uPC1161C - anyone familiar with or similar VCO stereo radio ICs

[N Cook]

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

 

[Stephen Sank]

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]

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

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

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

 

[N Cook]

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.

 

[Stephen Sank]

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