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FERNSEH · 17th Jul 2017, 10:46 pm

The HT supply to the line timebase should be >240volts. You can measure this at one end of the screen feed resistor of the EL38. The line timebase operates as a type of Miller transiton oscillator. Forward part of the scan comes from the ramp waveform developed in the primary of the line output transformer and the flyback is a function of the capacitor connected between the screen and suppressor grids of the EL38. The spark present at the anode will be tiny and at the anode of the EY51 only 4 to 5 mm. EHT is between 6 to 7KV.
It has to be an EL38 in this type of chassis. Beam tetrodes like the Mazda 6P28 won't work properly.
The metal HT rectifier is not the usual 14A86 type. It's special one for this set.

DFWB.

17th Jul 2017, 10:46 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Decca 101 restoration The HT supply to the line timebase should be >240volts. You can measure this at one end of the screen feed resistor of the EL38. The line timebase operates as a type of Miller transiton oscillator. Forward part of the scan comes from the ramp waveform developed in the primary of the line output transformer and the flyback is a function of the capacitor connected between the screen and suppressor grids of the EL38. The spark present at the anode will be tiny and at the anode of the EY51 only 4 to 5 mm. EHT is between 6 to 7KV. It has to be an EL38 in this type of chassis. Beam tetrodes like the Mazda 6P28 won't work properly. The metal HT rectifier is not the usual 14A86 type. It's special one for this set. DFWB.