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Post subject: buzz and excessive heat from a 1970 twin reverb
Posted: Thu Oct 20, 2016 3:48 pm
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How much heat is normal from the tubes of a twin reverb 1970. also has a buzz coming from the amp


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Post subject: Re: buzz and excessive heat from a 1970 twin reverb
Posted: Thu Oct 20, 2016 4:06 pm
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Joined: Wed Mar 31, 2010 12:48 am
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Tubes are always too hot to touch with unprotected fingers when the amp is on.

The buzz likely indicates any one of a number of issues (or a combination) such as open input jack, poor grounding of the primary power cable, failing filter caps, or a marginal tube.

When's the last time the amp was serviced?

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: buzz and excessive heat from a 1970 twin reverb
Posted: Thu Oct 20, 2016 4:46 pm
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All that's been done to it is power cord, resolder ground wire and clean reverb wire inputs. Cleaning inputs helped but buzzing came back the next time I used the amp..Same old tubes being used but sure seems to get hotter than I remembered. Thanks for your reply


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Post subject: Re: buzz and excessive heat from a 1970 twin reverb
Posted: Fri Oct 21, 2016 7:19 am
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Check the idle bias of those 6L6GC tubes. Please post results.

Thanks! And good luck! ;)


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Post subject: Re: buzz and excessive heat from a 1970 twin reverb
Posted: Tue Oct 25, 2016 1:56 am
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Buzz/ Hiss ;
Test must be made with nothing plug to the amp

1-Input jacks close contact to ground is often bad; it stay open or it is dirty.
2-Tubes's plate resistors could be noisy.
3- Unbalanced output tubes
4- Bad 12XX7 tube.

You write ; "All that's been done "
All done right ? Sure ?
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"Same old tubes being used but sure seems to get hotter than I remembered"

Check bias at each tube ; this will say if tubes are OK


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