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hamid_1 · 28th May 2021, 3:24 pm

I'm guessing a bit here, but the one with the rewind LED lit and the end alarm sounding, could have a faulty tape end sensor or its associated circuitry. Unlike VHS, Betamax tapes have a foil strip at the beginning and the end. The end sensors are coils. When the foil passes by the pick-up coil, it changes the coil's inductance and that triggers the tape end sequence (the alarm sounds, then it rewinds after a few seconds).

As for the second one, it sounds like it has not detected the presence of a tape - there's a switch in the cassette compartment which may be dirty and not operating.

If the power supply was just dead before you repaired it, then it shouldn't have damaged anything. You can always unplug a board and swap it with the same one in the other machine, then see if the same fault has moved along with the board. If it does, then you know that board is faulty, otherwise it could be another board or something else like a motor, switch or sensor.

The C7 was a very complex machine. I believe it had 3 microprocessors in total. Tracing logic faults is rather difficult.

28th May 2021, 3:24 pm	#4
hamid_1 Heptode Join Date: Aug 2009 Location: High Wycombe, Bucks. UK. Posts: 811	Re: Bringing a Sony C7 Betamax back to life I'm guessing a bit here, but the one with the rewind LED lit and the end alarm sounding, could have a faulty tape end sensor or its associated circuitry. Unlike VHS, Betamax tapes have a foil strip at the beginning and the end. The end sensors are coils. When the foil passes by the pick-up coil, it changes the coil's inductance and that triggers the tape end sequence (the alarm sounds, then it rewinds after a few seconds). As for the second one, it sounds like it has not detected the presence of a tape - there's a switch in the cassette compartment which may be dirty and not operating. If the power supply was just dead before you repaired it, then it shouldn't have damaged anything. You can always unplug a board and swap it with the same one in the other machine, then see if the same fault has moved along with the board. If it does, then you know that board is faulty, otherwise it could be another board or something else like a motor, switch or sensor. The C7 was a very complex machine. I believe it had 3 microprocessors in total. Tracing logic faults is rather difficult.