Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: groovtubin on January 25, 2024, 11:49:37 pm
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Picked up one for $150 from a friend, in VERY good condition.... Was getting @ 49 volts at grids..... tried biasing per some utube guys way X the TUBE FUSE.... MISTAKE, was getting the full B+ ( 480) X the tube fuse, ( tht it had been modified!) even tho the AMP was playing FINE altho HOT HOT HOT.... tried RAISING NEGATIVE voltage n the bias pot FELL apart it was gone alredi! Pulled board drilled hole for a very nice 10K pot that fit right beside the PS Board, The 110 ohm resistor for cathode bias fell OUT on one side when i pulled board upside down 4 repair ! Repaired that wired up the bias pot ran a 27K vs (22k) Its maxed OUT at 52 volts but sounds GREAT n running VERY VERY cool......n sounds VERY good n VERY warm even on SS setting, ( wasnt B4 more metally lol) Im PULLING the rectifier tube it sounds AWSM in SS mode now FAR better than B4! Bias was just all amuck...n NO wonder the guy who had it b4 me was running in Tube rectifier mode lowering B+ to 423 vs 480 SS! :) Tryg ta SAVED the tubes lol....