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Post subject: '79 Twin Reverb Reverb Unit
Posted: Thu Oct 15, 2009 7:16 pm
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I have a '79 Twin with a sensitive reverb unit. Sometimes I'll engage the switch and there's nothing except a very distant reverb. If I shake the amp, it eventually comes back in full. I suspect there is a funky spring inside the unit. Can this be repaired? If not, is it best to find a vintage reverb unit or simply replace with a new unit?


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Posted: Thu Oct 15, 2009 9:50 pm
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Hi Bert, still got that contact cleaner? I suspect a dirty RCA connection or tube socket. It's an outside bet that there is a loose connection in the tank. Try spraying some cleaner on each RCA plug and rotate as you replace them in their respective jacks. So you'll have to carefully remove the tank to get at those plugs. Then I'd remove V3&V4, give them a shot, and replace. It doesn't take much of the cleaner. It's not a bad idea to use a sharpie to put a reference mark on the tube glass and the shield retainer, to help align the tube pins for replacement. I would remove the footswitch to test the reverb, but those plugs could use the cleaner too. The footswitch can also be opened up and the switches cleaned unless they are sealed units. You could hit all the tube pins with the spray, as long as you're at it. The reverb control pot is the only other part that could use cleaning. But don't open the chassis unless you know how to discharge the filter caps!!!! Hope this helps. ART

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Posted: Sat Oct 17, 2009 12:58 pm
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Cleaned the pins on all tubes and removed and cleaned all contact connections on the reverb tank. All seems to be working well with no cutting out, although the reverb still sounds a little distant compared to my 65 RI.


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Posted: Sat Oct 17, 2009 5:55 pm
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Alright Bert, good job. There's only two things I'd try before buying a new tank. Make sure V3 & V4 are good strong tubes first. Then you could try the Twin's tank with the Deluxe. These should both be the same type tank(accutronics#4AB3C1B). You can verify this by checking both tanks. However, if the Deluxe has say a #9AB3C1B, forget the comparison, that's a fuller and richer sounding tank. Good Luck! ART

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Posted: Wed Dec 16, 2009 6:19 am
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So my reverb finally crapped out in the 79 Twin. I tried the tank from my 65 RI and it did not work in the 1979 so I suspect I have an internal circuit problem which will require a trained tech.


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