"David Farber" wrote in message
...

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


I had to use my Weller 100/140 watt gun to generate enough heat to get the
capacitors out. Even with flux and SnPb solder it was a chore. The results
were, one was 1.3 ohms and the remaining four measured from 4.7 to 5.0 ohms.
I will order the replacements and report back.

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