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Old 28th Aug 2017, 3:13 pm   #42
matspar
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Join Date: Aug 2009
Location: Portsmouth, Hampshire, UK.
Posts: 230
Default Re: And the next one! a GEC BT2147

Thanks Nick I've had a play with the values today and it seems quite happy with an 18R 5W resistor. HT just about right and no overheating. Andy - after a bit of head scratching I discovered that V14 N37 frame output valve has an internal short. I swapped it for V15 which also uses an N37 as the audio output, as I don't have a spare to hand. It doesn't seem to object so far but I will source a new pair. Still no luck with the frame collapse. been through every cap and resistor in the frame circuit and all were ok except R38 680k which had shot up to 1.7M. So I'm thinking valve trouble now. I did suspect the height slider but this seems to read fine when cold and voltages are quite normal when on. I don't appear to be getting the correct HT on V7 N77 or V8 B36 (now a 12SN7) The trader sheet says there should be 160v and 158v respectively but I'm getting around 80v at best. What am I missing here.
Thanks for the tuner info David makes very interesting reading - will be the next challenge no doubt if I get that far.

Thankyou all
Matt
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