How to test a Reverb Tank? (Furman RV-1)

Hi guys,

my friend brought me a Furman RV-1 to troubleshoot.

I've tested every stage and everything seems OK... but the reverb signal is very weak. Sounds almost like crosstalk.

What's the best procedure to test the Reverb Tank? I checked the DC resistance. 25 ohm at the Input and 200 ohm at the output.

Any thought?

Cheers

Note that there are different versions with quite different circuits. If you don't see an optocell in there, that's not the schem for it.

squarewave said:

Note that there are different versions with quite different circuits. If you don't see an optocell in there, that's not the schem for it.

Click to expand...

The schematic is correct. It’s the version with the vactrol.

elskardio said:

Hi guys,

my friend brought me a Furman RV-1 to troubleshoot.

I've tested every stage and everything seems OK... but the reverb signal is very weak. Sounds almost like crosstalk.

What's the best procedure to test the Reverb Tank? I checked the DC resistance. 25 ohm at the Input and 200 ohm at the output.

Any thought?

Click to expand...

Have you checked the spring is attached to both transducers and in one piece? A broben or disconnected spring is a very common fault of spring reverbs.

Check the foot switch jack. If broken it will short out the reverb signal. Scope the signal before and after R27.
Duke

Ok so I removed the reverb tank to inspect the spring and everything is in good condition.

It's like no signal goes thru the spring.

I have tested the driver and it's working great. But when I probe the return of the tank, I have no signal...

This puzzled me  ???

I'm not familiar with that particular model, but I have experienced that fault. Make sure the ground is connected at only the output, and check the tank to see the input is isolated from the tank chassis- the input jack is mounted with an insulator.

walter said:

I'm not familiar with that particular model, but I have experienced that fault. Make sure the ground is connected at only the output, and check the tank to see the input is isolated from the tank chassis- the input jack is mounted with an insulator.

Click to expand...

Not necessarily; all sorts of options are possible on Accutronics tanks, floating/grounded input or output are possible.

I did a lot of testing today. I've tested the different circuit stages again. Everything seems ok.

The reverb signal is weak and sounds filtered (no bass). I think I'll breadboard a simple driver and test the tank by itself.

just rattle the springs with your hand and see if it sounds like a thunder storm,

Broken connection inside the tank, from transducer to in/out jack. Look for open circuits there.

The mechanical connections inside reverb tanks can be delicate and break. These were generally inexpensive when in wide use, so often throw-aways. Good luck.

I second the advice to gently excite the spring with a pencil eraser of something not conductive. If you get a loud full bandwidth response check the send side, if low muffled output focus on the receiver end.

JR

abbey road d enfer said:

Not necessarily; all sorts of options are possible on Accutronics tanks, floating/grounded input or output are possible.

Click to expand...

Yes, this is my point. If the pan was ever replaced or if the cables to the pan have been repaired problems can occur if the correct configuration is not maintained.

rackmonkey said:

Broken connection inside the tank, from transducer to in/out jack. Look for open circuits there.

Click to expand...

The OP wrote "checked the DC resistance. 25 ohm at the Input and 200 ohm at the output." Doesn't look like open circuit to me...

I never miss anything, Abby. Just seeing if you're awake.  ;D