UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 1948/1949 Philips type 520A television and radio

FERNSEH · 31st Jul 2016, 11:13 am

Good morning Jac,
Just like the 563A there are some quite adventurous circuits in the 520A and 521A. The sound circuits in particular. Switched to radio operation the set performs just like a conventional receiver using 0.2amp heater chain valves, CCH35, EF39, EBC33 and CL33, Just to add to the confusion the radio HT rectifier is a 0.1amp heater type UY21. Radio IF is 470Khz.
On television all the 0.2amp radio valves remain in the circuit, the CCH35 performs as the sound frequency changer, The television sound IF is 9.8Mhz.
When switched to television an additional sound IF amplifier stage is introduced using an EF50.
Most of the television circuits resemble the 563A, however because no mains transformer is employed for the higher HT voltage required by the line timebase a voltage doubler circuit is used by employing a PZ30 double diode.
Thus the set cannot be used on DC mains.
Information for the Mullard version, the MT521 can be found in pages 592 to 601 of volume II Radio and Television Servicing by Molloy and Poole.

DFWB

31st Jul 2016, 11:13 am	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: 1948/1949 Philips type 520A television and radio Good morning Jac, Just like the 563A there are some quite adventurous circuits in the 520A and 521A. The sound circuits in particular. Switched to radio operation the set performs just like a conventional receiver using 0.2amp heater chain valves, CCH35, EF39, EBC33 and CL33, Just to add to the confusion the radio HT rectifier is a 0.1amp heater type UY21. Radio IF is 470Khz. On television all the 0.2amp radio valves remain in the circuit, the CCH35 performs as the sound frequency changer, The television sound IF is 9.8Mhz. When switched to television an additional sound IF amplifier stage is introduced using an EF50. Most of the television circuits resemble the 563A, however because no mains transformer is employed for the higher HT voltage required by the line timebase a voltage doubler circuit is used by employing a PZ30 double diode. Thus the set cannot be used on DC mains. Information for the Mullard version, the MT521 can be found in pages 592 to 601 of volume II Radio and Television Servicing by Molloy and Poole. DFWB Last edited by FERNSEH; 31st Jul 2016 at 11:39 am.