UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

FERNSEH · 25th Apr 2018, 11:06 pm

The Ultra V17-53 is on the work bench. The oscilloscope is connected to the secondary of the frame output transformer. At the correct height control setting the flyback pulse is about 60 volts negative. The leading edge has a rapid rise time and the trailing edge has a slope which takes about 300microseconds to come down to zero.
I'm not sure if -60 volts is sufficient for the gate function. We have to consider that a delay circuit has to be introduced so that the black level sampling takes place outside the frame sync eight broad pulses sync sequence.

The positive going flyback pulse at the anode of the frame output valve is something like 500 volts.

DFWB.

25th Apr 2018, 11:06 pm	#20
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Frame gated AGC modifications The Ultra V17-53 is on the work bench. The oscilloscope is connected to the secondary of the frame output transformer. At the correct height control setting the flyback pulse is about 60 volts negative. The leading edge has a rapid rise time and the trailing edge has a slope which takes about 300microseconds to come down to zero. I'm not sure if -60 volts is sufficient for the gate function. We have to consider that a delay circuit has to be introduced so that the black level sampling takes place outside the frame sync eight broad pulses sync sequence. The positive going flyback pulse at the anode of the frame output valve is something like 500 volts. DFWB.