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Post subject: late 60's silver super reverb power?
Posted: Wed Jun 24, 2009 7:51 am
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I have a late 60's silver face Super Reverb. It powers up but after about 40 seconds the fuse blows and the rectifier tube snaps. If I take out the amp tubes, still blows. If I take out the power tubes, still blows. I replaced the rectifier tube, it still blew the fuse. I think these are the original filter caps. Where do I start?


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Posted: Wed Jun 24, 2009 9:46 am
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Power supply.


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Posted: Thu Jun 25, 2009 7:59 am
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Last edited by tinker tech on Wed Jul 29, 2009 11:02 am, edited 1 time in total.

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Post subject: Super Reverb power
Posted: Wed Jul 08, 2009 11:17 pm
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Yeah Catj, power supply would be the first suspect, and a visual inspection is very helpful ! IMHO the filter caps need to be checked,as do the power resistors. A current limiter would be useful, if the problem is not immediately evident, and a voltage or pop-test must be run over the unit. Did this happen all of a sudden? Or did you notice other degrading symptoms leading up to this condition? Art


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Posted: Thu Jul 09, 2009 3:59 am
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I have ordered new filter caps for it, a couple are back ordered. Visually the unit looks OK. No burned or melted components. No burned wiring or exposed metal. The unit was a relatives who had not used it in awhile and doesn't remember if the problem was there the last time he used it. there is a definite short in the rectifier tube after being on for about 20 seconds.


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Post subject: Super Reverb power
Posted: Thu Jul 09, 2009 8:17 pm
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Hi Catj, The filter caps are a good place to start. Have you worked on amps before this? These amps can store dangerous voltages even in worn out caps that must be discharged before you go poking around the inside of the chassis! NO FOOLIN' MAN ! Have you inspected the cap board under the cap pan? You'll need to check the resistors(4), the insulated wires leading back into the chassis, and the filter cap leads running under the board with a multi meter. If all checks out okay, the filter swap can be done without having to remove the cap board. I'd suggest you draw a sketch of the existing cap board so the installation of parts are not left to memory. Just a couple of questions : which circuit is this amp? (ie. AB763, AB568, or AA1069) ; does your amp stay on for 20 seconds, then actually blow the rectifier tube then the main fuse? Good Luck Art


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Posted: Fri Jul 10, 2009 4:01 am
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I have worked on amps and other electronics before. (If you want to see electric chair voltages, check out an old Barco 808 projector!!) I am not sure about which circuit. How can I tell? Yes, the amp comes on, the tube heats up then starts to spark at the base and the fuse blows. (This is with just the rectifier tube in place without the standby being turned on.) By the way, thanks to everyone who has replied so far, i really appreciate it.


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Post subject: Super-power
Posted: Sat Jul 11, 2009 11:17 pm
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Hey Catj, I apologize for asking about the circuit. You said it was a late '60's Silver Face. Yeah power supply! You'll have to get out the meter and check the AC to the rectifier,filaments,and bias supplies all the way down the line. Then the B+ voltage right down the chain. Hope you have a current limiter. Have you pulled and tested the filter caps and the bias cap? Yeah , guess you already checked the power amp section for failures, OT, and speakers. With some luck you'll just find a shorted filter cap. Wait a minute, did you say this occurs in the standby position? or not?Art


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Posted: Mon Jul 13, 2009 8:46 am
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The short and blown fuse occur with the standby switch in the off position.


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Post subject: Amp power problems.
Posted: Mon Jul 13, 2009 9:56 am
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Sounds like it is arcing on the socket at the base of the tube? Once that condition starts its new tube socket time. Have you tried a new rectifier tube in that socket to make sure its not the tube? -Ron


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Posted: Mon Jul 13, 2009 10:17 am
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Last edited by tinker tech on Wed Jul 29, 2009 11:03 am, edited 1 time in total.

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Posted: Mon Jul 13, 2009 10:33 pm
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Yeah, the 70-550 caps seem to be the source of the problem. But now you'll want to check that rectifier socket as posted above.


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