Installing a reverb tank- '80s Yamaha G100-112 amp

Ben Elder · From: La Crescenta, California, USA

I'm trying to install a reverb tank in an 80s Yamaha G100-112 amp. (Whatever the correct Accutronics unit is--I looked it up once upon a time, then found one.) I've read some generic information on installing tanks and wonder what applies and doesn't apply here. (Fender and generic installations are different, apparently.)

Is the cardboard cutout that goes underneath necessary if I have a vinyl bag?

Do the screws go through the holes on the edges of the bag or through the holes in the tank's flanges?

Are the rubber grommets necessary with a tank?

The RCA jacks on the tank are clearly marked input and output but the RCA jacks on the amp chassis are (red dot) and (nothing). What does (red dot) indicate?

I've hooked it up without cardboard or grommets and the results are decidedly nothing to make me forget any Fender reverb amp I've ever heard. Reverb sounds like a small garage (thin, fast decay) rather than the great cathedrals of Europe.

I know where a used Hardwire/Digitech RV-7 at a good price is and I'm sorely tempted to wash my hands of the tank.
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Rick Batey · Posted 13 Apr 2012 4:45 am

Hi Ben, I have the schematic somewhere. Did I already send it to you?

The reverb on mine is somewhat better IMO than 'small garage', but I use a Dr Scientist pedal...

Ken Fox · From: Nashville GA USA

Is the cardboard cutout that goes underneath necessary if I have a vinyl bag?
A very good idea, as it keep the bag vinyl from damping the springs.

Do the screws go through the holes on the edges of the bag or through the holes in the tank's flanges?
Thru the bag ends or sides

Are the rubber grommets necessary with a tank?
They help space the springs above the cardboard a bit more and help avoid spring crash from stage vibrations. The older Fender amp even had wood strips under the tank edges for even further spacing.

The RCA jacks on the tank are clearly marked input and output but the RCA jacks on the amp chassis are (red dot) and (nothing). What does (red dot) indicate?

Not sure, but you can easily find the amp's reverb input cable by turning the reverb control up a bit and then touching the ends of the RCA cable. The one that makes noise goes to the tank's output RCA jack. The schematic for that section is below. Clearly shows the reverb control is after the tanks output side. The method above will work to ID the cable to connect to the tank's output. The DC resistance of the tanks coils are shown, not the AC impedance at 1Khz.

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