here are pictures of the two driver boards
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Any time that the transistors are off of the sink, you have to be very careful until you know that there is no fault that will cause the FETs to heat up. Even with no fault, sometimes the FETs (or other components) can heat up and fail. Sometimes it happens quickly and sometimes it takes several minutes for them to begin to overheat.
The other 1D and 2D transistors on the boards sometimes fail but it's not as common.
I've checked transistors in the circuit before and they checked open but after removing them, they appeared to be OK. I'd suggest replacing them. They run very hot. Generally, the board is discolored under those transistors because they operate at such high temperatures.
The other 1D and 2D transistors on the boards sometimes fail but it's not as common.
I've checked transistors in the circuit before and they checked open but after removing them, they appeared to be OK. I'd suggest replacing them. They run very hot. Generally, the board is discolored under those transistors because they operate at such high temperatures.
Does anyone have the part number for Q6/Q7? I see where one person substitutes a MPSA42 in to-92 package for more power handling. Is there a schematic of this circuit anywhere? Are these NPN transistors just used as switches?
Does the discoloration on D5/D6 on driver board mean anything? I guess I can take diodes off and check them.
Next I will install heat sink clips, and remove driver board and see if protect light goes out.
Does the discoloration on D5/D6 on driver board mean anything? I guess I can take diodes off and check them.
Next I will install heat sink clips, and remove driver board and see if protect light goes out.
MMBTA42
Virtually all of the transistors in the drive circuit for class D amps are used as switches.
I've never seen any problems with the diodes on that board.
There have been instances where one of the TL072s have failed but that generally caused 'no audio' instead of the amp going into protect.
Virtually all of the transistors in the drive circuit for class D amps are used as switches.
I've never seen any problems with the diodes on that board.
There have been instances where one of the TL072s have failed but that generally caused 'no audio' instead of the amp going into protect.
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