Reverb tank troubleshooting

[Clarkey]

Hi folks, I have a (new) TAD RV-4AB3C1B reverb tank going into a Princeton Reverb 1164 new build and I'm struggling to troubleshoot a weird (lack of) reverb issue...

I'm pretty sure it's narrowed down to the tank - the driver circuit will drive a speaker and tapping the tank creates clangs.

Both transducers seem to be OK, with sensible d.c. resistances (2.6Ω & 205Ω) and interaction with the spring, as I can produce a 'clang' with either end of the tank connected to the PR's reverb recovery circuit. The low impedance transducer is significantly lower in volume but that seems to make sense, given the fewer windings.

The cables test OK and the reverb driver signal from the amp is reaching the tank's driving-end transducer. However, I see no signal on the other transducer - even with the input up at ~2 volts. I get the same results if I swap the leads to drive the tank 'from the other end', so I don't think it's a tank polarity issue.

So, the signal doesn't seem to get through the springs - it's almost as if the packing foam that dampers the spring vibrations is still in place and working at 100% effectiveness, though this has long gone.

Am I missing something obvious?
Best,
Keith

[sluckey]

Try one more thing before you order a replacement tank. Plug your guitar into the reverb return jack using adapters, or gator clip leads and a phone jack. It may be easier to just temporarily replace the phono jack with a phone jack. You should be able to play guitar through the amp (not loudly) and the reverb pot will act as a volume control. If this test passes then get another tank.

[Clarkey]

Try one more thing before you order a replacement tank. Plug your guitar into the reverb return jack using adapters, or gator clip leads and a phone jack. It may be easier to just temporarily replace the phono jack with a phone jack. You should be able to play guitar through the amp (not loudly) and the reverb pot will act as a volume control. If this test passes then get another tank.

Thanks for the response and suggestion. Test passed, so the problem is definitely isolated to the tank. I've ordered a new one and can do an autopsy on the failed unit later.

[Clarkey]

New reverb tank arrived but unfortunately, no change...

The reverb drive circuit will drive a speaker with reasonable volume, the recovery circuit will hum (loudly) from a finger-tip touch at the tank end of the cable and will amplify my guitar. Both tank transducers work, as they'll generate a clang if connected to the reverb recovery circuit.

I can trace a guitar signal to the tank's drive transducer connector with a 'scope but not a whisper arrives at the transducer at the other end of the spring.

Grounding seems to be as per spec, the amp's recovery circuit socket (reverb output - 'red') is grounded and this has continuity through to the tank's red transducer ground and chassis. The amp's reverb transformer seondary is grounded one side (black), whilst the hot (green) side goes to the hot connector on the reverb drive socket (reverb input - white).

This seems to defy logic - it's as if the tank springs have a gap in the middle... and no, I haven't left the transport packing foam in place! 

Any ideas much appreciated.

[sluckey]

The only thing left is the cables. Try some different cables and be sure they are connected properly. The send jack on the amp is connected to the reverb transformer. Be sure it is connected to the tank input jack. The tank input jack will read about 1Ω DCR and the output jack will read about 215Ω DCR. Use your ohm meter to determine which is which if it's not obvious.