I've been following the electronics newsgroups for some time, and decided to
try a small repair job. I have a 20Wx2 small single-board amplifier which
has only worked on one channel since it was given to me. Due to its' small
size, I'd like to repair it. Anyway, I used a DMM to test each of the 20 or
so electrolytic capacitors on the board. I know, I know, you can't really
test them in the circuit and expect a 100% accurate result. But as it's a
two-channel amp, I figured that at least the equivilant capacitors in
Channel A and Channel B should exhibit identical behavior.

I located two 470uF caps which differed in that one of them had zero
resistance which did not rise, even on the highest resistance scape of my
DMM, 20M ohm, as did all of the other caps. So, I figured I'd swap the two
identical caps (channel A and channel B). I tried using desoldering braid
(which I've used many times with great results) and found that the solder on
this board just wouldn't melt with my 30W iron. Well, says I , I'll just
use a bigger stick. I grabbed the 45W iron and still couldn't seem to melt
the solder through the braid, although the 45W iron WOULD melt the solder
directly. I heated each lead and wiggled and jiggled it loose. When I had
both caps removed I put the desoldering braid directly over the hole in the
PCB and with a pointed tip leaned on the board until the braid cleared up
the solder. This took maybe a minute or more of continuous heat.

When I removed the brad, AAAAGGGHH, it seems to have removed all of the
metal around the hole, not just the solder. Now the trace itself to which
the cap is connected is on the other side of the board and I could put in a
cap with slightly longer leads and solder it on the top. But if there's a
way to fix what I've done that'd be even better. When I put in the original
cap the solder just won't seem to go into the hole any more, it just sticks
to the iron.

Any advice greatly appreciated, I suppose this is how folks learn.

BTW, when I got both caps out they tested identically out of the circuit so
I'm pretty sure my problem is elsewhere. The circuit consists of a simple
power supply, unregulated, a whack of tiny (mainly 10uF 50V) electrolytic
caps, some mylar caps, resistors, a bass/treble IC, two 20W TO-220 amplifier
chips. I can very very faintly hear sound in the bad channel. When I turn
the volume up and down on the bad channel it makes a sort of "thumping"
sound from the bad speaker but doesn't amplify the sound. I've replaced the
amplfier chip on the bad channel as it was cheap and simple but this did not
help. Anybody have any suggestions what to check next? I do not own an
oscilloscope. I have checked and cleaned all of the knobs (bass, treble,
balance, volume), they all work as they're supposed to.

Thanks

Dave