bias transistor

[timwebb]

what would cause the biasing transistor blow on an amp?

[wahab]

too much current, wether it comes from the vas or
a failed current source, or even from the following stages,
drivers + power devices...
it can also be that it has too much voltage across his
emitter and collector, but by the time this happen,
the output devices would have blown well before, generally...

[timwebb]

could a bad driver cause this

[wahab]

without schematic, it s difficult to have a precise clue.....

[Andrew Eckhardt]

in usual circuits you'd need both + and - drivers shorting collector to base without the collector to emitter current shutting down the power supply very quickly. Pretty rare. Other than that you'd need very large currents coming out of the VAS.

[timwebb]

one of the drivers shorted just didnt blow. a resistor blew that connected them both. im going to change them and see what happens

[Andrew Eckhardt]

I'd proceed on that one with extreme caution. If you cooked one driver and the bias transistor, that fault current must have gone Edit: somewhere.