1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

dirty screen on JVC

Discussion in 'Televisions' started by cypher007, Jan 17, 2005.

  1. cypher007

    cypher007
    Active Member

    Joined:
    Jan 2, 2005
    Messages:
    415
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    19
    Ratings:
    +11
    ive noticed if i use my PC with a white backdrop for a while, that kind of muddy patches appear. if i then switch back to normal tv these will slowly disapear. is this dirty screen?
     
  2. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    Hi, difficult to diagnose at a distance. I guess what you're saying is that if you display the output of your PC on your JVC telly with a mainly white picture after a while the white areas of the picture become 'dirty' ie, they are no longer pure white ? If you then select a 'normal' tv picture everything returns to normal after a while ?

    If that is what you are describing then it seems to me that what you are describing is 'excessive beam current'. It sounds as though the drive signals from the PC are too large causing the crt to try and deliver a brighter than normal white picture. In layman's terms this causes the crt to try and deliver excessive electron beam current to the crt - this excessive beam current heats up the shadow mask causing it to distort - this gives rise to beam landing accuracy errors and the displayed result is slight purity errors - not enough to actually cause 'classic' purity errors (ie, areas of incorrect colour) but enough to cause a loss of beam landing efficiency and a reduction in light output - hence why it appears to be 'muddy'. When you then return to a conventional tv picture the beam current reduces and the shadow mask cools down a bit and returns to its 'normal' mechanical size/position. Now, inside a tv there is circuitry to prevent this condition happening - the beam current should be limited - so it sounds as though either your telly doesn't have this circuitry (highly unlikely) or it is misadjusted. As you'll appreciate it's not normal for a domestic tv to display a white raster for a long time.

    You should be aware that if my diagnosis is correct then if the telly is persistantly 'driven' in this condition then there is a possibility that the shadow mask will permanently distort and you will then have a permanent problem - I suggest you try and check the signal levels arriving from the PC or take steps to avoid outputting a mainly bright white picture. Regards, yt.
     
  3. nig28

    nig28
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hi
    This is also made worse by the brightness/contrast being set too high.
    Nigel
     
  4. cypher007

    cypher007
    Active Member

    Joined:
    Jan 2, 2005
    Messages:
    415
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    19
    Ratings:
    +11
    what i find is the tv even on soft picture mode seems to try and burn your retina out. maybe this and the other probs ive got means ive a friday special?
     
  5. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    I'm afraid I don't know what 'soft picture mode' is since I'm not familiar with your tv set - my comments were more for general interest. If your tv gives a 'good' picture when viewing a conventional tv channel (or source such as DVD) then I suspect that you should look at the output of the PC. JVC is a reputable make and I would like to think that your tv set has been properly set up before leaving the factory. I wonder too if maybe you have the contrast set too high ? (as Nig28 suggests) Although the tv set should obviously give a nice bright picture it shouldn't be so bright as to cause you discomfort (even close up in a darkened room). Regards, yt.
     
  6. cypher007

    cypher007
    Active Member

    Joined:
    Jan 2, 2005
    Messages:
    415
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    19
    Ratings:
    +11
    i find on soft mode the contrast sets to about 1/3rd, and thats still very bright.
     
  7. skybluescooby

    skybluescooby
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hi, a late post but a relevant one. I have had this problem with my set since purchase on Nov 04, the set has barely been in my house and has spent mich of its life in the service centre as (powerhouse) refused to exchange it.
    Now i've had three new cases, and a new tube fitted which i had hoped would cure the problem, the guys in the service centre mentioned the mask and contrast settings but even when the contrast is reduced the picture blur is still evident.
    I have sky plus and it is really noticable when light colours are displayed or even when the red BBC screen comes on,
    This is now the second tube and I'm wondering why this is happening.
    The second tube is showing signs of the same thing happening as the "muddy patches" start of small then after a while the whole screen becomes blurred.
    Any new ideas on this topic ??
     
  8. hornydragon

    hornydragon
    Well-known Member

    Joined:
    Dec 19, 2001
    Messages:
    28,293
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Somewhere near the M4 most of the time......
    Ratings:
    +1,215
    JVC's do have brightness issues, normally too dark and brightness needed uping in service menu perhaps a search will reveal some more info i think it was X4 sets (none dist 100Hz with component input) that werent bright enough...
     

Share This Page

Loading...