Bryston 4B amplifier has knocked out transistors

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ChRobin

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Bryston 4B amplifier has knocked out transistors
« on: 14 Oct 2020, 10:21 am »
Hello!
Problem.
The Bryston 4B amplifier has knocked out transistors MJL21193/MJL21194 in the output stage.
All supply voltages are normal, soft start is working.
If you change the blocks among themselves, then a working channel works both on the left side and on the right. The preamplifier board also works both in the left channel and in the right (with a working power amplifier block).
After replacing transistors - breakdown again.
Powered the faulty channel from the laboratory unit. With an increase in the supply voltage + - 60-70 V, a sharp increase in current consumption and strong heating.
Also, a serviceable channel, after switching on and the absence of a signal at the input, heats up significantly.
I ask for help, where to look?
I also want to know if it is possible to purchase matched pairs of output transistors  MJL21193/MJL21194, send an output stage board for repair, or receive such a board within a 20-year warranty from service support.
I would be glad to any advice and help.

James Tanner

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Re: Bryston 4B amplifier has knocked out transistors
« Reply #1 on: 14 Oct 2020, 10:36 am »
Hello!
Problem.
The Bryston 4B amplifier has knocked out transistors MJL21193/MJL21194 in the output stage.
All supply voltages are normal, soft start is working.
If you change the blocks among themselves, then a working channel works both on the left side and on the right. The preamplifier board also works both in the left channel and in the right (with a working power amplifier block).
After replacing transistors - breakdown again.
Powered the faulty channel from the laboratory unit. With an increase in the supply voltage + - 60-70 V, a sharp increase in current consumption and strong heating.
Also, a serviceable channel, after switching on and the absence of a signal at the input, heats up significantly.
I ask for help, where to look?
I also want to know if it is possible to purchase matched pairs of output transistors  MJL21193/MJL21194, send an output stage board for repair, or receive such a board within a 20-year warranty from service support.
I would be glad to any advice and help.

Hi

Please email Mike - mpickett@bryston.com

james

ChRobin

  • Newbie
  • Posts: 2
Re: Bryston 4B amplifier has knocked out transistors
« Reply #2 on: 14 Oct 2020, 11:02 am »
Thanks for the quick response!
Sent to Mike