I have an old Sharp HI-FI VCR in the shop that belongs to a good friend of mine. This was a high-end unit and it is still in very good shape, other than it won't tune in any channels. This machine was from 1985 and it has the electrically powered drawer on the front panel that opens up to reveal the remote control and function buttons. If it belonged to anyone else, I'd say to forget it but I would like to solve the problem in this case.
The VCR tuning circuitry is not functioning. Just snow on the screen. I replaced the tuner without improvement. I believe the problem is in the frequency synthesizer circuit. Some of the voltages around the PLL IC 1401 are wrong. On the tuner, the VT pin is zero volts and the B2 terminal should have 11V but it is zero. I injected my own voltages to these pins and was able to tune in a channel. I have replaced the band switching IC 1503 (IX0260CEZZ or LA7910) and tested transistor voltages and the 4.5Mhz crystal is at correct frequency.
I am hoping that someone has one of these units sitting on a shelf waiting to be sold at a reasonable price for parts. I'd especially like to get the synthesizer, tuner, and timer boards.
Thanks for any help. --
Gary McCartney
McCartney Electronics Guelph Ontario Canada Est. 1984 email: gary (at) number63.ca
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