

Yes, both fans(80 & 120) were working fine, although they were temp controlled and tended to run slow so that they would be as quiet as possible. After dusting it out, all of the other components looked like new and showed no signs of anything overheating(no brown spots on the PCB or discoloration anywhere), just one bulged cap.

Thanks for the reply!

[Sparky]

Re: Bad solder joints and bulged caps, can one cause the other?

I wouldn't be surprised if they were related somehow (the bad joint causing increased resistance and such).

I would recommend replacing all the fuhjyyu caps. The Teapos are fine.

[twistedbottlecap10]

Re: Bad solder joints and bulged caps, can one cause the other?

I would replace the fuhjyyu's too if they were not so hard to get too. The heatsinks on this PSU are horizontal to the PCB and act like a roof(a low one at that) that covers the majority of the fuhjyyu caps. I don't foresee me trying to remove the heatsinks that are bolted down to other components to get to them when the fuhjyyu caps appear fine so far(reputation notwithstanding).

[Harvey]

Re: Bad solder joints and bulged caps, can one cause the other?

Probably both bad caps and cold solder. A cap would likely explode before getting hot enough to unsolder itself.

Not if you include time into the factor. I've seen countless dry joints caused by heat in the 50C-70C range and a few years of hot/cold cycles.

[twistedbottlecap10]

Re: Bad solder joints and bulged caps, can one cause the other?

The Athena 500w was run 24/7 for a little over two years now(first year with no UPS, second year with a Belkin 375va UPS-our power is pretty reliable with the exception of a handful of blinks during storms that are just long enough to cause things to turn off, hence the small UPS). It only started having shutdown problems(while doing nothing but sitting at the desktop) the last few months though(started getting progressively worse the last month or so).

[twistedbottlecap10]

Re: Bad solder joints and bulged caps, can one cause the other?

I went ahead and replaced the bulged cap with a Nichicon UHE1A222MPD(2200uf 10v) cap. I also changed out the old fans with some Antec single speed fans that I connected directly to the 12v line so they would run at full speed continuously. While I was at it I re-soldered some of the other connections near the area where the bulged cap was located to reduce the possibility of other bad solder joints being present. With the Antec fans installed and running full tilt the power supply is louder than it was, but it is also exhausting a lot more air. Hopefully the airflow is not so great that the air being pulled through the power supply can not adequately absorb the heat being radiated by the heatsinks and other heat generating components. All voltages look good when measured with a DMM and only time will tell if it is fixed. I am going to let it run 24/7 to see if it suddenly shuts down again and if it does it will be permanently retired.