wrote in message
...
Replace some of the ones that read 0.2. They are probably a bank of caps.
The common thing is to use a bunch of them in parallel. You can confirm this
by meter. Of course all the negatives will read continuity, but in a bank
of caps, both leads will read continuity.

If you have a bank of five caps, 0.2 ohms ESR is too high and that's one of
the reasons they used so many. Another is ripple current.

When you have this, you can just replace a couple in a bank to see if it
cures the problem. In fact when it gets to that point I don't even clip the
leads off, I just let the replacement(s) stand up off the board. If the
problem is fixed, then I sink them down and snip them, and of course replace
the rest.

The one you replaced was obviously by itself. The others are probably a bank
of five and they are probably off the output of a switching regulator. They
might be running at like 2 volts and anywhere from 2 to 20 amps depending on
processor load. The math says 0.2 ohms is way too high. Say it's 3 volts at
10 amps. That's like a 0.33 ohm load approzimately. That could make the
ripple voltage almost half of the supply concievably. Coming off a high
speed switching regulator, that is quite noisy and the data will be FUBAR.
Temperature will also affct it.

If you find those five caps are just all in parallel, the ESR should be
practically imeasurable.

If it doesn't work, that's why you didn't cut the leads on the replacements.

Hi,

I'll have another look at how the caps are wired. Some are located close to
each other but at first glance you wouldn't think they would be in parallel.
I'll report back my findings.

Thanks for your reply.
--
David Farber
Los Osos, CA