UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Philips 663A combined radio/television 1948

matspar · 27th Apr 2021, 11:44 pm

Hi everyone,

Many thanks for your suggestions! here is the relevent bit of circuit.

There are a pair of ECH35's as frequency changers, one sound one vision. My first thought was something not right early on in the V1 area as there is no sound or vision, however I can't find anything amiss here. I have replaced the 0.004uf decouplers which were originals. All windings intact. Slowly adjusting S2 will produce some very slight noise with a signal applied.

Touching the anodes and grids of V1 & V2 will cause disturbance and HT is well up to spec. Could both ECH35's be low I wonder. My valve tester has thrown its toys out of the pram so I'm currently unable to test. The EF50 (V1) is a known good one.
I haven't explored the contrast circuit fully apart from the obvious. Pot intact but it doesn't have much of an effect on the raster when adjusting. The sensitivity link is in place.
Bit of a mystery this one but a fantastic set to restore. Any more thoughts gents?

27th Apr 2021, 11:44 pm	#12
matspar Pentode Join Date: Aug 2009 Location: Portsmouth, Hampshire, UK. Posts: 230	Re: Philips 663A combined radio/television 1948 Hi everyone, Many thanks for your suggestions! here is the relevent bit of circuit. There are a pair of ECH35's as frequency changers, one sound one vision. My first thought was something not right early on in the V1 area as there is no sound or vision, however I can't find anything amiss here. I have replaced the 0.004uf decouplers which were originals. All windings intact. Slowly adjusting S2 will produce some very slight noise with a signal applied. Touching the anodes and grids of V1 & V2 will cause disturbance and HT is well up to spec. Could both ECH35's be low I wonder. My valve tester has thrown its toys out of the pram so I'm currently unable to test. The EF50 (V1) is a known good one. I haven't explored the contrast circuit fully apart from the obvious. Pot intact but it doesn't have much of an effect on the raster when adjusting. The sensitivity link is in place. Bit of a mystery this one but a fantastic set to restore. Any more thoughts gents? Attached Thumbnails __________________ Matt https://www.youtube.com/channel/UCGj...D79hH9a_kMowcA Last edited by matspar; 27th Apr 2021 at 11:55 pm.