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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 8th Aug 2020, 12:05 pm   #1
regentone001
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Default Regentone Ten-17

Hi
this set has been working well since I restored it, basically I rebuilt the circuit board, but it has now developed an irritating fault.
After it has been on for a while it develops bands of light and dark stripes across the picture, most of the time they are barely visible, if not invisible at other times they are quite obvious. but they are not strong enough to be visible on a photo unfortunately.
The stripes are about 1/4 inch wide and they are all the way down the screen.
I have tried changing the PCF80 video output valve and the 3 EF80s in the IF still no difference.
I don't know whether it is related but the brightness control is almost at the lowest end of its track and the picture can be over bright, fly back lines are clearly visible too at times. Any ideas will be most welcome

Thanks Steve
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Old 8th Aug 2020, 10:02 pm   #2
slidertogrid
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Default Re: Regentone Ten-17

Unfortunately it may be a heater to cathode leak in the tube. There are of course other things that could cause this but HK leakage will affect the brightness range and cause the effect you describe.
If you have a CRT heater transformer you could try running the heaters from that and see if it makes any difference...
Hopefully I am wrong and its a fault in the video output stage!
Rich.
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Old 8th Aug 2020, 10:17 pm   #3
Heatercathodeshort
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Default Re: Regentone Ten-17

Worth checking the value of R31 the anode load to the video amplifier. It should be 10K. [R & TV servicing]connected between HT line and Pin 6 of PCF80 video output. J.
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Old 11th Aug 2020, 12:18 pm   #4
regentone001
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Default Re: Regentone Ten-17

It appears that the stripes of light and dark are caused by atmospheric conditions. They have faded away the worst time was on Sunday it was almost unwatchable now it is back to normal. I am waiting for a filament transformer to arrive and hopefully that will cure the over brightness
Thanks for the suggestions
Steve
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