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November 26, 2021, 03:26:13 PM

Author Topic: Have to adjust hum pot after touching 2A3 tube  (Read 501 times)

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Offline jerryZ

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Have to adjust hum pot after touching 2A3 tube
« on: May 21, 2021, 06:32:19 PM »
I found today that after I touched the right 2A3 tube and changed it position slightly,  I can hear the hum noise from the right speaker, the hum pot had to be re-adjusted to bring down the noise.
Not a big deal but just wondering if it is really that sensitive? I had the hum pot adjusted before and both channel were very quiet.

Thanks

BTW, mine is version 1, I built it back in 2013, have been in love with it since..


Offline Paul Joppa

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Re: Have to adjust hum pot after touching 2A3 tube
« Reply #1 on: May 21, 2021, 06:49:44 PM »
The socket contacts are not perfect, and a slight movement will make a slight change in the contact resistance. If you have not cleaned the tube pins and socket contacts lately, that's probably what happened.
Paul Joppa

Offline jerryZ

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Re: Have to adjust hum pot after touching 2A3 tube
« Reply #2 on: May 22, 2021, 05:41:04 AM »
The socket contacts are not perfect, and a slight movement will make a slight change in the contact resistance. If you have not cleaned the tube pins and socket contacts lately, that's probably what happened.

Thanks Paul, I should clean the pins and sockets, it has been in service for 8 years..

Offline Doc B.

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Re: Have to adjust hum pot after touching 2A3 tube
« Reply #3 on: May 22, 2021, 05:53:33 AM »
Exercise the hum pot a bit too, by turning it back and forth several times. Then reset it to the point of lowest hum.
Dan "Doc B." Schmalle
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Offline johnsonad

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Re: Have to adjust hum pot after touching 2A3 tube
« Reply #4 on: May 22, 2021, 08:41:03 AM »
Great advice as always DocB.  I do this with the cleaning of the RCA's semiannually and removing and reinserting the tubes a couple of times. 
Aaron Johnson