Re: 475 With a bowed display. . . .Ideas?


On Sat, Aug 8, 2020 at 04:40 PM, Michael W. Lynch wrote:

If it was just one minor division of deviation, I could live with this, but
the outermost vertical markers are about 6 minor divisions "leaned in" at the
top of the marker. It is almost like looking through a "fisheye" lens.

I'd think that's way out of range for the electrical Geometry adjustments that you mentioned earlier, so probably something is wrong of the sort that Chuck describes. It may be worthwhile to quickly check if the Geometry adjustment pot's range reaches the intended 0 to +110V. It's GND-related, so not dangerous to measure, unlike grid- and focus- voltage levels.

Re. the "fisheye" appearance: Is the distortion mostly (radially) symmetrical? In that case, I wouldn't think it could be just a moved magnet.

Trying another CRT seems to make sense. Not too much hassle with a 465/475. Just the usual care with the lingering anode voltage.

BTW, re. the first post, Michael wrote:

"Problem was C1442 was bad. High resistance and almost no capacitance, loading the +15V supply."

The high resistance and low capacitance resulted in your meter showing that the average or RMS voltage was too low so good regulation wasn't possible.
C1442 wasn't loading the +15V supply ("high resistance") but loading the 15V supply wasn't possible, since the regulation circuit received practically unbuffered rectified AC. It's probably what you meant.


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