My first ever PSU repair

[Rulycat]

You wouldn't think so, but I never actually repaired a PSU. More interested in the theory and cash strapped.

So tonight I tackled a Casecom 350w as my test subject, this had two bulging caps, both JEE. The replacement caps were a Teapo and a H cap. The "H" brand cap was 25v so it had to be squeezed in a bit. I didn't care too much about the make as I wanted it to work first and not waste money on good caps.

The 5VSB was waivering between 5.1 and 5.4v according to my Xilence PSU tester.

Main caps are 820uf 200v CS. Other caps are a mix of JEE and JP or something like that.

This isn't going to be used in an actual computer, it's future purpose will be for testing ideas I may have. With the caps I put in, definitely NOT in MY computer!

I think it's a powmax but not sure. Also, look at the Teapo, it looks rather odd, looks like some sort of resleeved Jamicon or does Teapo also use this vent? These were my dad's grab bag of caps he got from eBay and like I say it worked afterwards and I don't intent to use it seriously. But it DOES power up my test PC and 5VSB now is settled on 5.2v.

Arrows are pointing to the new caps in pic 5.

Behold, pics!

[c_hegge]

Re: My first ever PSU repair

It actually looks more like a Sun Pro to me. Good job fixing it (but you know what I think of cheapo teapo and unknown brands of caps).

[Rulycat]

Re: My first ever PSU repair

It could well be, it reminded me of this:
http://www.slcentral.com/powmax-demon-580w-psu/

Casecom are common around here, they have 300w-500w models, all pretty much the same as this but they upgrade the cap values etc. Though this is from 2005 and the 2011 300w model I have has thinner heatsinks, so I reckon they've been cutting corners.

What's your thoughts on that Teapo? The vent doesn't look very Teapo-like?

[Rulycat]

Re: My first ever PSU repair

Actually I think these new caps were GP, I didn't check the series.

[mockingbird]

Re: My first ever PSU repair

I'm in the process of ordering caps for various PSUs I have lying around that I've already prepared for recapping...

Question:
How can I measure the capacitor voltages while they're still in the PSU? I'm trying to see if I can get away with skinnier, lower voltage caps in several spots where the equal spec is unavailable and was probably custom order... Do I put red DMM wire on cap + and common DMM wire on any ground in the PSU or on the negative cap lead?

Which wire should touch first, red or black?

[popeye]

Re: My first ever PSU repair

never ever use lower voltage than what is specified

[370forlife]

Re: My first ever PSU repair

I'm in the process of ordering caps for various PSUs I have lying around that I've already prepared for recapping...

Question:
How can I measure the capacitor voltages while they're still in the PSU? I'm trying to see if I can get away with skinnier, lower voltage caps in several spots where the equal spec is unavailable and was probably custom order... Do I put red DMM wire on cap + and common DMM wire on any ground in the PSU or on the negative cap lead?

Which wire should touch first, red or black?

If they are just secondary filtering caps, trace the positive lead's solder plane and see what set of wires it goes to. If it goes to the 12v wires, then 16v is as low as you should go. If it goes to the 5v, I would stick to 10v caps but you could get away with 6.3v. If it goes to the 3.3v wires, 6.3v is fine. If it filters the 5vsb same as the regular 5v rail, 10v or 6.3v in a pinch. Anything else I wouldn't change the voltage on.

[mariushm]

Re: My first ever PSU repair

Ignore the above (popeye's) post.

I've measured with no problems the voltage by putting the probes on the capacitor terminals - by default I touch the ground plane first but it's just a habit, I don't think it would matter.

I don't think it's a good idea to connect the common probe to the ground of the whole board.

Yes, you can go to capacitors of lower voltage but sometimes they intentionally choose them like them due to lower ESR or higher ripple. You should be able to get newer capacitors with equal specs.

ps. I just saw you talk about power supplies... the advice above is for general circuits... in power supplies you only have 3.3v , 5v and 12v so capacitors rated for 6.3v should be the smallest you use.

[c_hegge]

Re: My first ever PSU repair

never ever use lower voltage than what is specified

He didn't

[Rulycat]

Re: My first ever PSU repair

Anyone have opinions on my suspicious teapo?

[mockingbird]

Re: My first ever PSU repair

Great advice guys... I will try what 370forlife said... to trace it back to the wires so that I don't have to measure...

Can anyone point me to a simple diagram showing me which wires are what voltage?

[370forlife]

Re: My first ever PSU repair

Anyone have opinions on my suspicious teapo?

Fake. Any Teapo you see in a power supply made in the last 10-15 years will have the three lines with three dots between them vent stamp. Hermei uses that vent stamp, but so does countless other yet-to-be-discovered small chinese electronic component companies willing to put a fake sleeve on their product. Large(r) OEM's (like sunpro in this case) like to use the small companies as suppliers as they are cheap and they wind up being their largest customer and can therefore control the company and their product.

[c_hegge]

Re: My first ever PSU repair

Anyone have opinions on my suspicious teapo?

Who cares? they're bad either way. that said, though, teapo do sometimes have that vent

[370forlife]

Re: My first ever PSU repair

Great advice guys... I will try what 370forlife said... to trace it back to the wires so that I don't have to measure...

Can anyone point me to a simple diagram showing me which wires are what voltage?

Generally yellow = 12v, red = 5v, orange = 3.3v, purple = 5vsb, though some of the higher end companies like delta and astec (you know, the ones you don't have to recap) may use different colors like brown for 12v (some astec), etc...

[Phaihn]

Re: My first ever PSU repair

I resently replaced a bunch of bulging caps in a psu from one of the used computers i have and it still works.

[momaka]

Re: My first ever PSU repair

Anyone have opinions on my suspicious teapo?

I agree with 370forlife - the Teapo your dad got from eBay are fake. Doesn't really make any sense why anyone fake an unreliable cap, but I guess that's just cheap Chinese companies.

Hermei uses that vent stamp

Hermei also uses the Panasonic "T" vent.

[370forlife]

Re: My first ever PSU repair

I agree with 370forlife - the Teapo your dad got from eBay are fake. Doesn't really make any sense why anyone fake an unreliable cap, but I guess that's just cheap Chinese companies.


Hermei also uses the Panasonic "T" vent.

I forgot about that. Come to think of or I haven't seen a hermei use that stamp in a while. They might be NOS hermei caps that have been resleeved or some backwards Chinese oem.

[Rulycat]

Re: My first ever PSU repair

About the Teapo...

SC105C (series and temp)
A8 (??)
02/99 <- hmmm, an old batch?

[370forlife]

Re: My first ever PSU repair

I have some from a old hipro with 98 datecodes (that are still good btw,) and they do not use that vent stamp. The even older teapos use a light blue sleeve and they even use the three line three dot vent.

[Rulycat]

Re: My first ever PSU repair

Well that's very, very odd. Why someone would fake a teapo I do not understand. Maybe they will be useful in extremely light load applications like clocks.