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Topic: Dead reverb in a fender twin |
Dan Beller-McKenna
From:
Durham, New Hampshire, USA
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Posted 13 Sep 2010 12:07 pm |
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The reverb has quit on my '78 135 watt fender twin. Hoping someone can suggest where to look for the culprit. Noticed a week ago it wasn't functioning. Then, at a gig Saturday night it started making progressively louder pops and sizzles as the amp warmed up. These were eliminated by turning the reverb level all the way down. I assumed that meant a bad tube. But when i replaced the reverb tube, although the noise was gone, I still had no reverb. "No reverb" means none in the signal as well as none when I jiggle the reverb pan. Any thoughts?
Thanks,
Dan
_________________
Durham, NH
dbmCk mUSIC
Last edited by Dan Beller-McKenna on 13 Sep 2010 1:10 pm; edited 1 time in total |
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Erv Niehaus
From:
Litchfield, MN, USA
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Posted 13 Sep 2010 12:48 pm
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| I'd check/clean the connections between the reverb and the amp. |
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Lee Warren
From:
Nashville, Tennessee, USA
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Posted 13 Sep 2010 1:03 pm
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Hi Dan,
If tube replacement and cable checking doesn't help, you might want to check inside the reverb tank itself.
The (tiny) wires that connect the trandsucers to the connectors on the tank chassis are prone to breakage.
Good luck!
Lee |
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Dan Beller-McKenna
From:
Durham, New Hampshire, USA
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Posted 13 Sep 2010 1:11 pm
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Sounds like a plan guys; I'll have a look at the wires.
Dan
Last edited by Dan Beller-McKenna on 13 Sep 2010 3:16 pm; edited 1 time in total |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 13 Sep 2010 2:44 pm
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The plastic molded RCA connectors are the first to go, then the tiny internal wires (usually the driver coil itself) in the tank itself. If it is the first it's a re-solder job. If it is the second you will need a new tank, which will cost around $30. You will need the model numbers stamped on the outside of the tank to order the correct replacement.
If you need to do so I suggest that you start with Antique Electronic Supply - 1-480-820-5411
more info can be found at http://www.accutronicsreverb.com/ |
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Mark Lavelle
From:
San Mateo, CA
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Posted 13 Sep 2010 3:41 pm Re: Dead reverb in a fender twin
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| Dan Beller-McKenna wrote: |
| ...started making progressively louder pops and sizzles as the amp warmed up. These were eliminated by turning the reverb level all the way down. I assumed that meant a bad tube. But when i replaced the reverb tube, although the noise was gone, I still had no reverb. |
There are actually two tubes in the reverb circuit: the 12AT7 (V3 on the AA270 schematic) and half of a 7025 (V4A). from your description it sounds more like the latter would be the problem (if it's a tube problem).
But your description sounds more like a failing tank, to me (more specifically, the return transducer becoming detached).
-- Mark
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http://www.harmonicappliances.com/ |
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Jim Pitman
From:
Waterbury Ctr. VT 05677 USA
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Posted 15 Sep 2010 8:49 am
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| If you are at all handy and have an ohmeter - measure back into the tank via the RCA jacks - It should read anywhere from 300 to 1200 ohms. If it's infinite than the coil or the small wire leading to the coil is broken. I rewound a coil once - not worth it. Buy a new tank. |
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Dan Beller-McKenna
From:
Durham, New Hampshire, USA
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Posted 17 Sep 2010 12:50 pm
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Well, turned out to be the cables--I think. I did pull out the pan and, as Dave and Mark suspected, the little wire tot he return jack was detached. Resoldering that did not fix the problem, however. Putting new rca cables in did the trick.
Thanks for the help folks.
Dan |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 17 Sep 2010 2:20 pm
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| You gotta love the easy fix! Glad it worked out at low cost and in short order for you, Dan. |
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