Glad it's fixed. A few morales from this story:
1. be aware that a meter does not necessarily test what it says it is testing - 'continuity' may simply mean 'same potential at lowish impedance'.
2. always tell helpers the whole story - don't hide 'unimportant' details from them, like extra filters; you will recall I did ask you for a circuit diagram of exactly what you built
3. from time to time, go back and recheck your assumptions and deductions
4. if it doesn't work, then there is something wrong; the failure to work is not caused by little quantum gremlins playing tricks on you no matter how much it may look like this - you would be amazed how often this elementary truth gets overlooked
I learnt all this from over 40 years playing with electronics as a hobby, and over 20 years developing and supporting complex software as a career.
1. be aware that a meter does not necessarily test what it says it is testing - 'continuity' may simply mean 'same potential at lowish impedance'.
2. always tell helpers the whole story - don't hide 'unimportant' details from them, like extra filters; you will recall I did ask you for a circuit diagram of exactly what you built
3. from time to time, go back and recheck your assumptions and deductions
4. if it doesn't work, then there is something wrong; the failure to work is not caused by little quantum gremlins playing tricks on you no matter how much it may look like this - you would be amazed how often this elementary truth gets overlooked
I learnt all this from over 40 years playing with electronics as a hobby, and over 20 years developing and supporting complex software as a career.
DF96: Thanks again. Not only I fixed the problem but I got some valuable knowledge out of it. The fact that the multimeter may be indicating same potential at low impedances when it beeps is fundamental.
Understand that I did not mention the line level filter since I had removed it from the circuit to rule out it being the culprit. When I found the beeping I thought: channels are mixed without the filter in the circuit so the problem is in the opamps.
Without your indications I would have always equalled beeping to channels mixed and would not have bothered to test again with a signal on the plug-in board. I would have been stuck.
Passing on your long time knowledge to others is praiseworthy. More so when it takes some valuable time to make sense of the fragmented information that those who, like me, have no electronic training or knowledge are able to provide.
Understand that I did not mention the line level filter since I had removed it from the circuit to rule out it being the culprit. When I found the beeping I thought: channels are mixed without the filter in the circuit so the problem is in the opamps.
Without your indications I would have always equalled beeping to channels mixed and would not have bothered to test again with a signal on the plug-in board. I would have been stuck.
Passing on your long time knowledge to others is praiseworthy. More so when it takes some valuable time to make sense of the fragmented information that those who, like me, have no electronic training or knowledge are able to provide.
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