Hi there,
I'm a little bit puzzled with my pioneer as when I check one side of the amp with 1khz sine at around 10W at 4 Ohm I will get this picture on my scope.
I checked the power supply (voltage is not breaking down), re soldered the pcb adjusted the idling current and check for 0V at the output. All Transistors, R's and C's are fine. I can hear a noise on the board when the oscillating begins.
How shall I start the repair? Just by changing all Diodes and Transistors and then all R's?
Many thnaks for reading,
Oliver
I'm a little bit puzzled with my pioneer as when I check one side of the amp with 1khz sine at around 10W at 4 Ohm I will get this picture on my scope.
I checked the power supply (voltage is not breaking down), re soldered the pcb adjusted the idling current and check for 0V at the output. All Transistors, R's and C's are fine. I can hear a noise on the board when the oscillating begins.
How shall I start the repair? Just by changing all Diodes and Transistors and then all R's?
Many thnaks for reading,
Oliver
You think it can affect just the positive half wave? I would think a problem would affect both half waves.
If the unit still has its original electrolytic capacitors on the amplifier board, it could be worth changing these. Dried out decoupling capacitors may well be causing instability.
If the Zobel is not faulty, coil and resistor in this case, check the two 56pF caps on the driver transistors and the 470pF caps plus the 0.01uF caps across the diodes, they can ring.
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