Ultrascan monitor Dell P991

[powerampfreak]

Hi,
This is a Sony Trinitron monitor which I like very much. Its
performance is awesome, unfortunately it has begun giving me picture
troubles. Maybe a year ago, I had to continously decrease screen
brightness and contrast to compensate for the monitor's own increase
of these parameters.
Today I'm using brightness of zero and contrast of say about 20. This
will give me a decent picture. If brightness and contrast are turned
up, retrace lines are seen. Also, the screen when it should be all
black, is more like purple.
This gave me an idea of a too high G2 voltage. But I was amazed when
trying to decrease G2 (on the HVT), this actually changed the focus!
Of course, the focus pot changed the focus aswell. It seems like there
is some short between G2 / focus circuits???
Any advice is appreciated. I'm an electronics engineer of switching
power supplies so you don't need to give any advice like "bring it to
a technician", I'm well into electronics.

Regards
PAF

 

[JANA]

Both the focus and G2 bias are from the multiplier unit. The monitor is
designed to compensate the focus as best possible for the aging of the CRT.
As the CRT ages, its current characteristics change.

There is compensation for the individual electron gun emissions, and also
for the focus voltage to maintain the best possible performance through the
life of the CRT. There will come a time, when this can no longer be
compensated for, because the CRT emission will decrease past practical
limits. At the same time, there is the deteriation of many of the capacitors
in the unit.

From your description, you are dealing with a monitor that has aged
components and a CRT that is starting to go weak.

Check out the new LCD screens. They are incredible, and better for your
health. They have almost zero EMR, no UV radiation, and no X-Ray radiation.
Also, there are no miss-convergence or purity errors.

--

JANA
_____


Hi,
This is a Sony Trinitron monitor which I like very much. Its
performance is awesome, unfortunately it has begun giving me picture
troubles. Maybe a year ago, I had to continously decrease screen
brightness and contrast to compensate for the monitor's own increase
of these parameters.
Today I'm using brightness of zero and contrast of say about 20. This
will give me a decent picture. If brightness and contrast are turned
up, retrace lines are seen. Also, the screen when it should be all
black, is more like purple.
This gave me an idea of a too high G2 voltage. But I was amazed when
trying to decrease G2 (on the HVT), this actually changed the focus!
Of course, the focus pot changed the focus aswell. It seems like there
is some short between G2 / focus circuits???
Any advice is appreciated. I'm an electronics engineer of switching
power supplies so you don't need to give any advice like "bring it to
a technician", I'm well into electronics.

Regards
PAF

 

[powerampfreak]

Both the focus and G2 bias are from the multiplier unit. The monitor is
designed to compensate the focus as best possible for the aging of the CRT.
As the CRT ages, its current characteristics change.

There is compensation for the individual electron gun emissions, and also
for the focus voltage to maintain the best possible performance through the
life of the CRT. There will come a time, when this can no longer be
compensated for, because the CRT emission will decrease past practical
limits. At the same time, there is the deteriation of many of the capacitors
in the unit.

From your description, you are dealing with a monitor that has aged
components and a CRT that is starting to go weak.

Check out the new LCD screens. They are incredible, and better for your
health. They have almost zero EMR, no UV radiation, and no X-Ray radiation.
Also, there are no miss-convergence or purity errors.

--

JANA
_____


Hi,
This is a Sony Trinitron monitor which I like very much. Its
performance is awesome, unfortunately it has begun giving me picture
troubles. Maybe a year ago, I had to continously decrease screen
brightness and contrast to compensate for the monitor's own increase
of these parameters.
Today I'm using brightness of zero and contrast of say about 20. This
will give me a decent picture. If brightness and contrast are turned
up, retrace lines are seen. Also, the screen when it should be all
black, is more like purple.
This gave me an idea of a too high G2 voltage. But I was amazed when
trying to decrease G2 (on the HVT), this actually changed the focus!
Of course, the focus pot changed the focus aswell. It seems like there
is some short between G2 / focus circuits???
Any advice is appreciated. I'm an electronics engineer of switching
power supplies so you don't need to give any advice like "bring it to
a technician", I'm well into electronics.

Regards
PAF

Hi Jana,

But what about G2 adjustment? Why cannot this be adjusted at all?
I realise the automatic focus adjustment, the focus are still perfect.
What concerns me is that I'm unable to change G2.

Regards

 

[Andy Cuffe]

Hi,
This is a Sony Trinitron monitor which I like very much. Its
performance is awesome, unfortunately it has begun giving me picture
troubles. Maybe a year ago, I had to continously decrease screen
brightness and contrast to compensate for the monitor's own increase
of these parameters.
Today I'm using brightness of zero and contrast of say about 20. This
will give me a decent picture. If brightness and contrast are turned
up, retrace lines are seen. Also, the screen when it should be all
black, is more like purple.
This gave me an idea of a too high G2 voltage. But I was amazed when
trying to decrease G2 (on the HVT), this actually changed the focus!
Of course, the focus pot changed the focus aswell. It seems like there
is some short between G2 / focus circuits???
Any advice is appreciated. I'm an electronics engineer of switching
power supplies so you don't need to give any advice like "bring it to
a technician", I'm well into electronics.

Regards
PAF

Go into the color menu and run the "color return" feature. This
should completely fix the problem. Note that it won't let you do this
until it's been on for about a half hour.

That monitor doesn't have a G2 pot. Both of those controls are for
focus. One adjusts the horizontal focus and the other the vertical.
You need to alternate between them until both horizontal and vertical
lines are as sharp as possible.
Andy Cuffe

[email protected]

 

[Andy Cuffe]

Hi Jana,

But what about G2 adjustment? Why cannot this be adjusted at all?
I realise the automatic focus adjustment, the focus are still perfect.
What concerns me is that I'm unable to change G2.

Regards

No monitor has ever had automatic focus.

This monitor's G2 is controlled through software, so there's no
physical G2 control. See my other post about how to fix it without
even opening the case.
Andy Cuffe

[email protected]

 

[powerampfreak]

No monitor has ever had automatic focus.

This monitor's G2 is controlled through software, so there's no
physical G2 control. See my other post about how to fix it without
even opening the case.
Andy Cuffe

[email protected]

Thanks, Andy!

Your advice fixed my problem !! That even without taking the cover
off like you mentioned. Great !!

I won't like the day when this monitor pass away, since I like it very
much. It has very good performance, like you probably know.
By the way, do you have a service manual for it, or more advice
regarding common faults etc ?

Thanks again, Andy!

Regards
PAF