11-10-2022, 06:02 PM
I'd pick a sine wave rather than a square wave.
Other than that, you know what we're all going to say: get the oscilloscope out and do some diagnosis. You might have to temporarily solder wires to the board if you can't operate it upside-down (or otherwise arrange physical access). Follow the signal through, find out where it disappears, decide if it is a playback or recording issue (make sure the erase/bias oscillator is working). Before doing any of that, make sure you understand how it works from the schematic. Shame the scan is a bit low-res - is that the best copy available?
Other than that, you know what we're all going to say: get the oscilloscope out and do some diagnosis. You might have to temporarily solder wires to the board if you can't operate it upside-down (or otherwise arrange physical access). Follow the signal through, find out where it disappears, decide if it is a playback or recording issue (make sure the erase/bias oscillator is working). Before doing any of that, make sure you understand how it works from the schematic. Shame the scan is a bit low-res - is that the best copy available?
