Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jim on September 10, 2022, 12:29:35 pm
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The normal channel is normal volume and clean. The power amp is working fine. Trading pre-amp tubes between channels shows the problem stays with the vibrato channel. There is a hair of distortion whenvibrato volume is 10 but volume is real low. Voltages on the tube socket look normal--235V on 1,6 and 1.6V on 3,8. I replaced the bypass caps on the cathodes. Funny thing is when I opened the chassis I founda 1/4 inch plug tip rolling around inside. Also reverb and trem works OK on the vibrato channel--not modded for both channels. How should I chase down the problem? Thanks, Jim
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I have a 65 Showman and ran into this same issue when I got it a few years ago. I was informed here by more experienced guys that this is somewhat normal due to the load of the vibrato circuit on that channel. On my showman, I need to be at like 6-7 on the volume to match 4 on the normal channel.
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Actually trem does not work but I can see the roach flashing. This volume is is super low barely audible. Jim
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Just to be clear, it’s a Bandmaster Reverb?
How about the V4 voltages? Including the grids.
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OK voltages are 231V 1,6; 0V on grids; 1.8V on cathodes. But when I simply touched pin 6 with the test lead there was the usual static and then the channel suddenly came alive. What did I do--should I remelt the solder and call it a day? I dont't understand. But I appreciate your insight. Jim
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Likely corrosion and fifty years of grime on the tube socket. Ill clean it up. Thanks!
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remelt the solder and ...
Do that not only for that part of the amp , but do a check on everything, is the amp old?