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Old 3rd Sep 2019, 2:25 pm   #205
FERNSEH's Avatar
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,440
Default Re: Baird T5 restoration project.

Argus25 wrote: "The purpose of the resistor in series with the diode is to isolate the diode's capacitance from the video signal. If it is too large the restorer's effectiveness is diminished. The typical value RCA chose was around 10k to 47k as I recall, it needs to be at least as big as the anode resistor in the plate of the video output valve and not much bigger in value. Maybe, looking at the photo you posted, its a 22k not a 220k ? Check it on the meter, if it reads 200k, maybe its a gone very high 22k ? "
The resistor in series with the WX6 is indeed 22Kohms and is well within tolerance for such an old component.
Yesterday evening the EHT cable to the tube anode was disconnected and voltages and waveforms on the CRT grid checked to see if there would be any changes. Results were just the same as with EHT. So it's has to be leakage between the grid and cathode that's causing the brightness control and DC restorer not to work correctly.
The CRT will be taken out later today and that wire link between the cathode and heater will be removed. The tube cathode connection will be free for the brightness control as it is in the model T20.

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