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Why do reverb tanks die?

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  • Why do reverb tanks die?

    I've had tanks that stopped working because a spring broke, or pulled out of the transducer thing, or the leads from the coil broke, but sometimes I have a tank where the DC resistance is good for input and output, the springs are where they are supposed to be, but the tank doesn't work, or maybe just gives a very weak reverb. Right now have this problem with a Sunn Alpha that used an O.C. Electronics folded line type 56. What's the deal?

  • #2
    Well there is the little ferrite bead on the long spring's tail, it sits centered in the gap in the little laminations. If that breaks away, no workie.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      The most common issue I see is broken wires connecting the coils to the connectors.
      Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
      If you can't fix it, I probably can.

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      • #4
        I've had tanks where the output transducer reads good for resistance but the output is low and in each case there was a break in the winding that was barely making contact and failing in use. I rewind 220R output transducers with #42 gauge pickup wire. Fill the bobbin and then use superglue with Zip-Kicker to seal everything. I've never had one fail second time round.

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        • #5
          Originally posted by Enzo View Post
          Well there is the little ferrite bead on the long spring's tail, it sits centered in the gap in the little laminations.
          Especially as it's not a simple ferrite bead but a permanent magnet. Without a magnet the motor won't turn, the springs won't do the Twist and the generator won't produce an outpt signal.
          Last edited by Helmholtz; 10-18-2020, 06:59 PM.
          - Own Opinions Only -

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          • #6
            I've worked on quite a few amps, though I am not professional repair person. It seems every third amp has a broken reverb tank. It is almost always a broken little itty bitty wire on the transducer. I have heard that these can be repaired, but for $20 new replacement tank, I go for that option. Sometimes I luck out and there is a broken wire on the RCA jacks, which is an easy repair.

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            • #7
              Thanks for the replies. As an update, I was looking at this reverb tank from the Sunn and the ferrite magnets looked like they were in place. I took a little chance and gave the ends of the springs some back and forth rotation. Reverb started working. Wiggled the wires around inside the tank to see if there was a break, reverb kept working. Mounted tank in amp and put it back together, reverb stopped working. Tore it apart again, repeated same steps, reverb working. Carried it gently to the amp stand and it is still working, not going to mess with it anymore, at least for now. I have a love/hate thing with this amp. It'll probably be buried with me because I will never get it working solid enough to sell it to anyone. It does sound great, to me it nails the vintage tweed sound better than any other SS amp I have tried. Really hate how it is put together though.

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              • #8
                In my experience most of the time the problem is with open transducers. I just saw it on the last three (two from Twin and Princeton Reverb and one from a Marshall DSL100) and they all have the output open.
                Sometimes I repair them by extending a thin wire between the contact pin and the transformer wire that is soldered, but in these three it has not worked. The break must be internal.
                It´s a satisfaction to find a wire unsoldered from the RCA connector but it is less common, at least in my experience.

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                • #9
                  The ones I've seen were broken springs or those tiny wires from the amp being manhandled.
                  --Jim


                  He's like a new set of strings... he just needs to be stretched a bit.

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                  • #10
                    Those Accutronics red bobbins are a real source of problems - the coil winding breaks where it runs along the groove to the connector pin. I see a lot with this fault. When I get a green or black lead break it's my lucky day.

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                    • #11
                      Why do Reverb Tanks die? Too many breakable entities in that spring-loaded suspended structure with tension-loaded long springs, fragile wires, fragile magnetic assembly under spring tension, and all of that mounted to a transportable light to too-heavy amplifier or combo amp that in handling and transporting imposes horrific mechanical shock/abuse to the tank. They can only take so much before the weakest link quits. I'll always take a shot at repairing them....half the time, it's one or more of the wires between the In/out connectors to the tiny transformer at either end of the tank. If the wires are directly from the transformer, and not from pin-mounted connectors, when those wires break away at the exit from the transformer...rarely gets restored. Connector pins with the push-on connectors.....IDC connectors most often....they break off at that IDC joint. I normally solder the wires directly to the pins and they work until the next time a wire breaks. When it's the end of the springs where they attach to the suspended ferrite magnet that's broken free.......I replace the tank. Why do Reverb Tanks die? Because they can!
                      Logic is an organized way of going wrong with confidence

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                      • #12
                        REmember the old days? The AMpeg amps with the little lever in back to hold the springs steady for transport? Or the Fender Reverb unit with the push bar that does the same?
                        Education is what you're left with after you have forgotten what you have learned.

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                        • #13
                          Originally posted by Enzo View Post
                          REmember the old days? The AMpeg amps with the little lever in back to hold the springs steady for transport? Or the Fender Reverb unit with the push bar that does the same?
                          YES, indeed! I didn't bring that up, as we just don't find that option being used anymore, though there's the code in the Acutronics Part Number system for that. Those DID help alot in extending the life of a tank, providing the owners bothered to use the locking lever.
                          Logic is an organized way of going wrong with confidence

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                          • #14
                            Originally posted by Enzo View Post
                            REmember the old days? The AMpeg amps with the little lever in back to hold the springs steady for transport? Or the Fender Reverb unit with the push bar that does the same?
                            I was working on a Vox Beatle a while back and it had a weird long bolt with 'wing nut' head threaded in to the headshell bottom, going nowhere. Then I realized there was an extra hole in the bottom where if you threaded in that wingbolt, it would hang up the tank thus locking it up for transport. Very odd arrangement.
                            Originally posted by Enzo
                            I have a sign in my shop that says, "Never think up reasons not to check something."


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                            • #15
                              This looks like a good thread to pose my question. I have a reverb tank here that has dropped a spring. The little magnet is MISSING!! At first, I thought these are simply ferrite beads, but no, they are magnets. So, my question - where can I buy replacement magnets? Then, once I get a replacement magnet, is there a specific type of wire to use to install the new magnet? I would guess a wire that can stand some flexing?

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