Switching PSU noise on +12V for CPU

[eccerr0r]

Re: Switching PSU noise on +12V for CPU

Weird. I cannot find 16V caps on this Foxconn M/B, maybe it does not have prefiltering and depends on the PSU to do all the filtering?

I also checked the ATX24 power plug. Holy crap, I see 600mV droops on this wire that aren't visible on other wires.

And those fake Nichicons. I tried repeatedly rapidly manually charging/shorting one of them, yes the cap starts getting warm. Maybe expected, but when I set my bench PSU to about 14V I see about 300mA leakage on a 16V cap. This is NOT right...

[eccerr0r]

Re: Switching PSU noise on +12V for CPU

Hmm...Since my Sencore also has a "reform" function, I wonder what it will do with these leaky caps....
I need to stick it in a blast chamber and see what happens when I let it reform for a while. This cap shouldn't be all that old...

[kaboom]

Re: Switching PSU noise on +12V for CPU

when I set my bench PSU to about 14V I see about 300mA leakage on a 16V cap. This is NOT right...

Thinking outside the box, it makes perfect sense when you consider those are fake caps...

Not 16V rated at all.


FWIW, I have "torture tested" several Nichicons out of various equipment I junked. I applied 18V to several PW, VR, and HM 16V caps, from 100u to 4700u, and after a few minutes, leakage in most cases was below 10mA, with the 4700u/16V VR ultimately withstanding 20V with less than a mA of leakage.

Again, these were used caps from junk equipment.

Legitimate "16V" caps are usually formed to withstand 20V; the old datasheets would list these as 16V rated/20V surge.

As for the fake caps, they'll have whatever printed on their sleeve that looks or "feels" good, depending on their intended use (mobo, SMPS, etc).

[Wester547]

Re: Switching PSU noise on +12V for CPU

16v is too low for a 12v line - even if a few people will now start flaming me over saying it.
also, if that cap has been sitting for over a year it may have started to depolarize.

i had that the other day, dug out a working board that i stored a couple of years back,
powered it up - BANG - fucking teapo 6.3v cap on the 5v rail!!
replaced the bitch and a matching one with a pair of 16v rubycon's

The Teapo capacitor likely bulged because it's crap and no other reason. Teapo capacitors are sometimes known to outgas without ever having _any_ bias applied to their plates (in storage). It does hold true that capacitors from crap brands (nevermind counterfeit capacitors) are more likely to be overrated, not just in terms of voltage and capacitance but in terms of ripple current in the datasheets (which in and of themselves tend to be amuck with sloppiness and inconsistent values).

And IMHO, if 16V was really too low for the +12V input (or output), for wet electrolytics, expedited failures, even from good brands and series, would be more commonplace. Leakage current does augment as you approach the rated voltage, and that in turn causes the consumption of electrolyte to rise so as to correct defects (even those minor) in the oxide layer (reforming). I like the fact that those recent HMs survived voltage torture testing. I wonder if any KZG could survive and brave the same challenge?

[eccerr0r]

Re: Switching PSU noise on +12V for CPU

I hooked up one of these fake caps to my Sencore with 15V reform voltage. Currently it's leaking at 2.8mA, so at least it seems a bit lower than when I was testing with my bench psu. Measuring the voltage with a DMM it looks the Sencore is at 11.8V, so perhaps it hasn't gotten up to the voltage where it was leaking really badly.

The only "good" think is that this cap does read 3300uF±20% at 3500uF... but the voltage rating is really wrong.

Oh BTW, the fake cap took less than 10 minutes of bias at 12V to vent. I pity whoever actually used these as 12V filter caps...

[eccerr0r]

Re: Switching PSU noise on +12V for CPU

OH FUN!!!

After about 8 hours, the cap that I stuck on my Sencore decreased to 1300µA leakage... Voltage went up to 13V...

BUT it BLOATED!!! It'll explode any time now!

This is NOT a 16V cap!

And fun... I just noticed these fake Nichicons that I have, they're all sorts of different capacitors from different manufacturers. Looks like the counterfeiter used caps from all companies, so you never know who made that counterfeit. Will have to setup another thread...

[kaboom]

Re: Switching PSU noise on +12V for CPU

You've been on BCN since 11/08/2012 and you're just figuring that out?!

[eccerr0r]

Re: Switching PSU noise on +12V for CPU

Look if you don't want to respond, you don't need to respond. No sense in personal attacks which are absolutely the most useless posts around.

In any case, to reduce a counterfeiter's costs, one would expect to stick with one large lot and not actually mix them. Or at least have enough of them such that they are very uniform to any one seller.

This is not as uniform as I expected, when I first looked at these they appeared mostly the same (I did notice one anomaly the first pass), until the closer inspection now I see even more within the same batch.

Once again I expected these to at least be close to spec and not blow up in 10 minutes; 10 weeks or 10 months, maybe. After all Dell did not see their computers blow up in 10 minutes else it would have been caught in burn-in.