1959 Gibson GA20T Cap job

Kirk · Posted: Sun Jul 15, 2007 10:38 am Post subject: 1959 Gibson GA20T Cap job

Hi,
I have my amp at a technicians shop and he was telling me that caps are hard to come by for the old gibson amps because they did not make enough to justify production of repcacement parts for the old 50's models.
Could anybody shed a little light on this?
NOS caps cant work as they would dry out also.

Thanks, Kirk Shocked

tw001_tw · Posted: Mon Jul 16, 2007 5:45 am Post subject:

Is the tech going for 'period correct' looks ? That might be the issue, not
just correct values. By randomly selecting some older Gibson schematics
for review (http://www.discovercircuits.com/M/musical1a.htm) I did not
see any odd-ball (unavailable) values. What model do you got?

Kirk · Posted: Mon Jul 16, 2007 7:02 pm Post subject: GA20T

He does want to try to keep it correct as far as values goes, the amp is a
1959 Gibson GA20t with a Jensen 12'' ALNico speaker. It does have tremelo.
There was confusion on the large caps as he said they were not cap cans as three wires came out of one.
All I want is a sweet sounding old Tweed amp, he seemed to think that the caps in there would not allow enough room for new ones with the same values.
I hear of every one else geting it done to there old amps, I am hoping for a nice garage amp, stored well and used.

Thanks for posting the site I will check it out.
Kirk

SAguitar · Posted: Tue Jul 17, 2007 7:35 am Post subject:

I'm confident your goal is achievable, although I've never encountered a cap with three wires coming out of it.
_________________
"I love the smell of hot solder in the morning. It smells like victory."

Kirk · Posted: Tue Jul 24, 2007 11:05 am Post subject: Cap job GA20T

I have the amp back and it sound very nice, it really cranks out the sound with a warm tone and a early breakup.
The caps are what he calls a multi cap,he showed me the configuration of the old versus the new.The new one has one lead from either end the old has three out of one side. He would have had to stack caps of the new style to get the same values and route wires near the transformer and and back to the same points.
It turned out that the multicap in question is OK for now, and he just replaced what was bad.
I have a standard of sound that I want t achieve for the rest in need of work. At least close to it.

Kirk

SAguitar · Posted: Tue Jul 24, 2007 11:26 am Post subject:

Well, congratulations, Keith! I'm real glad it worked out for ya! Very Happy

_________________
"I love the smell of hot solder in the morning. It smells like victory."

tw001_tw · Posted: Tue Jul 24, 2007 3:44 pm Post subject:

Glad it worked out for you.

And for the technical wrap up - there are 3 filter caps - two 20uf and
one 10uf. Electrically, you can use 1 20uf, another 20uf and a 10uf - OR
you can use a 10uf/20uf/20uf cap can - or pretty much any combination
of the 3. As long as the values don't change, all will be well. And even
if the values do change (say replace the 10uf with a 20uf) the difference
will be little. But as long as its working and your happy with it, what
more could you ask for, huh? Cool

http://www.freeinfosociety.com/electronics/schematics/audio/gibsonga20t.pdf