LOUD HUM on JTM45 Build

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LOUD HUM on JTM45 Build

Post by JeffOD » Wed Mar 31, 2021 7:00 am

Hi All -
I'm new here. Built a few things (5F6A and 5E3 and aborted KLD 5F6A). Just finished the ValveStorm JTM45.
Voltages seem OK with my Fluke87. But when I plug in the KT66's and put a speaker load on and turn on the Standby
switch, I get this super loud hum/buzz. When the KT66's are not installed, the filter caps charge. But when the KT66's are installed - the filter caps DO NOT charge. Hmmmm. Any ideas guys? I could take this to my Tech here in Northern NJ, but
I really want to fix this myself. I've been putting my best foot forward, learning all I can. Can you guys point me in the
right direction? Thanks in advance.

Jeff OD

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Re: LOUD HUM on JTM45 Build

Post by shakti » Mon May 03, 2021 4:04 pm

A loud buzz or hum is usually the sign of a faulty ground connection. I would go over the connections on the output tube sockets and make absolutely sure they are correct (easy to get the order slightly wrong so you end up with something grounded that shouldn’t be and so on). Also check all other connections that are supposed to be grounded, particularly the output (speaker) jacks.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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