So...
Lets concentrate on the right hand part of the circuit. Opamp IC503 is configured as a comparator with hysteresis (via R538) and so it should switch very cleanly.
It is unusual to get faults in such low power circuitry... and so I'm wondering if there is an issue with a noisy rail (such as the -/12 volts supplies from Q801 and Q802).
They should be checked with a scope to make sure they are good.
A noisy rail would also account for there seeming to be a problem on both sides of the circuit.
If you haven't a scope then the quickest way to eliminate stuff is just to replace it. That would be C805/6/7/8/9 and 10.
If the circuit still wasn't right, then at least we have eliminated stuff that would have needed a scope check.
Another good check would be to remove Q532 and fit a 220k preset between C and E and then check the operation of the comparator manually.
Lots we can do, but you need a few common parts and test equipment to make a quick diagnosis.
Lets concentrate on the right hand part of the circuit. Opamp IC503 is configured as a comparator with hysteresis (via R538) and so it should switch very cleanly.
It is unusual to get faults in such low power circuitry... and so I'm wondering if there is an issue with a noisy rail (such as the -/12 volts supplies from Q801 and Q802).
They should be checked with a scope to make sure they are good.
A noisy rail would also account for there seeming to be a problem on both sides of the circuit.
If you haven't a scope then the quickest way to eliminate stuff is just to replace it. That would be C805/6/7/8/9 and 10.
If the circuit still wasn't right, then at least we have eliminated stuff that would have needed a scope check.
Another good check would be to remove Q532 and fit a 220k preset between C and E and then check the operation of the comparator manually.
Lots we can do, but you need a few common parts and test equipment to make a quick diagnosis.