09-09-2018, 07:25 PM
Update...
The TV sound receiver is now working, I had to replace the audio amplifier interstage coupling capacitor and now I can hear a test tone when I feed a modulated rf signal into the aerial socket. local oscillaror frequency seemed about right too although connecting the probe probably shifted it a bit anyway.I can also see bands on the video so I guess the RF sections are not far off. When I have Frank's convertor / generator working I'll know for sure.
Another fault on the audion was a dry cathode decoupling capacitor, when the amp started to work it was also motoboating in a way which affected the picture too.
I also had an accident being a bit rough and careless de-soldering a component off one of a valve bases and broke in half a pin socket, fortunateley I have a brand new socket which I used to donate a single pin to repair the socket in-situ.
Lookig inside the cabinet I discovered a round loudspeaker in the place where an eliptical one should be, I expect the old repair man did that back in its day, cant imagine that was a factory kludge.
I'm struggling with the frame timebase though. I havn't yet got a full height raster and the hold is at one end of the controll. I was led up a blind alley when my meter went wonky and gave some misleading resistor readings. I was supried to see a 2M2 resistor reading 800K, it was a false reading, doh. I switched my multimere off and on again and it gve the correct reading - never had that before.
I dont really know the details about how the frame timbase works so diagnosis is difficult but I'll carry on checking values and substituting with known good parts. I've swapped a couple of ECL80s over and it helped a bit but I may try ones out of my other Tv to be sure.
Kind regards, David.
The TV sound receiver is now working, I had to replace the audio amplifier interstage coupling capacitor and now I can hear a test tone when I feed a modulated rf signal into the aerial socket. local oscillaror frequency seemed about right too although connecting the probe probably shifted it a bit anyway.I can also see bands on the video so I guess the RF sections are not far off. When I have Frank's convertor / generator working I'll know for sure.
Another fault on the audion was a dry cathode decoupling capacitor, when the amp started to work it was also motoboating in a way which affected the picture too.
I also had an accident being a bit rough and careless de-soldering a component off one of a valve bases and broke in half a pin socket, fortunateley I have a brand new socket which I used to donate a single pin to repair the socket in-situ.
Lookig inside the cabinet I discovered a round loudspeaker in the place where an eliptical one should be, I expect the old repair man did that back in its day, cant imagine that was a factory kludge.
I'm struggling with the frame timebase though. I havn't yet got a full height raster and the hold is at one end of the controll. I was led up a blind alley when my meter went wonky and gave some misleading resistor readings. I was supried to see a 2M2 resistor reading 800K, it was a false reading, doh. I switched my multimere off and on again and it gve the correct reading - never had that before.
I dont really know the details about how the frame timbase works so diagnosis is difficult but I'll carry on checking values and substituting with known good parts. I've swapped a couple of ECL80s over and it helped a bit but I may try ones out of my other Tv to be sure.
Kind regards, David.
