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Old 05-14-2011, 10:34 PM   #1
bw1
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Default Thermaltake Purepower HPC-420-102 DF

I've got a power supply here that's still working fine, but had the telltale high-pitched squeal. Opening it up revealed one visibly bad cap.

Looking for recommendations - I don't know that it's necessary to do a full re-cap? It's been in use for a good 4 years or more I'd guess, so I would think it if was going to be a problem it would be... but maybe that's a bad way to think about it.

Pictures attached. Anyone care to comment?
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Old 05-15-2011, 12:35 AM   #2
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Default Re: Thermaltake Purepower HPC-420-102 DF

I would recommend a full recap. That PSU is full of el-cheapo teapo, which are known fopr failing without bloating.
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Old 05-15-2011, 05:18 AM   #3
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Default Re: Thermaltake Purepower HPC-420-102 DF

Terrible work with the glue all over it. I would remove it carefully.
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Old 05-15-2011, 04:12 PM   #4
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Default Re: Thermaltake Purepower HPC-420-102 DF

Is it worth the effort? I'm ordering more caps later tonight and haven't checked if I'd have compatible ones here or would need to add more to the order.

A lot of "came with the case" power supplies I wouldn't bother with, but I know this one was a separate purchase at the time to upgrade a bit from the "case" model.
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Old 05-22-2011, 07:51 AM   #5
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Default Re: Thermaltake Purepower HPC-420-102 DF

Hello BW1. Where are you located?

The Thermotake power supply does not look that bad to me.

It would help to remove the glue which sometimes causes resistive paths. So I agree, spend some time removing the glue.

Works, but squealing. I would resolve the squealing problem before doing a recap. Looks like that bulging capacitor is the input filter capacitor for the 5vsb output "pi" filter. I would start by replacing that capacitor. If that solves the squealing problem, I wouldn't mess with the Teapo caps unless it is going into a machine that you want to keep a long time.

I have seen lots of Bestec power supplies, and several other brands which have the bulging 5vsb input pi filter cap bulging. Strange that the input capacitor is often bulging, but the output capacitor is OK. Until recently, I have felt that the blame was component location and heat. The capacitor on the Thermotake, like the Bestecs, is located between the two heat sinks. But this one doesn't appear to be touching any hot components. Is it possible that we have something else going on here?

We have learned about esr and its effect on capacitors and circuits. Esr is a resistance in series with the capacitance. There is also an inductance in series (or in parallel) with the capacitance due to the rolled foil inside to form one of the capacitor plates. This rolled foil does have an inductive effect. The coil and capacitor will have a tuned circuit effect, and as the esr resistive component increases, the loading effect more closely matches the source impedance. So as esr goes up, I would expect larger and larger oscillations. I still think heat is a culprit, but is it possible that the inductive characteristic of a wound foil electrolytic capacitor is a contributor to the cause of failure?

To eliminate any "inherent' oscillations caused by the construction of the capacitor, I would think that placing a .1 uF non electrolytic capacitor across the electrolytic capacitor in this location would solve a lot of the problem. Time for a response from our unique resident engineers.
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Old 05-22-2011, 07:14 PM   #6
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Default Re: Thermaltake Purepower HPC-420-102 DF

Quote:
Originally Posted by everell View Post
...Is it possible that we have something else going on here?...
Yes, the fact that the cap was an el-cheapo teapo
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Old 05-23-2011, 04:04 AM   #7
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Default Re: Thermaltake Purepower HPC-420-102 DF

The "fact" is.....are we working the problem or playing the blame card? I saw only one bloated capacitor. ALL of the other Teapo capacitors ARE BAD because ...................
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Old 05-23-2011, 04:32 AM   #8
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Default Re: Thermaltake Purepower HPC-420-102 DF

The others are probably still OK since they are not under as much stress as the bloated one, but I still think that if the bad one was a rubycon, it would have handled it much better.
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Old 05-23-2011, 04:35 AM   #9
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Default Re: Thermaltake Purepower HPC-420-102 DF

Quote:
Originally Posted by everell View Post

Works, but squealing. I would resolve the squealing problem before doing a recap. Looks like that bulging capacitor is the input filter capacitor for the 5vsb output "pi" filter. I would start by replacing that capacitor. If that solves the squealing problem, I wouldn't mess with the Teapo caps unless it is going into a machine that you want to keep a long time.

I have seen lots of Bestec power supplies, and several other brands which have the bulging 5vsb input pi filter cap bulging. Strange that the input capacitor is often bulging, but the output capacitor is OK.
The input cap of the pi filter gets most of the ripple from the switching transistors and that's the reason you see more often the input cap bulging not only on 5vsb, but also on 3.3V / 5V / 12V pi filter.
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