Although I've got no white smoke and nothing has catastrophically failed - YET. I'm loathe to keep power on this for too long for measurements.
I only build these, I don't design them so any pointers as to which area I should target first with the meter would be much appreciated.
I only build these, I don't design them so any pointers as to which area I should target first with the meter would be much appreciated.
OK I've taken some readings ?
Now, if you recall, the LH amp seems OK and the RH amp is at fault.
To my novice brain I would suspect the op-amp.
On the working amp everything is stable and the ouput of the op-amp is a steady 0.19V.
On the faulty amp the output of the op-amp is unstable and seems to keep climbing to round the 3.5V mark. Differences in readings along a pcb trace are due to the voltages changing as I move the MM probe around.
Both PCBs are identical and the components are identical.
Now, if you recall, the LH amp seems OK and the RH amp is at fault.
To my novice brain I would suspect the op-amp.
On the working amp everything is stable and the ouput of the op-amp is a steady 0.19V.
On the faulty amp the output of the op-amp is unstable and seems to keep climbing to round the 3.5V mark. Differences in readings along a pcb trace are due to the voltages changing as I move the MM probe around.
Both PCBs are identical and the components are identical.
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Please check the voltage on the base of TR1 and TR3 for both channels and report the result edit: just noticed RichieBoy suggested replacing them.... based on the voltage differences you are seeing I'm suspicious of them... could also be a bad joint on R10 or R12 or possibly bad C11/C13.
Tony.
Tony.
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