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PJL · 12th Apr 2019, 7:42 pm

Agreed, the HT is around 200V so R25 (220K) has about 50V across it which gives us about 220uA anode current and it should be about 10x that according to the datasheet. The low emission may also affect the diode (V4c) used as the detector.

Can you measure the AC voltage on V4 heater, between pins 4 & 5.

12th Apr 2019, 7:42 pm	#86
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ferguson 382U Firefly not playing ball Agreed, the HT is around 200V so R25 (220K) has about 50V across it which gives us about 220uA anode current and it should be about 10x that according to the datasheet. The low emission may also affect the diode (V4c) used as the detector. Can you measure the AC voltage on V4 heater, between pins 4 & 5.