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Old 20th Feb 2021, 8:27 pm   #338
FERNSEH
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Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
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Default Re: Baird T5 restoration project.

Hi Andy,
I've checked the DC resistances of the line scanning coils in the T5 and T23, both read 29ohms.
There is a 50mfd DC blocking capacitor in series with the scanning coils. It is safe to suggest the waveform at the grid of the 41MP triode is negative going as one would expect in an oscillator, the presence of the series capacitor will supply the coils with a sawtooth waveform symmetrical about zero.
All the Cossor 41MP triodes I've come across in Baird TV receivers are triode connected tetrodes or pentodes. Very early 41MP valves were true triodes.
High peak voltages are present at the anode of the line output valve, hence the ceramic valveholder.
Some info about the Cossor 41MP: https://www.radiomuseum.org/tubes/tube_41mp.html

DFWB.
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