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TonyDuell · 28th Aug 2017, 7:06 am

The KY80 is the only 2V Mullard valve that I have seen 'in the flesh', but there was a whole range of octal-based 2V valves used in old portable radios with a single lead-acid cell for LT.

If you have a bench supply, you could compare the KY80 filament glow when powered from that, set to 2V, (obviously with the valve out of the set, no EHT around) as against the glow when the valve is in the line output stage. It would give you an idea of whether the KY80 was getting anything like the right filament voltage.

28th Aug 2017, 7:06 am	#95
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Pilot PT650 "Spacemaker" Television The KY80 is the only 2V Mullard valve that I have seen 'in the flesh', but there was a whole range of octal-based 2V valves used in old portable radios with a single lead-acid cell for LT. If you have a bench supply, you could compare the KY80 filament glow when powered from that, set to 2V, (obviously with the valve out of the set, no EHT around) as against the glow when the valve is in the line output stage. It would give you an idea of whether the KY80 was getting anything like the right filament voltage.