Using power transistors near its maximum ratings requires very careful circuit design because any minor oscillation, cross-conduction or thermal runaway issue will kill them. On the other hand, these are very rugged devices and I remember seeing people saying that they were capable to use them with +-70V in a reliable way.
Also, your transistors may be fakes, that would explain the blow-up quite well. In case you don't know what I mean, search the forum for 'fakes', 'fake transistors', etc...
Also, your transistors may be fakes, that would explain the blow-up quite well. In case you don't know what I mean, search the forum for 'fakes', 'fake transistors', etc...
Of course the problem may be simply that the output stage bias currents has increased dramatically with the rail increase from 30V to 70V. Amplifiers with resistive input diff'l tails are particularly sensitive to such changes in supply - their operating currents would more than double sending the output stage bias through the roof!
Cheers,
Greg
Cheers,
Greg
I like anatech's clue, make sure the driver transistors are within spec. They need to be able to take the whole 140 volts as well. A driver breaks down, and it will take out the output transistors.
What is your load impedance, and how many of those MJ output transistors are there in the circuit?
What is your load impedance, and how many of those MJ output transistors are there in the circuit?
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