Repair or adjustment of a Philips Brilliance 17A

[Peter Easthope]

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.

 

[Jon Elson]

Peter Easthope wrote:

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.
This may be a bad video cable. It could be reflections on the cable

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

 

[Peter Easthope]

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

This may be a bad video cable.  It could be reflections on the cable
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.

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

 

[Jeff Urban]

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

 

[Peter Easthope]

Thanks for the replies. Again a fresh thread because the original
is closed to further reply.

From: Jon Elson <jmel...@wustl.edu>
Date: Mon, 19 Dec 2011 14:37:22 -0600

This may be a bad video cable. It could be reflections on the cable
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.

To test, I replaced the beige colored cable about 1.5 m long and
apparently original, with a black colored cable about 2 m long and
skinnier. No significant difference in the display. For sake of
interest, the black cable was still folded and fastened with a twist
tie and inside the thin polyethylene sleeve from shipping. In
hindsight, not an arrangement to ignore. After a couple of hours
this way, the cable was quite warm to the touch. Luckily I was
paying attention and changed back to the heavy beige cable.
I wouldn't have expected a video cable to generate that much heat.
The current is too large or the black cable has wire cross-sections
pared a minimum, or both.

From: Jeff Urban <jurb6...@gmail.com>
Date: Wed, 21 Dec 2011 18:54:37 -0800 (PST)

... 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. ...
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.

So the practical conclusion is to replace this old monitor with a
flat
screen purchased for less than $100 from a local broker.

Thanks, ... Peter E.