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Post subject: 1964 Twin Reverb Hum / Buzz
Posted: Sun Dec 26, 2010 7:21 pm
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Hobbyist
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Joined: Sun Dec 26, 2010 7:07 pm
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Just bought a really nice condition '64 Twin Reverb and after I got it home started noticing a hum / buzz once you turn the standby switch on. It isn't crazy loud or anything, but just enough to be annoying for recording. It is present when the volume is all the way down and it doesn't get louder at all when you turn the volume up. This is without any kind of cable or instrument plugged in. It does get a bit louder when you engage the reverb.

Don't remember it doing this in the store as i was thinking how quiet it was and the only noise I heard was just a little hissing when turned fully up.

Not sure how much hum or buzz is normal with these, but other vintage amps I have are pretty much dead quiet with the volume off and only hum or buzz as you increase volume.

It also makes a fairly loud popping noise when you turn the standby switch on as well.

Any ideas on what the issue might be would be greatly appreciated. Also not a tech or anything so I don't know too much about wiring, etc...

thx


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Post subject: Re: 1964 Twin Reverb Hum / Buzz
Posted: Sun Dec 26, 2010 8:02 pm
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Aspiring Musician
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Joined: Fri Dec 12, 2008 5:32 pm
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you probably need to adjust the hum balance pot


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Post subject: Re: 1964 Twin Reverb Hum / Buzz
Posted: Sun Dec 26, 2010 10:21 pm
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May also have dirty standby switch. Try a little contact cleaner made for switches & pots.


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Post subject: Re: 1964 Twin Reverb Hum / Buzz
Posted: Sun Dec 26, 2010 10:38 pm
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joncarr1979 wrote:
you probably need to adjust the hum balance pot


There is no "hum balance pot" on a 1964 Twin Reverb. That wasn't added until much later, during the silverface era.

More likely, the amp is ready for new filter and bias caps.

The audible 'pop' when switching from "standby" to "operate" is probably caused by arcing contacts within the switch itself. These become worn and pitted with age and the symptom will only grow worse in time, hazarding other components within the power supply and the output stage.

HTH

Arjay

_________________
"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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