Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Marcus on May 26, 2012, 09:23:07 am
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I have a JCA 50 and it doesn't seem to have that much gain and the output seem too low for a 50 watt tube amp.These amps are supposed to have alot of gain. This one doen't. With the gain cranked and the volume dimed I can stand right in front of the amp. I changed all the valves and biased the power tubes to 35 ma. They were biased at 9 ma but there was no difference in volume. I poked around with my meter and didn't find any open or bad resistors. I haven't checked any voltages yet. I also haven't checked the OT but I doubt that is the ploblem(I know it could be though). One thing I did notice is the ground wire from the effects return is disconnected for some reason. Could this cause a problem if I'm not using the effects loop?
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Does the low output still sound like the amp should? Did you jump the effects loop with a patch cord?
I've only had one of these in the shop. It had low output, but sounded right. The output transformer was bad and I had to replace it.
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Check voltage is the first thing to do.
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Did you find the problem with the Jet City amp?