Dell UltraScan P990 Focus Drift

[Steve]

I have a Dell UltraScan P990 which has drifted out of focus over the
last 8 years. I know that sudden or drastic focus drift is a sign of
something failing, but this had been a very gradual drift over many
many years and really isn't all that bad, just enough to be a pain.
This monitor has been used for a few hours every day for the last 8
years, (I'm sure there isn't much life left in the tube), so I assume
in this case it is considered acceptable to re-adjust the focus?

Which brings me to my question. The monitor has four access holes on
the back left side for adjustment. Two appear to go nowhere, the
other two go to the two adjustments on the flyback. I however can't
tell exactly which is which, as it is dusty, behing shield, etc.. and
I really don't want to open this one up. Focus is written between the
two adjustment pots. The bottom definantely has a 2 beneath it. I
can't tell if the top has a 1 above it. I've seen flybacks with both
screen and focus, or screen and two focus, but not just two focus (I'm
sure they probably exist, I have little CRT experience). I suppose it
is possible there is a third that is below the holes that I can't see.
Anyway, does anyone know if these are both focus adjustments, or if
not, which is focus? I don't want to accidentally adjust the screen
level.

And, sort of off topic, I know that if you adjust the Anode too high,
the possibility of generating X-Rays can become an issue. Does
adjusting Screen have any safety effect like this, or can it just
reduce tube life if too high?

Thanks,
Steve

 

[Steve]

I have a Dell UltraScan P990 which has drifted out of focus over the
last 8 years. I know that sudden or drastic focus drift is a sign of
something failing, but this had been a very gradual drift over many
many years and really isn't all that bad, just enough to be a pain.
This monitor has been used for a few hours every day for the last 8
years, (I'm sure there isn't much life left in the tube), so I assume
in this case it is considered acceptable to re-adjust the focus?

Which brings me to my question. The monitor has four access holes on
the back left side for adjustment. Two appear to go nowhere, the
other two go to the two adjustments on the flyback. I however can't
tell exactly which is which, as it is dusty, behing shield, etc.. and
I really don't want to open this one up. Focus is written between the
two adjustment pots. The bottom definantely has a 2 beneath it. I
can't tell if the top has a 1 above it. I've seen flybacks with both
screen and focus, or screen and two focus, but not just two focus (I'm
sure they probably exist, I have little CRT experience). I suppose it
is possible there is a third that is below the holes that I can't see.
Anyway, does anyone know if these are both focus adjustments, or if
not, which is focus? I don't want to accidentally adjust the screen
level.

And, sort of off topic, I know that if you adjust the Anode too high,
the possibility of generating X-Rays can become an issue. Does
adjusting Screen have any safety effect like this, or can it just
reduce tube life if too high?

Thanks,
Steve

And, from what I can see the flyback has written on it:
572-11-9407
Hope this helps,
Steve

 

[Eeyore]

This monitor has been used for a few hours every day for the last 8
years, (I'm sure there isn't much life left in the tube)

Why would you assume that ?

Graham

 

[JANA]

In some of these models, there are two focus pots, and one for the screen
bias. The two pots are for both the H and V axis focus. The screen bias
will effect the beam current of the tube.

The poor focus is most likely caused by the age of the tube. Also, it is
possible that the high voltage multiplier has drifted out of spec with age
and use.

You have nothing to loose by messing around with the adjustments and see
where they lead you. Most likely, by the way your description sounds, you
will soon be needing to buy a new monitor anyways.

--

JANA
_____


I have a Dell UltraScan P990 which has drifted out of focus over the
last 8 years. I know that sudden or drastic focus drift is a sign of
something failing, but this had been a very gradual drift over many
many years and really isn't all that bad, just enough to be a pain.
This monitor has been used for a few hours every day for the last 8
years, (I'm sure there isn't much life left in the tube), so I assume
in this case it is considered acceptable to re-adjust the focus?

Which brings me to my question. The monitor has four access holes on
the back left side for adjustment. Two appear to go nowhere, the
other two go to the two adjustments on the flyback. I however can't
tell exactly which is which, as it is dusty, behing shield, etc.. and
I really don't want to open this one up. Focus is written between the
two adjustment pots. The bottom definantely has a 2 beneath it. I
can't tell if the top has a 1 above it. I've seen flybacks with both
screen and focus, or screen and two focus, but not just two focus (I'm
sure they probably exist, I have little CRT experience). I suppose it
is possible there is a third that is below the holes that I can't see.
Anyway, does anyone know if these are both focus adjustments, or if
not, which is focus? I don't want to accidentally adjust the screen
level.

And, sort of off topic, I know that if you adjust the Anode too high,
the possibility of generating X-Rays can become an issue. Does
adjusting Screen have any safety effect like this, or can it just
reduce tube life if too high?

Thanks,
Steve

 

[Andy Cuffe]

I have a Dell UltraScan P990 which has drifted out of focus over the
last 8 years. I know that sudden or drastic focus drift is a sign of
something failing, but this had been a very gradual drift over many
many years and really isn't all that bad, just enough to be a pain.
This monitor has been used for a few hours every day for the last 8
years, (I'm sure there isn't much life left in the tube), so I assume
in this case it is considered acceptable to re-adjust the focus?

They are both for focus. One will change mostly the horizontal focus
and the other the vertical. You need to alternate between them while
looking at a grid pattern. Adjust so that both horizontal and
vertical lines are as sharp as possible.

It's common for monitors and TVs to require focus adjustment after a
few years. Even new ones are rarely set perfectly from the factory.

These monitors don't have a screen control (it's adjusted with
software).
Andy Cuffe

[email protected]

 

[Steve]

Why would you assume that ?

Graham

It's my understanding that CRT's have an average lifespan of
approximately 10000 hours. When I was in college, the screen was on
at least 6 hours a day for four years, and after that it's been on for
at least 4 hours a day, I bought it in 1999, so ~14500 hours. Plus,
the tube has started to slowly fade. I could of course be wrong in my
assumption, it just seems that frequently used monitors don't normally
last 8 years, and if they do the tube probably doesn't have much life
left in it.

Steve

 

[Steve]

They are both for focus. One will change mostly the horizontal focus
and the other the vertical. You need to alternate between them while
looking at a grid pattern. Adjust so that both horizontal and
vertical lines are as sharp as possible.

It's common for monitors and TVs to require focus adjustment after a
few years. Even new ones are rarely set perfectly from the factory.

These monitors don't have a screen control (it's adjusted with
software).
Andy Cuffe

[email protected]

Thanks so much, adjusted them both and it looks nice and crisp again.

Thanks,
Steve