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annoying dot in the image

Discussion in 'Projectors, Screens & Video Processors' started by dprior, Dec 15, 2002.

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  1. dprior

    dprior
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    Firstly

    Hello to all here (it's my first post) and thanks for supplying a wealth of useful info. I've been reading threads here for maybe 8 months and was drawn to the world of CRT. I have a Sony 1271 which I am very happy with, at least until I save a few grand for an upgrade.

    Anyway, I now have a small problem.

    In the last few days a small dot has appeared in the red tube image. It is about the size of 1 pixel, and idoes not light up. so the dot looks black with only the red tube projecting. Apart from the dot the PJ works perfectly.

    Unfortunately, the dot is just off centre so appears in the middle of faces quite often. Since skin uses red, the dot becomes obvious as it shows up blue/green.

    Any ideas what has caused this, if it is fixable and how do I prevent it happening again.


    ALSO, on a slightly different note.

    When I mounted the PJ on the ceiling and set about positioning the image and re-converging etc. I noticed that with the adjustment set at the middle position the image is twisted on the tube face. It is not distorted but just twisted. I have to set the horizontal and vertical skew to max on one tube and maybe 90% on the other two to get the image almost level.

    If anyone can shed some light I would be delighted.

    Thanks



    :confused:
     
  2. Roland @ B4

    Roland @ B4
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    The mark on your red tube is permanent I'm afraid. If it was in the middle then I would suspect some scanning failure but with it being off centre I think you just have a blemmish on the tube surface which has probably been there since new. The only fix is to repalce the tube.

    The twisting of the image can be ajusted by twistig the deflection yokes. This has to be done with the projector on and displaying a grid. It shouldonly be done with the settings to mid position. You have to get your hand very close to the EHT circuits so be careful.
     
  3. beta

    beta
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    I have only seen it when someone tries to convert from floor mount to ceiling or vice versa and they only change the HV on one or two of the tubes and not all three at once, then you get a beam so strong it physically punches a hole in the phosphor, like on the attached pic of a green tube that I actually de-fungused on a 1041 ;) But this tube has it really bad, I did see it on a red tube on a 1000qm but that was like 3 small dots about top centre going down vertically to almost middle of the tube face


    My HS10 LCD and 1251 CRT stuff

    Rowland, do you know if 07MP tubes can be rebuilt? ohh master of crt :)
     

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  4. dprior

    dprior
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    Thanks for the replies.

    I can't remember seeing the dot at the start but maybe it was there. When the PJ was sitting on a table, perhaps the dot typically fell lower than head height, so maybe i just never noticed it (eyes alwas focus on the face). I watched a film tonight and I only noticed it a couple of time in the two 2 1/2 hours so it's not really that distracting.( plus I know its there so I inherently look for it!!)

    Is there a rule for switching CRT PJs on?? I use a HTPC to send all signals to the PJ, should I wait until the PC is fully booted before starting the PJ?? If the PJ is on when the PC starts, the projector image rolls when power strip changes the screen resolution, until it re syncs to a stored block setting.. Could this 'switching' signal posibly cause a burn on the tube???
     
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