Repair or adjustment of a Philips Brilliance 17A

Mon Dec 19, 2011 7:29 pm   

Folk,

A photo of a small portion of the screen of a Philips Brilliance 17A
CRT computer monitor is here. http://members.shaw.ca/peasthope/PhilipsVideo.jpg

Notice the green ghost to the right of any dark area. Also, the
generally poor focus.
I've tried each of the two focus adjustments and found little
improvement.

Can anyone explain the greenness?

Is adjustment or repair of this old monitor advisable? Scrap it?

Thanks, ... Peter E.

Mon Dec 19, 2011 9:37 pm   

Peter Easthope wrote:


bouncing back and creating the ghost. It could also be a failed
termination resistor in the monitor, or a bad contact or broken solder
joint at the video connector.

Jon

Tue Dec 20, 2011 3:07 am   

On Dec 19, 12:37 pm, Jon Elson <jmel...@wustl.edu> wrote:

Thanks Jon, after Xmas I'll swap the video cable for one from a
working
system and report, ... Peter E.

Thu Dec 22, 2011 4:54 am   

Yes it could be the cable, but I think it would be a pretty rare
failure mode, maybe even a freak. I looked twice to make sure - this
IS a CRT monitor. In that case if the chassis has a floating filament
supply this could be an HK short in the green gun.

The trailing positive that makes the white after black green also
makes the black after white on some of the text magenta, which is
minus green. The frequency response of the green is limited, too much
capacitance. A standing wave anywhere in the green path could also be
at fault as someone already pointed out, but lots of CRTs short out
this way.

If so, if I have a print of the vid finals, the CRT soicket board, I
can maybe figure out how to EQ the vid output. I have done this more
that once. However I did that on NTSC units and I didn't worry about
FCC part 15 or anything. Those things only have about five Mhz video
bandwidth, this might be different.

There is a way to do this on almost any CRT based monitor, but the
question is whether it is worth it or not. The focus isn't really all
that bad but it ain't that good either. You have to differentiate that
from the smear in the green though, if the green was sharper it would
look sharper overall.

Without the print of the CRT socket board, ar at least a sheet on the
IC(s) on it, it's about impossible to do anything. In fact that's true
even if it's not an HK short.

J