Hi folks!
I'm trying to find fault in an old Yamaha bass amp from the very early 80s, but I'm struggling a bit because of the fact that the fault is intermittent, sometimes instantly blowing the two 4 amp fuses on the main circuit board for the amp (secondary power side), sometimes working fine for extended periods.
I've disconnected everything I can, tested as much as I can with a meter.
I think I could probably find the fault quite easily if I could just power the board and trace it (I have the schematic), but obviously I can't do that because the fuses instantly blow when they do blow.....otherwise all is fine.
There is no short (no continuity) between B+ and B- anywhere on the board.
Does anyone have some good advice on how best to proceed, without unsoldering every single component and testing it?
P.S. This amp has worked fine for 20+ years. This first started recently when the terminal on the speaker frame broke, and the speaker wires shorted, blowing the fuses for the first time.
I'm trying to find fault in an old Yamaha bass amp from the very early 80s, but I'm struggling a bit because of the fact that the fault is intermittent, sometimes instantly blowing the two 4 amp fuses on the main circuit board for the amp (secondary power side), sometimes working fine for extended periods.
I've disconnected everything I can, tested as much as I can with a meter.
I think I could probably find the fault quite easily if I could just power the board and trace it (I have the schematic), but obviously I can't do that because the fuses instantly blow when they do blow.....otherwise all is fine.
There is no short (no continuity) between B+ and B- anywhere on the board.
Does anyone have some good advice on how best to proceed, without unsoldering every single component and testing it?
P.S. This amp has worked fine for 20+ years. This first started recently when the terminal on the speaker frame broke, and the speaker wires shorted, blowing the fuses for the first time.
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