Hi folks!
I have here a failing PM-53 with large DC offset at output. One of the chanels drives a couple of volts to the output. I have desoldered and ckecked all transistors past Q702/703, checked resistors, all OK.
Also, the other chanel sings OK, offset and bias are all OK.
Now, with desoldered components, measuring the voltages arround Q702 indicates, that the transistor is not operating. But, I can pull bassis down to ground with 10k resistor and get +38V on collector, instead of initial -41 Volts.
Does this looks like AN7062 is not driving Q702 properly? I can also manualy manipulate operation of Q702 by pulling (via 10k resistor) pins 4,5,6,7 to the ground! I have not tried to manipulate the other side, too risky to damage output trannies.
Floating voltage at pin 8 (desoldered) is arround +38V.
Thank you for answers!
I have here a failing PM-53 with large DC offset at output. One of the chanels drives a couple of volts to the output. I have desoldered and ckecked all transistors past Q702/703, checked resistors, all OK.
Also, the other chanel sings OK, offset and bias are all OK.
Now, with desoldered components, measuring the voltages arround Q702 indicates, that the transistor is not operating. But, I can pull bassis down to ground with 10k resistor and get +38V on collector, instead of initial -41 Volts.
Does this looks like AN7062 is not driving Q702 properly? I can also manualy manipulate operation of Q702 by pulling (via 10k resistor) pins 4,5,6,7 to the ground! I have not tried to manipulate the other side, too risky to damage output trannies.
Floating voltage at pin 8 (desoldered) is arround +38V.
Thank you for answers!