Have to adjust hum pot after touching 2A3 tube

jerryZ · 3406

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Offline jerryZ

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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..




Online Paul Joppa

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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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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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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
Former President For Life
Bottlehead Corp.


Offline johnsonad

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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