# How do I test a Reverb tank?



## Gene Machine (Sep 22, 2007)

anyone know how I can test the reverb tank? I don't have a spare to swap out.


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## Granny Gremlin (Jun 3, 2016)

If it's Acutronics, the model number will give you the input and output impedance. Compare to the DCR measurement of tip to sleeve each of the in and out jacks. DCR should be 80-95% of the impedance spec (just like a speaker - an 8 ohm speaker will measure between 6 and 7.8 Ohms).

That just proves the transducers in there aren't shorted or open. Next visually inspect the springs for breaks or any other obvious signs of damage (connection of springs to transducer at each end). You can try putting it in another amp, but check the model number on the other amp's tank because if the in/out impedance isn't the same might not work even if not faulty (the Z on tanks varies greatly; much more so than with speakers)
.


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## nonreverb (Sep 19, 2006)

Typically with a reverb driven tank, it will be low on the transformer end 4 to 8 ohms ans 150 to 200 ohms on the receiving end.
Here's a little test to try if you're still having problems with the Ampeg. Connect a small speaker to the transformer side and see if the noise is present in the speaker.
Remember, the tube and transformer driver is essentially a small amplifier.


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## Granny Gremlin (Jun 3, 2016)

Unless it's solid state (driver or recovery circuit) and then the Z is wildly different from that of all tube amps. E.G. the tank from my TRaynor YVM-6 won't work in most other things. Sounds great in the YVM-6 tho. 

Don't assume, some makers did weird things sometimes; the part number will give you the exact specs for that tank. My Sunn heads have tube reverb drivers but solid state recovery amps for example.


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## mhammer (Nov 30, 2007)

Alternatively, if the tank is not installed, measure the AC voltage on the output and give the springs a little finger boing. If the tank iis okay at that end of things, you should measure a couple of millivolts or so.


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## nonreverb (Sep 19, 2006)

Granny Gremlin said:


> Unless it's solid state (driver or recovery circuit) and then the Z is wildly different from that of all tube amps. E.G. the tank from my TRaynor YVM-6 won't work in most other things. Sounds great in the YVM-6 tho.
> 
> Don't assume, some makers did weird things sometimes; the part number will give you the exact specs for that tank. My Sunn heads have tube reverb drivers but solid state recovery amps for example.


Hammond organs also have all tube reverb driver and receivers however, they don't use transformers to drive the tank. Their tanks are totally unusable in typical fenderesque reverb circuits.


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## Granny Gremlin (Jun 3, 2016)

1 example doesn't make me wrong. 

Here''s a fact, reverb tanks come in all these variations (and this is JUST acutronics):

* INPUT IMPEDANCE* 
Type 1 and 4 tanks: 
A = 8 Ohm
B = 150 Ohm
C = 200 Ohm
D = 250 Ohm
E = 600 Ohm
F = 1475 Ohm
Type 8 and 9:
A = 10 Ohm
B = 190 Ohm
C = 240 Ohm
D = 310 Ohm
E = 800 Ohm
F = 1925 Ohm

*OUTPUT IMPEDANCE* 
Type 1 and 4 tanks: 
A = 500 Ohm
B = 2250 Ohm
C = 10000 Ohm
Type 8 and 9:
A = 600 Ohm
B = 2575 Ohm
C = 12000 Ohm

And then multiply for the various permutations and combinations of the above.

The tank out of that Traynor I mentioned (higher Z in and out; don't recall exactly tho), did not work at all in my Garnet (all tube but no transformer; probably 8 in and 200 out standard thing, but nor sure - didn't check). I never said that they had to match the original exactly to 'work' in another amp, just that , since the diff between min and max Z among models is so large, it is possible it won't.


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## epis (Feb 25, 2012)

nonreverb said:


> Hammond organs also have all tube reverb driver and receivers however, they don't use transformers to drive the tank. Their tanks are totally unusable in typical fenderesque reverb circuits.


If you have some collecting dust or going to scrap, I would like to have it. I can make them work for transformer driven stage.


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## BGood (Feb 20, 2015)

Kick it


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## nonreverb (Sep 19, 2006)

epis said:


> If you have some collecting dust or going to scrap, I would like to have it. I can make them work for transformer driven stage.


They have pretty high input impedance Damir. Around 200 ohms.


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## epis (Feb 25, 2012)

nonreverb said:


> They have pretty high input impedance Damir. Around 200 ohms.


I know Rich, I rewind input coil to 8 ohms.
It's not worth it to do it on comercial basis because of work involved and price of new ones, but works for hobbyist like me.


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## nonreverb (Sep 19, 2006)

Wow...really? If you're doing that, you should be rewiring all those shitty Accutronics tanks with blown send coils...Had I saved them all, I could fill your house with them.


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## jb welder (Sep 14, 2010)

Granny Gremlin said:


> Compare to the DCR measurement of tip to sleeve each of the in and out jacks. DCR should be 80-95% of the impedance spec (just like a speaker - an 8 ohm speaker will measure between 6 and 7.8 Ohms).


This part is incorrect, the DC resistance is much lower than the impedance for reverb tanks. 
For example, typical fender BF tank input impedance is 8 ohm but measures about 1 ohm DC on your meter. The 2250 ohm output impedance will measure around 200 ohms DC resistance. 
There is a nice chart on page 4 of this pdf: https://www.amplifiedparts.com/site...ing_reverb_tanks_explained_and_compared_1.pdf

You did make me wonder why the huge difference when speakers are not so far off.


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## Granny Gremlin (Jun 3, 2016)

Interesting - thanks for the link.


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