Connect with us

Dell UltraScan P990 Focus Drift

Discussion in 'Electronic Repair' started by Steve, May 23, 2007.

Scroll to continue with content
  1. Steve

    Steve Guest

    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
     
  2. Steve

    Steve Guest

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

    Eeyore Guest

    Why would you assume that ?

    Graham
     
  4. JANA

    JANA Guest

    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
     
  5. Andy Cuffe

    Andy Cuffe Guest


    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

     
  6. Steve

    Steve Guest

    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
     
  7. Steve

    Steve Guest

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

    Thanks,
    Steve
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-