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In Reply to: RE: Sony Cassette Deck Low Playback Volume problem posted by rotovator on June 01, 2007 at 18:27:29
The plot thickens. I followed your suggestions using a cassette that I had recorded. I tried to record some FM interstation noise in mono, and found that the erase head does not seem be working correctly, since the original program is still present, just with some noise taped over it.
Obiviously with the original program still on the tape, I couldn't make any comparisons. I'm not even sure of the significance of this except it might be another clue. Any idea how this fits in?
Thanks,
Mike
Follow Ups:
When the deck doesn't erase the tape you have to check if it stills records well or distorted. In the latter, the bias circuit is not working, and I think that in a three head deck, bias circuit and playback circuits are completely isolated.
So, you are having two different problems.
Peace
I found the pots for the playback volume and got it up to an acceptable level. However, in addition to the erase head, record doesn't work either. I either get a hum in one channel or a rhythmic clicking in both, depending on what adjustments I try. i found a the labeled bias oscillator on the board and it has a provision for adjusting both channels. Should a take a shot and risk making things worse?
Mike
I don't think that adjusting bias level could do any good if recording is so bad. Anyway, it's a good idea to turn pots to prevent bad contacts from oxide in the pot itself. And the worst you can do is to dis-adjust the bias level, not catastrophic. You can measure with a resistence-meter before to be able to leave the pot as you found it.
The bias circuit is the most prone to fail in decks. Specially the capacitors in the oscillator. With an oscilloscope or a AC-voltmeter you could check the circuit function. It has a small transformer (can be cylindrical) that raises the output voltage to the erase head and recording circuit up to more than 80-100 volts. Check for that AC-voltage when recording, for example, in the pins of the recording or erasing head.
I checked it with my DMM on AC. Reading was 0 volts. Looks grim.
Regards,
Mike
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