Reversing spring reverb input & output cables

[Billy Z]

Have you swapped the input/output leads ? what is the result ? if that does not fix the reverb you will need to get out the multi meter and a transistor tester will be handy. Check for +15v at C43 and -15v at C44 and C48. That is just a start.

[WimWalther]

Have you swapped the input/output leads ? what is the result ? if that does not fix the reverb you will need to get out the multi meter and a transistor tester will be handy. Check for +15v at C43 and -15v at C44 and C48. That is just a start.

The amp is currently disassembled waiting on parts.. Much of the front panel hardware was rusty (sat in basement or cold storage?) and I'm replacing it. That, and it's not designed to be worked on in-situ. There's little to no access to the (four) PCBs or front panel controls.

I ohmed out the tank and found 35R & 120R DC for the tank coils. Assuming the low figure is Input, I checked the schematic vs. PCB and found that the driver circuit (bjt pair) is in fact connected to the Input, and recovery (opamp) to the output.

[pauln]

The confusion is not being sure of the connection convention.

In the world of electric guitar pedals the convention is that with a series of pedals the previous pedal's output is connected to the subsequent pedal's input, and they are labeled as such. This is a pretty universal general connection convention, "out from one in to the next"...

For some reason Fender amps' connections to their reverb tanks used the convention that the input of the tank is connected to the connection labeled reverb "input" on the amp (as if the amp reverb connection label is indicating the target connection label on the tank), and the output of the tank is connected to the labeled reverb "output" on the amp... so verbally matching input to input and output to output, which makes no sense electronically, but perhaps had a certain peculiar clarity on the manufacturing assembly floor.

Not sure how other companies have labeled theirs...

[WimWalther]

I once did a full rebuild / repair on an Elk amp head, which I believe is a Japanese Fender copy.

Iirc, it had this same odd convention wrt the reverb tank. Don't quote me on this.

[kawa]

”Equipment Notation”
[Amp Side]

OUTrive for Reverb Tanks Drive Transduser

IN:Receive from Reverb Tanks Output Transduser

Spring Reverb Unit

[Tank Side]

Meaning

IN: Driive Circuit from Amp

OUT: Receive Circuit to Amp