How to diagnose 50+ Caliber reverb tank

Pre Recto days. Boogie modified Fenders, Mark I-IV, Dual Calibers, etc

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Mark II
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How to diagnose 50+ Caliber reverb tank

Post by primerib » Mon Oct 15, 2018 6:01 pm

So the heads have the reverb tank installed within the chassis. And my reverb no longer works. It is hardwired. So does anyone have recommendations on how to test if the tank is the problem and not something in the circuit?


Mark III
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Re: How to diagnose 50+ Caliber reverb tank

Post by woodbutcher65 » Tue Oct 16, 2018 8:02 pm

Tubes, tank, cables. ANY could be bad and causing the reverb to not work. Of course in that case, the cables are internal and probably not at fault.

So, bad reverb driver or recovery tube, or bad reverb tank.

Got spare preamp tubes? Put them in and see if reverb comes back.

If not, a bad tank is most likely.

There's not much else to go wrong. The only active components in the reverb system are the tanks and the drive and recovery tube stages. The rest is passive components that probably won't ever go bad.

The internal small tank frankly sucks anyway. I say you should do to it what I did to the one in my studio 22.

That being....

Yank the internal tank out and throw it in the trash. Drill two holes in the chassis and run input and output RCA jacks for the reverb system. (Be sure to use isolation washers on both RCA chassis mount jacks.) Order a complete reverb tank kit for a Mark III combo amp from Mesa, including the reverb cables and reverb bag.

Don't drill the holes for the new jacks until you've done the reverb tank installation in the chassis. That way you know where the jacks can be and have the cables reach.

Putting a REAL reverb tank in a studio 22 or 50 cal. is a huge upgrade. And not a very expensive one.

Now, you can improve the cooling in the chassis now that the internal reverb tank is gone. Obtain a 2" 12 volt DC fan with screws and install that fan on the vent hole section where the reverb tank used to be. For a power supply, get a 12 volt wall wart and take the plastic housing off it. Extract the circuit board, remove the AC power cord and install some wires to lead to the switched AC power in the amp between the power switch and the input power leads, and secure the DC power board wherever makes sense to you. Just lay down a big thick blob of hot melt adhesive, lay the board in it, and call it a day. That'll hold until somebody pries it out.

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