Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Toxophilite on March 22, 2015, 03:27:29 am
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I picked up a fender champion 600 reissue today for $10 cause it wasn't working (It did have a Telefunken 12At7 in V1 so that'll pay for the amp!)
It was also missing the back panel, handle and a 6V6 tube
Spent a lot of time pondering till I noticed that R10 a 470 ohm resistor on the 6V6 cathode was cooked(pretty hard to tell), tested it and it was open
Replaced it and the amp works now (I tried it very briefly) it does have a very slight hum when it is on with nothing plugged in
Should I replace and or check out the 22 / 450 bypass cap that goes around 470 ohm cathode resistor I replaced?
i don't have a good electrolytic cap tester
The amp is a 2006 so about 9 years old and not near;y as bulletproof looking as the old fenders, though kind of a cute looking amp
A burnt resistor makes me think "Why did the resistor burn??" :dontknow:
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According to the voltage on the schematic, that 6V6 is running very hot. 22v across that 470Ω resistor means 47mA is flowing thru the resistor and the tube. That resistor is dissipating 1W anytime the amp is on. It's supposed to get hot. I would use a 5W resistor instead of the stock 2 watter.
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Good idear. I'll pick one up when I pickup my LEDs!
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the hum is something all these champion600 amps have.
an easy fix (but will not make the hum disappear completely) is to unscrew the side of the OT closest to the PT and then pivot it away from the PT. mark where it goes and make a new hole for a screw there.
the way to make it completely silent is with DC heaters. i tried it with an external DC supply and it was dead silent. even with the volume all the way up.
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Thanks!
I popped a 470 ohm 5 watt sandbox fuse in this amp and gave to my brother as he loves rocking out at reasonable levels..For what it is an excellent amp for power tube distortion at reasonable levels
I'm tempted to build one now!