Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tiny_Daddy on December 24, 2010, 08:35:09 pm
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Got a Alamo Capri, the one with a power transformer. The owner got it when he was 10 and said to soup it up some. So that means add a filament transformer, make a Gibson GA-5 / Hoffman Schedule 40!!! I used a bridge rectifier with the original power transformer, which was also powering the filaments, poor thing. Now it's just a plate transformer, supplying 230V under load. Connected a tone control to the top of the volume pot and away we go, works great. One other mod: add a 1 1/2 inch aluminum channel to the edge of the chassis, overlapped 1/4 inch. This stiffens things up and adds room for filter caps and a fuse holder. Filter caps are 250V because B+ never goes over 246V. EL84 data sheet (JJ) suggests cathode resistor = 135 ohms so I used two 270 ohm in parallel.