Question:
Hey ya'll! I was working on repairing various cables today at church when one of the band members asked me if I'd be interested in helping him figure out what's wrong with his Mesa. Of course I had to say "Sure!" so he told me that whenever he uses it for around 35-40 minutes with standby on it will start to make a hum. He said he has taken it to the guitar shop a few times and they have charged him big bucks without being able to fix the problem. He's also replaced the tubes. I'm thinking it has to do with the transformer or shielding. I talked to a friend of mine from school and he said to start by taking a look at the shielding. I was just wondering if anyone on CGR knows how to remedy this. I don't know what model he owns because we didn't have enough time to talk over specifics but he's gonna drop it off at church and I'm going to pick it up, so I'll know more then.
Answer:
When you say standby on - do you mean the amp is in the standby mode, or operation/playing mode?
It sounds like a heat up problem; could be due to a faulty component, or possibly a bad solder joint. Usually its solid state devices like transistors that cause heat-up problems...tubes maybe can do that too, but they have been changed. A very common problem with amps is the input jack's solder joints getting broken from the cable getting yanked on, tripped over, etc. Boogies are somewhat upscale amps, they may have the input jacks mounted to the chassis with wire leads to the pcb. I had an old red knob Fender like that with a similar problem - ended up being the wire lead; it had been bent back and forth a couple times from previous repairs, and it was only hanging on by a thread.
Let it heat up - when the problem begins, bang on the amp a bit and see if that "fixes" it, if so its probably a bad solder joint.
Answer:
Alright, will do. Thanks again for all your help.
Answer:
My Boogie did something similar a while back - it ended up being the phase inverter preamp tube needing to be replaced.
Nate