UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

FERNSEH · 15th Mar 2017, 2:42 am

I'm very impressed with the work that is being carried out to save what is a very rare set. I doubt if there is another similar set still in existence. We are all looking forward to seeing the end result.
The 21" Pilot "Spacemaker" with FM radio was designated as the model PT651.
The addition of FM radio was done in a very thorough manner. Although the tuner unit is common to TV and FM, when radio is selected the output from the tuner is the standard 10.7Mhz IF. The FM signals are processed by a separate two stage IF amplifier and a double-diode ratio detector. The resultant audio is passed to the reflex TV sound IF amplifier. The clever part of the circuit is the method of supplying power to the FM amplifier unit. On FM the line timebase is switched off and the HT line then supplies the 0.1amp series heater chain of the FM valves. The valves are two Mazda 10F18 pentodes and a Mazda 10D2 double diode.
Later TVs with FM employed a slightly different radio IF amplifier unit. The 10D2 was replaced by a 10LD12 triple-diode-triode. Check out my topic about the Ultra V1781. This set has FM radio.

DFWB.

15th Mar 2017, 2:42 am	#26
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Pilot PT650 "Spacemaker" Television I'm very impressed with the work that is being carried out to save what is a very rare set. I doubt if there is another similar set still in existence. We are all looking forward to seeing the end result. The 21" Pilot "Spacemaker" with FM radio was designated as the model PT651. The addition of FM radio was done in a very thorough manner. Although the tuner unit is common to TV and FM, when radio is selected the output from the tuner is the standard 10.7Mhz IF. The FM signals are processed by a separate two stage IF amplifier and a double-diode ratio detector. The resultant audio is passed to the reflex TV sound IF amplifier. The clever part of the circuit is the method of supplying power to the FM amplifier unit. On FM the line timebase is switched off and the HT line then supplies the 0.1amp series heater chain of the FM valves. The valves are two Mazda 10F18 pentodes and a Mazda 10D2 double diode. Later TVs with FM employed a slightly different radio IF amplifier unit. The 10D2 was replaced by a 10LD12 triple-diode-triode. Check out my topic about the Ultra V1781. This set has FM radio. DFWB. Last edited by FERNSEH; 15th Mar 2017 at 2:50 am.