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[email protected] ZZactly@aol.com is offline
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Default KP48S65 Horiz sync problem

We have a word for problems like this one, but I'll refrain from using
it in public.

On a high brigthness signal it jitters about an inch back and forth. On
a test pattern there is a slight wave in it, but it is hard to see on
normal video. That is so slight that it almost could be left alone, but
it's surely related to the jitter.

I changed C 338 which is the low freq portion of the AFC filter
network. Also changed IC 301 to no avail. I also bypassed C333 which
didn't do anything.

I see pin 38 is also fed by Q 314. It seems to get an inverted ABL
signal there. To eliminate that as a suspect I disabled it temporarily
by shorting Q 314 E to B. Still doing it.

Looking further, with the spec sheet for the CXA2025AS I find pin 37 is
called L2LFIN. The spec sheet says to bypass it and that you can use DC
to shift the H sync phase. I have also bypassed that with a .01, which
is plenty since it is fed through a 470K resistor (R 375).

There is also something not quite right abut the picture. It looks like
the video is slightly clipped on the whites. Naturally I checked the
signal at the HSIN pin 44. From the sync tips to the top of a staircase
waveform it is exactly 2.0 V P-P, as called for in the print.

Anything you might have on this would be greatly appreciated.

JURB