Encounter with bad caps.

[Zotin Khuma]

I've been reading about bad capacitors for months (more ?), all the
while building dozens of computers for friends and business clients
with nary a problem. I was beginning to wonder if the thing had been
blown up out of proportion, then wham, two of them yesterday - both
Leadtek K7NCR18GM's. Fortunately, they're located almost next door in
an internet cafe owned by a close friend who, also fortunately, is
quite knowledgeable about computers and understands the situation.
Again it's fortunate that I've used only a handful of this particular
model.

These mobos were bought in January this year, but to claim the
warranty I'd have had to send them to a city >500km away and wait
perhaps 3-4 weeks. The owner said he preferred to have me repair them,
but I don't stock 1000uF 6.3V caps in that size and couldn't find them
anywhere in my town. So I replaced them with 220/10 caps and they're
doing fine so far. Not ideal certainly, but at least such filter caps
usually aren't critical in value.

I also noticed that the 5-volt pin of the ATX connector was badly
burnt in both cases. It might have been possible to clean the male pin
on the mobo but the female on the PSU connector was a different
matter. So I soldered a 10-inch length of thick flex wire to the
5-volt line above the female connector and soldered the other end to
the bottom side of the mobo, taking care to make a good solid
connection since the 5V line carries a heavy amperage. The owner
doesn't care so long as they work.

Seems to me that whenever someone mentions the number of caps that
went bad, it's usually 7 to a mobo. Same number in my case - two pairs
and three singles. There are also other 1000/6.3 caps on the mobos but
they looked healthy so, not having the proper replacements, I left
them alone. I'm also inclined to think that the crashes were caused by
the bad 5V connection rather than by the caps directly.

I'm posting this just in case someone else with a similar problem
finds a bit of useful info here.

 

[John]

These mobos were bought in January this year, but to claim the
warranty I'd have had to send them to a city >500km away and wait
perhaps 3-4 weeks. The owner said he preferred to have me repair them,
but I don't stock 1000uF 6.3V caps in that size and couldn't find them
anywhere in my town. So I replaced them with 220/10 caps and they're
doing fine so far. Not ideal certainly, but at least such filter caps
usually aren't critical in value.

Im surprised because iD read about this in the abit groups AGES ago
and there were claims that many firms cleaned up their act a long time
ago. Abit now says they dont use and cheap caps at their website.

So that would mean it was more widespread that I thought and it was
going on a lot longer than I thought.

I personally have not seen it (swollen or leaking caps) except once
AGES ago , I mean a years and years ago in a Power Supply in a
SuperMicro case that a neighbor had . He says it made POP sound and
then sparks shot out and smoke. I looked at it and there was brown
fluid leaking out of a cap. OF course maybe some of the weirdness Ive
had in some many boards was caused by bad caps but I couldnt tell from
just looking at them.

 

[kony]

Im surprised because iD read about this in the abit groups AGES ago
and there were claims that many firms cleaned up their act a long time
ago. Abit now says they dont use and cheap caps at their website.

So that would mean it was more widespread that I thought and it was
going on a lot longer than I thought.

I personally have not seen it (swollen or leaking caps) except once
AGES ago , I mean a years and years ago in a Power Supply in a
SuperMicro case that a neighbor had . He says it made POP sound and
then sparks shot out and smoke. I looked at it and there was brown
fluid leaking out of a cap. OF course maybe some of the weirdness Ive
had in some many boards was caused by bad caps but I couldnt tell from
just looking at them.

IN addition to the caps with the incomplete electrolyte
formula (if that rumor is true), there has been a transition
period with systems using ever higher current and partially
facilitating that is the drop in voltages. Caps that
might've be suitable for old systems just didn't have low
enough ESR for more modern systems and heated up too much.

That (and other factors like overclocking or poor system
power supply, cut-rate motherboard designs (or simply stupid
flaws, for example when a power supply load resistor is
cemeted to an electrolytic), reduction for the sake of
cost-cutting) put more wear on a cap. Add to that the
situation where an off-brand may have worse quality control
and there may be a lot of failures that relate to inferior
quality in one way or other, but it may be splitting hairs
to call them defective, especially since some of the brands
don't seem to have readily available manufacturer's specs
beyond what's printed on their sleeves. In such cases some
of the caps may be meeting their specs but external forces
cause the failure.