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Follow up to my earlier post. http://music-electronics-forum.com/t44766/
Power now seems pretty good, but still cuts out (goes silent for a second or two) at high volume. Finally found out that it is happening when it gets some vibration or mechanical shock. It happens when the head is sitting on the bass cab, but not if it is isolated from the vibration. It also happens if you pick up the head and set it back down somewhat roughly. I am suspecting a cracked solder joint, maybe on a FET or torroid/transformer, I think the heat sinks for FETs are supported only by the FETS themselves, so maybe a weak spot. I opened it up and did a (gentle) tap test of the larger physical components with a drumstick and was not able to reproduce the problem.
The headphone output does not cut out, so I believe the preamp section is good.
My next thought was to just inspect the solder joints of all the through hole devices, or maybe just reflow all the larger ones. Any other ideas?
Thanks,
Greg
schematics:
Power now seems pretty good, but still cuts out (goes silent for a second or two) at high volume. Finally found out that it is happening when it gets some vibration or mechanical shock. It happens when the head is sitting on the bass cab, but not if it is isolated from the vibration. It also happens if you pick up the head and set it back down somewhat roughly. I am suspecting a cracked solder joint, maybe on a FET or torroid/transformer, I think the heat sinks for FETs are supported only by the FETS themselves, so maybe a weak spot. I opened it up and did a (gentle) tap test of the larger physical components with a drumstick and was not able to reproduce the problem.
The headphone output does not cut out, so I believe the preamp section is good.
My next thought was to just inspect the solder joints of all the through hole devices, or maybe just reflow all the larger ones. Any other ideas?
Thanks,
Greg
schematics:
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