Just thought I would share this with you.
I have built two amps using this power amp before with no issues, and I was surprised by the quality of the sound and stability of this circuit!
However in my latest project involving the K8060 I encountered a rather stark problem.
Knowing that I successfully built two of these before I rather foolishly and impatiently decided to skip the light bulb test.
I powered the transformer on and then smoke began billowing from the Darlington Power Transistors and R15 started to turn black.
By this point I thought right game over for this circuit by the looks of things. During this point in time I took the liberty of checking the voltage of the bias across R19 and found it to be 4.5mV, so I adjusted the bias trimmer RV1, however to my bemusement no matter what I changed the resistance to it had no effect on the bias of 4.5mV across R19…
After all this I came to this forum and read through quite a few posts which spoke of burnt out resistors and problematic bias voltage across R19. Yet when the problem was resolved in these posts the creator never reported back about what their solution to the problem was.
Well mine was rather embarrassing but I post it here in the hope that it will help others. I accidentally put the Darlington Power Transistors TIP142(T8) and TIP147(T7) the wrong way round, essentially swapping the two for one another.