I could not see the pictures you are referring to... However I do see the links...
https://stefancarey.zenfolio.com/p553178115/hF606202E#hf606202e
https://stefancarey.zenfolio.com/p553178115/hF6062034#hf6062034
Each RCA cable has a signal and ground feeding signal to and from the reverb tank. Lets guess that the RED is sending signal IN (input on the reverb tank) and BLACK is sending signal (output on the reverb tank) back to the circuit in the amp. Drive circuit (I think is what it's called) sends to the input of the reverb tank and Recovery circuit (again this is what I call it) is the return signal from the output of the reverb tank.
Now as far as troubleshooting if you have tried cables both possible configurations then it appears, at a minimum, that the recovery circuit is not working.
https://stefancarey.zenfolio.com/p553178115/hF606202E#hf606202e
https://stefancarey.zenfolio.com/p553178115/hF6062034#hf6062034
Quote from: Stefan on February 12, 2021, 03:56:30 AM
2. Reverb cables to the reverb box, does it matter which they they go on?
Are the red and black cables on the reverb box (RCA connectors) reversible? That is, does the circuitry mind which way they are plugged in? Tried both ways and it does not seem to make any difference. (I think the term for this is 'polarity'.) Just want to be sure.
Each RCA cable has a signal and ground feeding signal to and from the reverb tank. Lets guess that the RED is sending signal IN (input on the reverb tank) and BLACK is sending signal (output on the reverb tank) back to the circuit in the amp. Drive circuit (I think is what it's called) sends to the input of the reverb tank and Recovery circuit (again this is what I call it) is the return signal from the output of the reverb tank.
Now as far as troubleshooting if you have tried cables both possible configurations then it appears, at a minimum, that the recovery circuit is not working.