How to narrow picture

[JohnCT]

Originally Posted by apple2dude

The only problem is that the overscan is great enough that it cuts off maybe 1/8 the picture on each side,

In the old days, TVs were always overscanned, particularly the vacuum tube models as it absorbed some aging of the sweep tubes. There weren't an awful lot of graphics on screen when these TVs were new as they were optical in nature. Today, inserting graphics is child's play, and because there is no scanning at all in flat panel displays, they can shove the graphics right to the very edge of the frame.

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