Have a BF vibrochamp aa764 with no output.
They had a 5u4c in place of the 5y3. The 6v6 was just about dead. upon opening the amp it was apparent it had never been worked on before.
Replacing the 25uf 25v caps and 470 bias resistor and the 10uf/25v cap an cobbling in a test OT The amp does work.
My thoughts are the 5u4 pushed the voltage up which stressed the already old caps which burnt up the 6v6 and took out the OT.. Is this correct?
Somewhere I was reading a company provided mods( a resistor on the power tube socket) would that be a screen resistor? which would have prevented some of the damage?
just pondering here
Thanks,
nosaj
They had a 5u4c in place of the 5y3. The 6v6 was just about dead. upon opening the amp it was apparent it had never been worked on before.
Replacing the 25uf 25v caps and 470 bias resistor and the 10uf/25v cap an cobbling in a test OT The amp does work.
My thoughts are the 5u4 pushed the voltage up which stressed the already old caps which burnt up the 6v6 and took out the OT.. Is this correct?
Somewhere I was reading a company provided mods( a resistor on the power tube socket) would that be a screen resistor? which would have prevented some of the damage?
just pondering here
Thanks,
nosaj
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