1959 21TX250A Philips TV. - UK Vintage Radio Repair and Restoration Discussion Forum

GrupoPatel · 16th Nov 2018, 10:18 pm

Hello and thanks for reading.
I just got this TV and I have repaired the audio reception, but I am blocked with the image. The screen is black, All lamps turn on, including the picture tube, but only a very slight white flash is seen when I rotate the brightness pot from V g1 50v to 140 v.
I have measured the voltages on pl36, PY81 and ECC82 (B17) and they are correct.
My first suspicion is focused on the DY87 ... no lighting is appreciated. However, its filament is ok tested externally at 1.4 v (@ 0.6 amp), but the brightness of the filament is very weak, and it is not appreciated when mounted. Before looking for an insulation transformer (the chassis is directly connected to 220v of the network) and continue investigating with the oscilloscope, the question arises: the DY87 should be illuminated ?, should its filament be seen? .. or on the other hand should be completely without any brightness to denote that its operation is correct ?.
Here is the schematics : https://frank.pocnet.net/instruments...A/21TX250A.pdf

16th Nov 2018, 10:18 pm	#1
GrupoPatel Retired Dormant Member Join Date: Nov 2018 Location: Seville, Spain Posts: 1	1959 21TX250A Philips TV. Hello and thanks for reading. I just got this TV and I have repaired the audio reception, but I am blocked with the image. The screen is black, All lamps turn on, including the picture tube, but only a very slight white flash is seen when I rotate the brightness pot from V g1 50v to 140 v. I have measured the voltages on pl36, PY81 and ECC82 (B17) and they are correct. My first suspicion is focused on the DY87 ... no lighting is appreciated. However, its filament is ok tested externally at 1.4 v (@ 0.6 amp), but the brightness of the filament is very weak, and it is not appreciated when mounted. Before looking for an insulation transformer (the chassis is directly connected to 220v of the network) and continue investigating with the oscilloscope, the question arises: the DY87 should be illuminated ?, should its filament be seen? .. or on the other hand should be completely without any brightness to denote that its operation is correct ?. Here is the schematics : https://frank.pocnet.net/instruments...A/21TX250A.pdf