I've had a quad 303 on the repair bench for a while. It had around Vsupply-1v on pin 5. First suspects: the output transistors. But, nothing wrong with them.
Next: drivers. Nothing wrong. Next: gain stage (feedback?) nothing wrong.
it drove me insane. Replaced all transistors and diodes in a wave of frustration. Cheaper then the time it'd cost measuring everything. Still the same problem.
finally it was R113, 82K. fully open. so indeed it was the feedback loop, but not the semi-conductors. No visible damage, but after replacing the amp works fine.
moral: it's not always the usual suspects.
Next: drivers. Nothing wrong. Next: gain stage (feedback?) nothing wrong.
it drove me insane. Replaced all transistors and diodes in a wave of frustration. Cheaper then the time it'd cost measuring everything. Still the same problem.
finally it was R113, 82K. fully open. so indeed it was the feedback loop, but not the semi-conductors. No visible damage, but after replacing the amp works fine.
moral: it's not always the usual suspects.
That must have been a really nasty cheap quality chinaripoff resistor!! I have never seen a feedback resistor go bad.
Unless quad made the feedback so that the resistors work near their rated wattage.
Unless quad made the feedback so that the resistors work near their rated wattage.
Actually dead carbon films have been found in Rotels occasionally, so it does happen. Not the greatest parts quality in the first place, I guess.
- Status
- Not open for further replies.