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FERNSEH · 8th Nov 2018, 10:30 pm

Andy has kindly constructed and supplied me another 4TP substitute module which again employs the ECL80 triode-pentode.

The original Cossor 4TP can now be considered impossible to find.

The attachments show the results. The Cossor 3244 CRT in my set is very poor condition and the workshop lights must be switched off to view any images on the screen.
The oscilloscope trace was taken from the anode of the triode section of the ECL80. It is quite safe to connect the oscilloscope X10 probe to this point but in order to take any scope traces from the anode of the pentode section a X100 probe must be employed to do this. Very high voltages exist on the anode of the pentode section.

Adjustment of height and width is achieved by selecting various values of anode load resistors for the pentode section of the 4TP frame oscillator and the MS-PEN line oscillator valves.

DFWB.

8th Nov 2018, 10:30 pm	#10
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Cossor 54 1938. Andy has kindly constructed and supplied me another 4TP substitute module which again employs the ECL80 triode-pentode. The original Cossor 4TP can now be considered impossible to find. The attachments show the results. The Cossor 3244 CRT in my set is very poor condition and the workshop lights must be switched off to view any images on the screen. The oscilloscope trace was taken from the anode of the triode section of the ECL80. It is quite safe to connect the oscilloscope X10 probe to this point but in order to take any scope traces from the anode of the pentode section a X100 probe must be employed to do this. Very high voltages exist on the anode of the pentode section. Adjustment of height and width is achieved by selecting various values of anode load resistors for the pentode section of the 4TP frame oscillator and the MS-PEN line oscillator valves. DFWB. Attached Thumbnails Last edited by Station X; 9th Nov 2018 at 10:50 am. Reason: Threads merged.