Looking for starting point with monitor problem

J

JM

Guest
I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has been
blurry at the left and right edges of the screen. It also has a wobbling to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a few
hours. I'm trying to get around to getting it looked at somewhere, but I
had the thought recently that maybe these two problems are related, and I'd
like to see what the repair shop comes up with as the cause of the problem.

Is it possible that what's happening is some AC is getting through the power
supply in the monitor, and affecting the scan of the image? It would make
sense (to me) in that case that the problems (blurriness *AND* the shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that the
edges are reasonably clear (as clear as I can get them), but then the centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's not
simply just a tired tube.. the monitor is 5 years old and hasn't seen much
use (sat unused for a few years I was told) so I would hope it's got some
life left still.

Any ideas would be appreciated.
 
Focus problems at the edges along with color bleeding problems are almost
always due to weak picture tubes. Very rarely does a HV regulation issue
cause this problem, but it can.
Only a proper diagnosis by someone with lots of experience troubleshooting
monitor problems without schematics will you be able to find out the true
cause of the issue.

David

JM <jmsn@ns.ns.sympatico.ca> wrote in message
news:Zs%Jb.51675$IF6.1127105@ursa-nb00s0.nbnet.nb.ca...
I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has
been
blurry at the left and right edges of the screen. It also has a wobbling
to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a few
hours. I'm trying to get around to getting it looked at somewhere, but I
had the thought recently that maybe these two problems are related, and
I'd
like to see what the repair shop comes up with as the cause of the
problem.

Is it possible that what's happening is some AC is getting through the
power
supply in the monitor, and affecting the scan of the image? It would make
sense (to me) in that case that the problems (blurriness *AND* the
shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would
be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that the
edges are reasonably clear (as clear as I can get them), but then the
centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's not
simply just a tired tube.. the monitor is 5 years old and hasn't seen
much
use (sat unused for a few years I was told) so I would hope it's got some
life left still.

Any ideas would be appreciated.
Click to expand...
 
Thanks. If I do get it looked at I'll post the results.

"David" <dkuhajda@locl.net.spam> wrote in message
news:3ff8dbf8@news.greennet.net...
Focus problems at the edges along with color bleeding problems are almost
always due to weak picture tubes. Very rarely does a HV regulation issue
cause this problem, but it can.
Only a proper diagnosis by someone with lots of experience troubleshooting
monitor problems without schematics will you be able to find out the true
cause of the issue.

David

JM <jmsn@ns.ns.sympatico.ca> wrote in message
news:Zs%Jb.51675$IF6.1127105@ursa-nb00s0.nbnet.nb.ca...
I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has
been
blurry at the left and right edges of the screen. It also has a
wobbling
to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a
few
hours. I'm trying to get around to getting it looked at somewhere, but
I
had the thought recently that maybe these two problems are related, and
I'd
like to see what the repair shop comes up with as the cause of the
problem.

Is it possible that what's happening is some AC is getting through the
power
supply in the monitor, and affecting the scan of the image? It would
make
sense (to me) in that case that the problems (blurriness *AND* the
shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would
be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that
the
edges are reasonably clear (as clear as I can get them), but then the
centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the
problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's
not
simply just a tired tube.. the monitor is 5 years old and hasn't seen
much
use (sat unused for a few years I was told) so I would hope it's got
some
life left still.

Any ideas would be appreciated.
Click to expand...
 
As for your focus problem, this is the CRT most of the time. Or, there may
be a dynamic focus problem. The HV module would be most likely the fault in
this case, if it is not the CRT.

The wobbling effect can be from the power supply, scan circuits, pin amp
sections, or there are some stray magnetic fields near to the monitor. You
should first verify the power supply performance for voltage using a DVM,
and hum and noise using a scope.

Because the focus gets better at lower contrast, this is a very strong
indication of a weak CRT. If there is a dynamic focus fault, the focus would
be more stable with screen brightness changes. All of this has to be
properly checked.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"JM" <jmsn@ns.ns.sympatico.ca> wrote in message
news:Zs%Jb.51675$IF6.1127105@ursa-nb00s0.nbnet.nb.ca...
I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has been
blurry at the left and right edges of the screen. It also has a wobbling to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a few
hours. I'm trying to get around to getting it looked at somewhere, but I
had the thought recently that maybe these two problems are related, and I'd
like to see what the repair shop comes up with as the cause of the problem.

Is it possible that what's happening is some AC is getting through the power
supply in the monitor, and affecting the scan of the image? It would make
sense (to me) in that case that the problems (blurriness *AND* the shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that the
edges are reasonably clear (as clear as I can get them), but then the centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's not
simply just a tired tube.. the monitor is 5 years old and hasn't seen much
use (sat unused for a few years I was told) so I would hope it's got some
life left still.

Any ideas would be appreciated.
 
One thing I didn't mention, which makes me think it may not be the CRT, is
that the focus is very good at first, when I first turn the monitor on, and
seems better longer when the ambient temperature is low.. Would temperature
affect a weak CRT in this way?

"Jerry G." <jerryg50@hotmail.com> wrote in message
news:btas67$qms$1@news.eusc.inter.net...
As for your focus problem, this is the CRT most of the time. Or, there
may
be a dynamic focus problem. The HV module would be most likely the fault
in
this case, if it is not the CRT.

The wobbling effect can be from the power supply, scan circuits, pin amp
sections, or there are some stray magnetic fields near to the monitor. You
should first verify the power supply performance for voltage using a DVM,
and hum and noise using a scope.

Because the focus gets better at lower contrast, this is a very strong
indication of a weak CRT. If there is a dynamic focus fault, the focus
would
be more stable with screen brightness changes. All of this has to be
properly checked.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


"JM" <jmsn@ns.ns.sympatico.ca> wrote in message
news:Zs%Jb.51675$IF6.1127105@ursa-nb00s0.nbnet.nb.ca...
I have an HP 21" Trinitron monitor (HP A4576A). Since I got it, it has
been
blurry at the left and right edges of the screen. It also has a wobbling
to
the display, most noticeable at either edge, whenever I have the refresh
rate set to something other than 60 hz, and it's been turned on for a few
hours. I'm trying to get around to getting it looked at somewhere, but I
had the thought recently that maybe these two problems are related, and
I'd
like to see what the repair shop comes up with as the cause of the
problem.

Is it possible that what's happening is some AC is getting through the
power
supply in the monitor, and affecting the scan of the image? It would make
sense (to me) in that case that the problems (blurriness *AND* the
shaking)
both go away at 60hz, since I have 60hz AC. The other possibility would
be
some EM interference, but I've tried the monitor at different angles, in
different rooms, and connected to different sources, and it behaves the
same.

I've been able to make the image decent by adjusting the focus so that the
edges are reasonably clear (as clear as I can get them), but then the
centre
starts to bleed. This can be minimized by dropping down the contrast
though. Maybe this points to something else as the cause of the problem.
In any case, it always seems to look great at 60hz, so I"m hoping it's not
simply just a tired tube.. the monitor is 5 years old and hasn't seen
much
use (sat unused for a few years I was told) so I would hope it's got some
life left still.

Any ideas would be appreciated.
Click to expand...
 
Is this by chance a "Made by Sony" monitor ?
I have had some problems with 17" Dell/Sony monitors that developed
problems like you describe. Adjust focus for good center, and the sides would
be out of focus. Adjust for sides and the center would be bad.

It turned out that a small transformer in the dynamic focus circuit had
small cracks in the core (around the transformer). Replacing the transformer
fixed the problem. It was located just in front of the heat sink that is
around the flyback.
Hope this helps....
John
 
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