Thanks, lads. Here's a up-date.
I found a ceramic capacitor marked 471K and fitted that as C13. This made no odds.
I managed to find a polystyrene one marked 121J which I tried as both C11 and C12 (trying not to think about the voltage rating) but this made no difference either.
There's no sign of earth faults on L3.
I don't have a signal generator and can't see there being anything amiss with the wave change switch or tuning capacitor given that it works fine as a crystal set.
I tried Tony's test on pin 9 and the AVO needle did move backwards SLIGHTLY on the 2.5VDC range. It wasn't enough to measure so I put the digital one on and that read 0.3V positive, as did the AVO when I tried that again. This seems like it either changed as the set fully warmed up or the polystyrene cap had had enough.
I'm starting to suspect the valve. When I first looked at this set and found the o/c dropper I got in touch with a professional restorer with a view of purchasing a replacement. I also mentioned that this valve looked very silvered within but he replied that this was nothing to worry about and it's a 'milky' appearance that is a cause for concern. I've since seen quite a few valves but have never seen anything else approaching this though. Here are some photos so see what you think. Needless to say I haven't got a spare.
I certainly wouldn't be surprised if it is faulty as the resistors I replaced were so far out it could well have been working well outside its rating before the dropper went.
Thanks for the help, it's nice to at least have the area of difficulty narrowed down.
- Joe
EDIT: I should have said this before but I'm working with an ERT Service Chart though also have access to the R&TS version.
I found a ceramic capacitor marked 471K and fitted that as C13. This made no odds.
I managed to find a polystyrene one marked 121J which I tried as both C11 and C12 (trying not to think about the voltage rating) but this made no difference either.
There's no sign of earth faults on L3.
I don't have a signal generator and can't see there being anything amiss with the wave change switch or tuning capacitor given that it works fine as a crystal set.
I tried Tony's test on pin 9 and the AVO needle did move backwards SLIGHTLY on the 2.5VDC range. It wasn't enough to measure so I put the digital one on and that read 0.3V positive, as did the AVO when I tried that again. This seems like it either changed as the set fully warmed up or the polystyrene cap had had enough.
I'm starting to suspect the valve. When I first looked at this set and found the o/c dropper I got in touch with a professional restorer with a view of purchasing a replacement. I also mentioned that this valve looked very silvered within but he replied that this was nothing to worry about and it's a 'milky' appearance that is a cause for concern. I've since seen quite a few valves but have never seen anything else approaching this though. Here are some photos so see what you think. Needless to say I haven't got a spare.
I certainly wouldn't be surprised if it is faulty as the resistors I replaced were so far out it could well have been working well outside its rating before the dropper went.
Thanks for the help, it's nice to at least have the area of difficulty narrowed down.
- Joe
EDIT: I should have said this before but I'm working with an ERT Service Chart though also have access to the R&TS version.
