Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: matt mincer on March 12, 2018, 02:04:21 pm
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Hey All,
I have a Super Champ that's got an odd problem. The screen grid resistor (R79) burns up intermittently. I'll replace it, check everything and it'll work again for a few weeks. The kicker is, I've actually seen it happen. I cut the old one out and used jumpers to put one in for testing. At some point, it started smoking and burning so I cut the power. When I turned it back on, it was fine again. The voltages to the resistor are fine. The bias voltage is fine. Well, I say that but I haven't been able to test voltages while it's smoking. Does anyone have any ideas? I'm thinking I have a shorted tube but my tester is down so I can't check it.
Thanks
Matt
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Maybe you need a fresh set of 6V6s in the amp. Maybe replace the resistor with a 3W metal oxide resistor or maybe even a 5 or 10 watt resistor. Or maybe C40 is acting up occasionally. My first bet would be the tubes.
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:laugh: you keyboard better than me :think1:
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I reluctantly worked on a Super Champ X2 recently.
I consider myself lucky after removing and replacing the board approximately 10 times due to experimentation, and not breaking any critical parts.
I was sort of frustrated with the time and energy I put into that amp, I could have put a nice Princeton in the Chanp chassis and have a cool amp.
So that is what I am doing now is fitting a Princeton into a Champ as a surprise that he may not get for free, more like $1300.
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bad solder: check for a bad solder at tubes sockets
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I put some known good tubes in and let it cook overnight. So far, so good.
Thanks for all the tips.
Matt