Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Effects => Topic started by: luthierwnc on September 10, 2023, 03:42:42 pm
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Hi all, I got an older Blues Driver to mod with an aftermarket product. They shall remain nameless since they have no part in this fiasco.
I replaced the parts shotgun and it worked fine the first time. A couple days later it failed -- signal passed when it was off but nothing when engaged. I took it apart again and started testing for issues. When it was plugged in as I checked on a scope for signal I heard a soft tssssst and smelled a hint of burn smoke. Hate that smell. At any rate it is now dead.
I've since ordered another but want to make this a trial balloon for working on this type of circuit. Every fix-it blog and vid I've seen are for people who have used the wrong polarity or wrong voltage. My guess, and this is a guess, is that I dragged the PCB across the exposed edges of the aluminum box and shorted something inside. I'll tape those next time.
All of the diodes test fine. I checked all the resistors. Some are wildly out of spec but none were burned, dead shorts or open circuits. I don't know how to test FETs but will spend a little time on the net finding more. There is no sign of heat damage anywhere. Some traces have fresh solder for new components but a close look saw no overlap.
Any other ideas on how to trace the gremlin? Thanks for looking and wish me luck. Cheers, Skip