What kind of CRT monitor problem is THIS?

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

To the right of dark objects on light background (eg. text,
scrollbars, etc.), there are several lines that tail it. Looks
something like:

||| || |

Those are vertical lines. Starts out thicker, then dissipates
(narrower and lighter) as it goes to the right until they dissappear.
Most noticable if the object is black on a white background.

I tried photographing it but my digicam just can't pick it up. I have
a gut feeling this is a common problem. I just don't know the name of
it. What causes it? And is there an easy fix?

The monitor in question is a Sony GDM-F520 ("Trinitron" type) paired
to a Matrox Parhelia. I tested with another GDM-F520 under the same
conditions and it does not exhibit the problem as the first monitor.
Problem starts showing up a few hours after the monitor is turned on
after several hours being off. I noticed turning the monitor off and
then back on can make the problem go away for a few minutes upon which
it returns. Degaussing has no effect.

Thanks.

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"Richard Lee" <r@r.com> wrote in message
news:m3cga0103q9ca6a5b5viva6t1oieq8fl14@4ax.com...
> To the right of dark objects on light background (eg. text,
> scrollbars, etc.), there are several lines that tail it. Looks
> something like:
>
> ||| || |
>
> Those are vertical lines. Starts out thicker, then dissipates
> (narrower and lighter) as it goes to the right until they dissappear.
> Most noticable if the object is black on a white background.

Sounds like ghosting (signal reflections), most likely due to
a mismatch somewhere in the video cable or at the input to
the monitor. You wouldn't happen to be using an extension
cable or switchbox, would you? Or have the input termination
of the monitor set to something other than 75 ohms?

There are a couple of other, more complicated (from the standpoint
of repair) possibilities, but let's try this one first.

Bob M.
..

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

>Sounds like ghosting (signal reflections), most likely due to
>a mismatch somewhere in the video cable or at the input to
>the monitor. You wouldn't happen to be using an extension
>cable or switchbox, would you? Or have the input termination
>of the monitor set to something other than 75 ohms?

The GDM-F520 doesn't allow you to change the termination resistance.
But yeah, I know what you are talking about. In another monitor I had
previously, there was a little switch at the back for that.

No extension nor swtichbox. Tried a thick (and I mean THICK) BNC
cable. Seemed to help a bit but did not totally eliminate the problem.
The other GDM-F520 that is beside it is good with or without a BNC
cable.

You still think it's a ghosting prob?

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"Richard Lee" <r@r.com> wrote in message
news:kauia0592tdu6882gemh5g7otrjuvg9c1a@4ax.com...
> >Sounds like ghosting (signal reflections), most likely due to
> >a mismatch somewhere in the video cable or at the input to
> >the monitor. You wouldn't happen to be using an extension
> >cable or switchbox, would you? Or have the input termination
> >of the monitor set to something other than 75 ohms?
>
> The GDM-F520 doesn't allow you to change the termination resistance.
> But yeah, I know what you are talking about. In another monitor I had
> previously, there was a little switch at the back for that.
>
> No extension nor swtichbox. Tried a thick (and I mean THICK) BNC
> cable. Seemed to help a bit but did not totally eliminate the problem.
> The other GDM-F520 that is beside it is good with or without a BNC
> cable.
>
> You still think it's a ghosting prob?

It does really sound like classical ghosting. Another possible cause is
termination problems in the
video card. What happens if you swap the monitors? Does the artifact follow
the monior, or stay with the
system?
It may be internal electronics if the artifact follows the monitor.

HTH

Not Gimpy Anymore

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

Ghosting is often caused by bad capacitors on the CRT neck board,
especially those near the video amp IC. You should check these
using an ESR meter to locate those with high internal resistance.
John

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

> It does really sound like classical ghosting. Another possible cause is
>termination problems in the
>video card. What happens if you swap the monitors? Does the artifact follow
>the monior, or stay with the
>system?
> It may be internal electronics if the artifact follows the monitor.

Appears to follow the monitor. Suppose monitor A was the one showing
the problem. If I switch the cables around such that monitor A now
gets its signal from graphics card port B, and monitor B gets its
signal from graphics port A, monitor A still shows the problem.

What internat electronics? Could being knocked aound during shipping
be a possible cause? Is this sort of thing easy or difficult to fix?

Some misc notes which you may have already know/figured out:
- The Matrox video card allows for dual head operation. There are two
Sony monitors, identical models, side by side. They are the same age
in terms of purchase date.
- The Matrox card allows for dual head.
- I use HD-15 cables for both monitors to ensure as many factors as
possible are the same.
- The video artifacts are mostly for vertical objects, eg. straight
dark lines on a light background such as those that can be found along
the edge of a Window. Text is often affected. Here is what it might
look like for one close bracket )))). The further left you go to the
right, the "ghosted" image becomes fainter and fainter.

