I was repairing an amplifier (classic with IRS21844 and drivers in Emitter-follower configuration).
After successfully repairing the power supply, I realized that a myriad of other faults were present, including 2 operational (tl072) and I preferred to replace them all together with all 4 regulators.
What amazed me is to see so many faults in a single amplifier, in fact I also found the drivers (pnp + npn) that take care of driving the output mosfets (KTA1715 + KTC2814), as well as having to rebuild the entire driver board.
They are almost impossible to find, so I decided to carry out tests with BD139 + BD140, but since I wasn't sure, I went there with caution.
My test was to try charging the transistors with only 1 mosfet per bank and it worked fine.
Then I installed all the mosfets, 4 for each bank, for a total of 8 mosfets for each output stage (there are only 2 output stages), and surprisingly, the amplifier worked beautifully.
There are no anomalous heating, neither on mosfets, nor on BD139 - 140.
Everything works perfectly, and the switching frequency is 102khz with 14.2 volts of battery.
I wanted to share this experience with you.
After successfully repairing the power supply, I realized that a myriad of other faults were present, including 2 operational (tl072) and I preferred to replace them all together with all 4 regulators.
What amazed me is to see so many faults in a single amplifier, in fact I also found the drivers (pnp + npn) that take care of driving the output mosfets (KTA1715 + KTC2814), as well as having to rebuild the entire driver board.
They are almost impossible to find, so I decided to carry out tests with BD139 + BD140, but since I wasn't sure, I went there with caution.
My test was to try charging the transistors with only 1 mosfet per bank and it worked fine.
Then I installed all the mosfets, 4 for each bank, for a total of 8 mosfets for each output stage (there are only 2 output stages), and surprisingly, the amplifier worked beautifully.
There are no anomalous heating, neither on mosfets, nor on BD139 - 140.
Everything works perfectly, and the switching frequency is 102khz with 14.2 volts of battery.
I wanted to share this experience with you.