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PostPosted: Wed Nov 20, 2019 10:25 pm 
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Joined: Wed Jul 12, 2017 6:11 pm
Posts: 8
Hello,

I have successfully built the Trinity Tweed Deluxe amp but it recently started having an issue with hum. I probed around inside the chassis and noticed that the hum is reduced when the shield from the signal cable going from pin 2 of V2 touches the middle lug of the normal volume pot (the layout indicates this shield should only be attached to the outside lug). At the moment this signal wire is floating over the board from V2 to the volume control. Should this wire be routed under the tag board and held close to the chassis? Will this reduce the hum I'm hearing?

Thanks for any and all help/advice!


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PostPosted: Thu Nov 21, 2019 2:14 am 
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Joined: Sat Dec 04, 2010 3:42 pm
Posts: 500
Location: Qualicum Beach, BC
If grounding the middle lug of the normal volume pot reduces the hum, that indicates a problem with the normal channel preamp. Check all the solder joints on the grounds of the input jacks and the grounds on the circuit board. Could be one of them was questionable and now has worked itself loose. There is a chance V1 has gone bad, too. If you have another 12AX7, or any tube in the 12A_7 family, you can try changing V1 and see if that makes any difference.

A shielded cable running under the board wouldn't be quieter than one running over the board. Anyway, it wouldn't suddenly start causing hum in an amp that has been working well. As long as the shield is connected to ground at only one end and it's insulated from ground at the other end.


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PostPosted: Thu Nov 21, 2019 10:56 am 
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Joined: Wed Jul 12, 2017 6:11 pm
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Thanks for the response Mitch. I'll try what you suggested.

Thanks


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