Looking for schematics for a Risson Gp-120 - 1980's SS amp

[Saransk93]

Pick this up for basically the postage. Large amp, built like a tank

Has a Dis-Stain (distortion/sustain) input with a Response control and a Normal input
Besides a Bright & Middle switch, it has one marked R.S.E
The sustain has 3 settings - Norm/Rock/British and a Vari-power control hooked up to a large honking resistor (broken)

Some of the control look like the old Rickenbacker Tri-Sonic (same designer).
Enough non-"standard" controls that I'd like a schematic to help restore it.
Can't find much about it on-line and emails to the company have not been answered - the designer is still in business.

Any help would be greatly appreciated
Mike

[J M Fahey]

1) your best bet is still the original designer.
Just donīt push him, be very polite always, designers are proud of they creations and I bet he will eventually answer.

2) that said, designers have "pet ideas" which are often repeated all over the place.
From your description I bet itīs very close (the evolution of) his famous Rickenbacker Transonic amplifier, whose full schematic is online, I just checked it.

Maany "quirks" found in yours , are also in the other ("pet ideas" ), including the Fuzz circuit (probably with 3 fixed EQ settings instead of the original single one), 3 pushbutton selectable "fixed graphic Equalizer" settings, etc.
Others are new, such as the Vari-Power (an attenuator?)

Justv to start "doing something" Iīd download and print the Transonic on a big sheet (better 2 standard sheets taped together, one half on each) and start comparing it to whatīs on PCB, you might be surprised.

In any case, what is the actual problem you are trying to solve?

Absolute worst case, IF amp is non repairable, you have a nice chassis, cabinet, power transformer and hefty power supply, gut it leaving just the supply and if you dare, mount a new amp in (choose some EBay module, even Class D, which is happy with around +/-45V rails, which is what I guess you have.

You would only have to build a preamp ... which might even be a Tube one, just get a small transformer able to feed some 12AX7 filaments and give you some 200/250V +V at only a few mA current (preamp tubes eat very little there).

Post a couple pictures, one showing outside, another showing guts.

From Risson site, they claim they used "only the best" such as Schumacher transformers (unheard of in Transistor amps) and Motorola (ON) transistors, so they "should" be very well built.
.

[Leo_Gnardo]

1) your best bet is still the original designer.
Just donīt push him, be very polite always, designers are proud of they creations and I bet he will eventually answer.

That oughta work. One of my crustomers picked up an old Risson tube amp, it looks like a cross between 60's Fender and Marshall. Somehow he got a hold of the designer/builder Bob Rissi & they had a good phone conversation. Though much of what he heard went over his head. The amp will probably find its way to my workbench one of these days. Here's a link to his inquiry on The Amp Garage, with photos:

http://ampgarage.com/forum/viewtopic...5&hilit=risson

[nosaj]

That oughta work. One of my crustomers picked up an old Risson tube amp, it looks like a cross between 60's Fender and Marshall. Somehow he got a hold of the designer/builder Bob Rissi & they had a good phone conversation. Though much of what he heard went over his head. The amp will probably find its way to my workbench one of these days. Here's a link to his inquiry on The Amp Garage, with photos:

http://ampgarage.com/forum/viewtopic...5&hilit=risson

What's crustomer?

nosaj

[Leo_Gnardo]

Crusty customer. Also an old fiend, ummmm friend.

[nosaj]

Crusty customer. Also an old fiend, ummmm friend.

Oh a shop rat.

nosaj