Hi everyone.
A question.
I am repairing a Nakamichi PA-7E II, where one output is shorted ( 2SC3856 ) and the 20 watt resistor in the startup delay is dead.
Everything else is okay. Nothing lookes burned. All emittor resistors are okay, and the amplifier plays nicely on the drivers only.
Sometimes I've heard people say you need to replace all output transistors regardless, because the rest could be "half bad" (hotspots?).
It there any truth to this?
I think what happened is this:
When the output died, it drew a lot of current. This pulled down the transformer, which made the relay in the startup delay disconnect, killing the 20 watt resistor,
since the full current had to pass through it.
Therefore the rest of the transistors might not have been stressed. All other components are good, without any discoloring
Any oppinions?
I do have a few 2SC3856 somewhere. Otherwise all outputs get replaced by NJW0281/0302
Thanks in advance
/Jørgen
A question.
I am repairing a Nakamichi PA-7E II, where one output is shorted ( 2SC3856 ) and the 20 watt resistor in the startup delay is dead.
Everything else is okay. Nothing lookes burned. All emittor resistors are okay, and the amplifier plays nicely on the drivers only.
Sometimes I've heard people say you need to replace all output transistors regardless, because the rest could be "half bad" (hotspots?).
It there any truth to this?
I think what happened is this:
When the output died, it drew a lot of current. This pulled down the transformer, which made the relay in the startup delay disconnect, killing the 20 watt resistor,
since the full current had to pass through it.
Therefore the rest of the transistors might not have been stressed. All other components are good, without any discoloring
Any oppinions?
I do have a few 2SC3856 somewhere. Otherwise all outputs get replaced by NJW0281/0302
Thanks in advance
/Jørgen