Hey guys!

So a few weeks ago I picked up this amp from my dad's friend. He said if we restore it I can keep it.

It's a Japanese Guyatone GA1100 Reverb Custom from the early 70s!

Apologies for the poor camera quality, I didn't have the good camera at the time. But I will upload some good quality ones tomorrow.

2 Inputs
Bright Switch

2 Inputs
Bright Switch
(tremolo) Speed
(tremolo) Intensity

4 Mullard EL84 power tubes
6 preamp tubes
reverb tank

Now we defiantly know somebody's been poking around in this amp before. This was shown by different resistors and caps being changed. Now the person who was here before may have just changed some caps and stuff that may have blown, and general maintenance.

But this person made a very noticeable change, but were not sure why. He put in another transformer that goes right after the power section. You can see this below:

Here's an original GA-1100

Now here's mine
What condition is it in
We got the amp slightly working by connecting some disconnected wires. A sound was coming from it but not all features were working. The tremolo wasn't working. When we took out the speakers we noticed tears in them.

The outside is cosmetically in an OK condition for an amps this old but my dad insists on making it look new.

Each speaker ways more then any other speaker I've had or seen before, just look at the size of those magnets!
The amp as a whole is insanely f***ing heavy! As in unliftable heavy! So some recessed cabinet handles will be necesary.

What we've done already:
-Changed some caps and resistors.
-Fixed small tears in speakers. This was done by using coffee filter paper and a latex based glue (we used copydex).

What has to be done:
-Replace all pots
-New optocoupler
-New tolex
-New grill clothe
-(possibly) new tubes
-Further diagnosis and research of other problems
-Recessed cabinet handles
Last edited by R_Gallagher_Fan at Mar 9, 2013,
Hi there. I have 2 Guyatones, a GA-1100 and a GA-1100D. Yours is an interesting mix of the GA-1100 and the GA-1100D, maybe a transitional model, since it does not yet have the mastervolume that came in the GA-1100D and has the Output transformer still in the same place as a Fender Twin (the GA-1100D has the OT moved to the far right) but it already uses the later PCB-board lay out. Interesting!

I restored my GA-1100D, my GA-1100 is al original. They both sound killer and just as good as any Twin. If I were you I would return your amp back to it's original state, with good quality caps and the right type of resistors in the right place. It's original state is actually almost completely identical to a Fender AB763 Twin Reverb schematic.

You might want to join the Guyatone Vintage Amps facebook group? Lots of information there! There you will also find the schematics (if you haven't already found them on the web).


Oh, the powertubes are not EL84, but 6L6GC (but some models came also with EL34, maybe you mean those?)
Hi, thanks for the info. That's interesting about the two style amps being mixed together. We really think it is a transitional model because of further inspection of the chassis there is a hole where the master volume should be but on the front plate there is no hole for it.

Also. This amp has finally started working over the weekend as most of the caps have been replaced. The only problem is the reverb isn't working properly.