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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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uPC1161C - anyone familiar with or similar VCO stereo radio ICs
I have in circuit details and pin 9 is the test point for
19KHz mionitoring but I only have representative DC voltages and pin-out. No stereo in a radio and only about 5mV pk-pk square wave signal on this pin. As you should be able to connect a f meter here , pin 9, to adjust to 19KHz would I be right in thinking there should be more than 5mV |
#2
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Finally dug out the service manual.
Pin 9 is the stereo lamp drive line. The manual shows no 19kHz monitor pin on the mpx chip, and vr302 is adjusted merely to light the stereo lamp when fed a stereo signal from a generator, then vr303 for maximum separation. The most likely reason for not being able to get stereo is misadjustment of L703 & L704 discriminator transformers on the IF board. Incidentally, on your previous question, the dolby fm board was optional, so most 730's don't have it & thus the dolby fm button simply cuts off the signal. -- Stephen Sank, Owner & Ribbon Mic Restorer Talking Dog Transducer Company http://stephensank.com 5517 Carmelita Drive N.E. Albuquerque, New Mexico [87111] 505-332-0336 Auth. Nakamichi & McIntosh servicer Payments preferred through Paypal.com "N Cook" wrote in message ... I have in circuit details and pin 9 is the test point for 19KHz mionitoring but I only have representative DC voltages and pin-out. No stereo in a radio and only about 5mV pk-pk square wave signal on this pin. As you should be able to connect a f meter here , pin 9, to adjust to 19KHz would I be right in thinking there should be more than 5mV |
#3
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I ended up replacing 8 bulbs as I suspected lack of radio may be due to
not knowing which functions on or off.on the Nakamichi 730. I will burrow around for more data on the uPC1161 and explore the radio a bit more. Failing that I've a couple of salvaged ones I could try in place. The odd thing there is a setting of the pots where I can get the stereo light to work but even putting a crystal earpiece to pin 6 and another to pin 7 definitely not stereo. Otherwise reception is perfectly good "Stephen Sank" wrote in message ... Finally dug out the service manual. Pin 9 is the stereo lamp drive line. The manual shows no 19kHz monitor pin on the mpx chip, and vr302 is adjusted merely to light the stereo lamp when fed a stereo signal from a generator, then vr303 for maximum separation. The most likely reason for not being able to get stereo is misadjustment of L703 & L704 discriminator transformers on the IF board. Incidentally, on your previous question, the dolby fm board was optional, so most 730's don't have it & thus the dolby fm button simply cuts off the signal. -- Stephen Sank, Owner & Ribbon Mic Restorer Talking Dog Transducer Company http://stephensank.com 5517 Carmelita Drive N.E. Albuquerque, New Mexico [87111] 505-332-0336 Auth. Nakamichi & McIntosh servicer Payments preferred through Paypal.com "N Cook" wrote in message ... I have in circuit details and pin 9 is the test point for 19KHz mionitoring but I only have representative DC voltages and pin-out. No stereo in a radio and only about 5mV pk-pk square wave signal on this pin. As you should be able to connect a f meter here , pin 9, to adjust to 19KHz would I be right in thinking there should be more than 5mV |
#4
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Found a Sony manual with uPC1161 details and it mentions
pin 9 as being both stereo indicator driver and VCO oscillator test point but this time monitoring 76KHz instead of 19. Can't get hold of the owner so I will put on hold for afew days. |
#5
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I would suggest replacing the few small electrolytics around the mpx chip before assuming the
chip is bad. -- Stephen Sank, Owner & Ribbon Mic Restorer Talking Dog Transducer Company http://stephensank.com 5517 Carmelita Drive N.E. Albuquerque, New Mexico [87111] 505-332-0336 Auth. Nakamichi & McIntosh servicer Payments preferred through Paypal.com "N Cook" wrote in message ... Found a Sony manual with uPC1161 details and it mentions pin 9 as being both stereo indicator driver and VCO oscillator test point but this time monitoring 76KHz instead of 19. Can't get hold of the owner so I will put on hold for afew days. |
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