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"Richard Lee" <r@r.com> wrote in message
news:auela09tbs6it5igq97iekt4rodr3st2n1@4ax.com...
> > It does really sound like classical ghosting. Another possible cause
is
> >termination problems in the
> >video card. What happens if you swap the monitors? Does the artifact
follow
> >the monior, or stay with the
> >system?
> > It may be internal electronics if the artifact follows the monitor.
>
> Appears to follow the monitor. Suppose monitor A was the one showing
> the problem. If I switch the cables around such that monitor A now
> gets its signal from graphics card port B, and monitor B gets its
> signal from graphics port A, monitor A still shows the problem.
>
> What internat electronics? Could being knocked aound during shipping
> be a possible cause? Is this sort of thing easy or difficult to fix?
>
> Some misc notes which you may have already know/figured out:
> - The Matrox video card allows for dual head operation. There are two
> Sony monitors, identical models, side by side. They are the same age
> in terms of purchase date.
> - The Matrox card allows for dual head.
> - I use HD-15 cables for both monitors to ensure as many factors as
> possible are the same.
> - The video artifacts are mostly for vertical objects, eg. straight
> dark lines on a light background such as those that can be found along
> the edge of a Window. Text is often affected. Here is what it might
> look like for one close bracket )))). The further left you go to the
> right, the "ghosted" image becomes fainter and fainter.

Really does sound like its in the monitor - one poster suggested capacitors
on the
CRT neck board - but my experience indicates that more often causes
"smearing",
which is not exactly the same as ghosting.

One more suggestion - if you changed the cables at the card end, now try
changing
the cables at the monitor end. That should eliminate the possibility of a
defective
cable.

Assuming it IS the monitor, I would suspect maybe some internal components
right
near the "front end" of the video chain. Some high end monitors used to use
"T-coils"
to compensate for input impedance changes vs frequency but I don't know
about this
specific one. Perhaps one got moved during shipping. (Can you tell if the
ghosting
happens in all 3 color channels, vs maybe only one?)
Oherwise, maybe the input preamp is not set properly, or perhaps some defect
happened
during shipping to upset the input impedance. An impedance discontinuity is
typically the
cause of ghosting.
If at all possible I'd suggest getting help from the monitor company - it's
not a walk in the
park to follow it down on your own.

HTH

Not Gimpy Anymore

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

I get exactly the same problem, on the same monitor (GDM-F520)...and I
have been doing since I bought it...I thought it may have been my
video card overheating...but since reading this forum, I have decided
otherwise...also because I have a 120mm Delta fan pointing at the
card...

Ive noticed that if I lower the refresh rate of the monitor the issue
appears to be less obvious...but it is still there...also ive noticed
that if I raise the resolution, it becomes less obvious also...

I currently run my monitor at 1280 x 1024 x 32 @ 100hz

id like to run at 120hz but the ghosting does my head in...

I only get the ghosting with black on white...nothing else...dark grey
on white doesnt ghost or any other colour on white...

The 'cancel moire' setting seems to help a bit...

Hope my input helps...

==============
Posted through www.HowToFixComputers.com/bb - free access to hardware troubleshooting newsgroups.

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"tedloon" <peter@teddeh-dot-com.no-spam.invalid> wrote in message
news:40b9cd3c$1_1@news.athenanews.com...
> I get exactly the same problem, on the same monitor (GDM-F520)...and I
> have been doing since I bought it...I thought it may have been my
> video card overheating...but since reading this forum, I have decided
> otherwise...also because I have a 120mm Delta fan pointing at the
> card...
>
> Ive noticed that if I lower the refresh rate of the monitor the issue
> appears to be less obvious...but it is still there...also ive noticed
> that if I raise the resolution, it becomes less obvious also...
>
> I currently run my monitor at 1280 x 1024 x 32 @ 100hz
>
> id like to run at 120hz but the ghosting does my head in...
>
> I only get the ghosting with black on white...nothing else...dark grey
> on white doesnt ghost or any other colour on white...
>
> The 'cancel moire' setting seems to help a bit...
>
> Hope my input helps...
>
> ==============
> Posted through www.HowToFixComputers.com/bb - free access to hardware
troubleshooting newsgroups.

This sounds like further evidence that it really is clssical ghosting -
reflections on the signal cable. As the
refresh rate is increased, the pixel rate is also increased, resulting in
pixel TIMES that are shorter than
the transit time along the cable, which then causes the ghosting to be more
noticeable.
To further the point, try reducing the refresh rate (ignore the flicker if
possible, for the time being) and
see if the ghosting doesn't become less visible, to possible non-existent.

All this demonstrates is that there is a major impedance discontinuity
someplace along the signal path,
at PIXEL frequencies. Many monitor companies used to be guilty of specifying
an imput impedance
and toleerance but never characterizing it at the pixel frequency, which
just happens to be the most
important aspect.

BTW, a discontinuity at the VIDEO CARD end has also been known to have the
same effect.

To solve either typically requires an impedance analyzer that can check
impedance vs frequency
up to and beyond the "video bandwidth" specification of the monitor / card.
Not an easy task.

HTH


NGA

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

er no, I think you're wrong

when I give the monitor a gentle tap on the side, the ghosting
disappears...

I noticed this when I bumped into my desk, and the ghosting
disappeared...

back to the drawing board...

==============
Posted through www.HowToFixComputers.com/bb - free access to hardware troubleshooting newsgroups.

 

[Guest]

Archived from groups: comp.sys.ibm.pc.hardware.video (More info?)

"tedloon" <peter@teddeh-dot-com.no-spam.invalid> wrote in message
news:40c218d1_4@news.athenanews.com...
> er no, I think you're wrong
>
> when I give the monitor a gentle tap on the side, the ghosting
> disappears...

Might this be a sign of an intermittently-bad input connection?

Bob M.

..