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原帖由: jim jimx ,

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©2000 Thomas H. Lee, rev. May 31, 2007; All rights reserved

5.2 Height and Width

If you want the screen to provide true WYSIWYG so that 1” on the display corresponds to 1” in real life, then its dimensions must be precise, or 4.75” x 7.11”, to be more exact (that’s 342x512 pixels at 72 pixels per inch). Unlike the other four adjustments, adjusting the width requires a hexagonal tool made of a NONCONDUCTIVE, NONMAGNETIC material. You can get these tools at places like Radio Shack, where a suitable one is sold as a tuner alignment tool. You can make a serviceable one out of a whittled down wooden chopstick or some similar material. If you use a cheap chopstick, you don’t have to do much work at all. Cheap chopstick wood is soft, so tapering it enough to allow gently jam- ming it into the core of the control is usually good enough. It will conform to the shape of the core well enough to do the job.

The reason for the nonconductivity requirement is that the control is actually a ferrite core inside an inductor carrying large alternating currents. The AC field would induce large currents in a conductive tool, and make it get incredibly hot very quickly, to say nothing of invalidating the adjustment. At the same time, the increased strain that this places on the circuits could cause damage. So, wood or plastic it should be. Once you have the tools, you can save time by tweaking the height to 4.75” and then adjusting the width until diag- onal rows of raster dots are at right angles to each other. A piece of paper or a floppy disk or any other handy object with right angles will do as a good template for this purpose.

If you don’t care about WYSIWYG, then just making the dots at right angles is good enough to preserve proper aspect ratio.

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