Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ndross475 on March 29, 2019, 10:16:11 pm
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So I was looking into the 1974x and saw a open box from an online retailer "deeply discounted" so I pulled the trigger... Good news the amp arrived today with a minor dent on the rear lower corner.... I could live with that for the discount...
Bad news, amp was DOA, Rectifier and V5 EL84 lit up, the rest were dark... Shut it down and replaced all the tubes... Amp worked, sounds amazing...at least to me.... Then no sound, problem comes back V5 and Rectifier lit, the rest of the tubes are dark. Shut it down, rolled some tubes and it worked again and while playing it just quit same issue... So its an intermittent problem. The worst kind.
I want to keep the amp, I could return it but would have to buy a new one, cost prohibitive, so I want to chase this for a minute, or may just run it to my tech on Monday...
Any ideas what my be causing this or where I should start looking? Layout and schematic are the same pretty much as those in the Hoffman Library. They just moved the can cap and fuses but the wiring is the same...
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Probably an open filament wire between V5 and V4. Look for a broken wire or bad solder joint on V5 and/or V4 socket.
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Sluckey you were dead on... I ended up taking it to my tech... as it was still in the return window.... 5 min repair. Heater wire on V5... tinned but not soldered well from the factory... Thanks....