schematic needed: Gibson GA-45RVT Saturn - 60's guitar choob amp

In article <[email protected]>, Spud wrote:
> This is a model GA-45RVT tube guitar amp made by Gibson from 1965-67
> and was called the Saturn. It was a 2 10" speaker combo and featured
> Reverb/Tremolo, 2 6L6's, some 6EU7's, OA2, 12AU7.
>

Hi,

I have a book here - "Electric Guitar Amplifier Handbook", which has
the schematics of a number of guitar amps from that era (published in
1966) and include the Gibson Mercury Medalist. Has tremolo but no
reverb (as far as I can see). Inputs are 6EU7s going to 6FQ7 driver
into a pair of 6L6GC power tubes. There's also a schematic for the
Titan Medalist - a similar design but with a couple of 12AU7s between
the 6EU7 pre-amp and the 6FQ7 drivers, and 4 6L6Cs in the output.

If either or both of these are any help to you, I could scan and email
them to you.

--
Spence

On Sat, 21 Jun 2008 23:14:30 +0100, Spence
<spencelayhathotmaildotcodotuk> wrote:

>In article <[email protected]>, Spud wrote:
>> This is a model GA-45RVT tube guitar amp made by Gibson from 1965-67
>> and was called the Saturn. It was a 2 10" speaker combo and featured
>> Reverb/Tremolo, 2 6L6's, some 6EU7's, OA2, 12AU7.
>>
>
>Hi,
>
>I have a book here - "Electric Guitar Amplifier Handbook", which has
>the schematics of a number of guitar amps from that era (published in
>1966) and include the Gibson Mercury Medalist. Has tremolo but no
>reverb (as far as I can see). Inputs are 6EU7s going to 6FQ7 driver
>into a pair of 6L6GC power tubes. There's also a schematic for the
>Titan Medalist - a similar design but with a couple of 12AU7s between
>the 6EU7 pre-amp and the 6FQ7 drivers, and 4 6L6Cs in the output.
>
>If either or both of these are any help to you, I could scan and email
>them to you.

Thank you. I think I have one more source in NYC I can try. I'm not
really versed enough to interpolate from an approximate drawing and as
it's mostly the noisy, buzzing, microphonic and slushy sounding reverb
that's the problem I'd better try and get a diagram of that specific
part if I can. Thanks again for your effort.

In article <[email protected]>, Spud wrote:

> I'm not
> really versed enough to interpolate from an approximate drawing and as
> it's mostly the noisy, buzzing, microphonic and slushy sounding reverb
> that's the problem
>

In case you can't find an exact diagram, a couple of pointers. It's
probably a spring reverb unit, so it will be driven by a small
transformer driven by either a 6EU6 or 12AU7. You should be able to
trace the wiring through for that OK. The likely failures are going to
be either the valve or the electrolytic capacitors in that stage. If the
rest of the amp is OK, try working out which valves are where, and
switch an OK valve with the one driving the reverb. If the problem goes
away (or moves somewhere else), it's the valve. Considering its age, it
could be worth going through the amp replacing all the valves and
electrolytics any way if its not been done recently (in the last 10-15
years). Also, try giving the reverb spring casing a gentle tap - it
could be that the spring's stretched a bit. But bear in mind those
spring reverb units were noisy anyway, and I don't know how bad your
term "noisy, buzzing, microphonic and slushy sounding" sounds <g>.

> Thanks again for your effort.
>

YW, nice to know some of these great old amps are still around and being
looked after.

--
Spence