Quote:
Originally Posted by JohnCT
But on to your problem. Zeno is right in that playing around with the sweep can cause problems, but there is an easy way that can get your sweep down without causing trouble. The good news is that it will reduce your sweep, the potentially bad news is that the HV goes up at the same time and may stress components, but a *little* increase won't hurt.
Locate the retrace capacitor across the horiz output transistor (goes from collector to ground). Remove it and replace it with a *slightly* lower value making sure to keep the same voltage *and* type of capacitor in your sub. You will have to experiment but a small change of value downward will have a fairly large effect on the width and of course, HV.
If your selected capacitor sub is too low, you can leave it in place and add a smaller value disc capacitor across it to "trim" it.
John
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Solid state sets were sometimes designed with longer retrace time than standard to reduce the pulse height on the output transistor. In other words, your problem may be more than just too wide sweep, but may also be too long a retrace. Using a smaller cap reduces the retrace time, but for this to work it has to also compensate for any remaining overscan, so a double whammy. So, take baby steps so you just barely get enough change.
Broadcasters used to rag on TV makers about how much image was wasted by overscan; camera viewfinders often had a safe title graticule attached, and safe title area specs were published by SMPTE. When TV sets went backwards in tube shape (from rectangular tubes for monochrome to round tubes for color), color studios might even use a "double D" safe area graticule.
https://www.nab.org/xert/scitech/pdfs/tv031510.pdf
02-03-2021, 10:10 PM
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