iMac G3 Crt screen issue (rainbow affect+ dimmed out)

Discussion in 'PowerPC Macs' started by TheAppFinder, Apr 11, 2010.

  1. macrumors newbie


    Oct 1, 2009
    Hi, I have an iMac G3. The specs are:
    600 MHz G3 /Graphite
    1 GB RAM
    40 GB HDD
    Mac os x tiger 10.4

    Here are the 2 problems with the screen/ crt:

    The problem with the screen is that it's not as good, as it used to be. I have another g3 imac (450 MHz Sage) and my dad pointed out that the sage imac's display is much more sharper then my 600 mhz graphite. And i had a look at at it and my dad was right. Also their are lines going down the sides of my screen (which you can barely notice on the sage imac) is their a way to fix this? Thanks.

    Also another problem i have with the screen is that I am seeing rainbow affects on the screen. I read online that the anti-glare film/coating is scratched (but thats with different crt monitors eg sony 21" etc) Is their a way to fix that as well? Just today I noticed more and more showing up! (or is it just me!) :eek:

    Any help would be great! Thanks! :)
  2. macrumors regular

    Apr 9, 2010
    Oklahoma City
    CRT lifespan

    CRT monitors are rated for approximately 25,000 to 30,000 hours of use. So if your CRT monitor is on for an average of 8 hours a day, it should last roughly 10 years before you notice a drop in its brightness. You machine is roughly 9 years old so it sounds like just your average CRT aging. The good news is you are getting closer to a new iMac.
  3. thread starter macrumors newbie


    Oct 1, 2009
    Most of the time I'm at school and so my mac is usually in sleep mode, and so i only use it for 3-4 hours a day. And i use it as my main machine because i am selling my pc (which is from the same time as my imac :) ) Its got ilife 04 on it and many other porgrams!
  4. macrumors 68040


    Sep 17, 2009
    1 .)dimmed effect less sharp

    if you experience that the colors of the screen are a bit dull (pastell)or pictures /letters appear not sharp enough ,
    and changing settings in "system preferences>displays>colors "give no results

    there is another way of brighten /sharpen up the screen again
    first choose a wallpaper that displays a picture ,best i found for that is the fur of the cats you are using (panther, tiger)in the "system preferecnes >desktop/screensaver >desktop >nature "as its very detailed with single hairs to spot ,
    now go to
    "system preferences>displays>colors "and chose iMac as color setting , done now shut down and unplug it

    open the bottom part of the case (easy done , leave the metal shielding where it is)
    lay your iMac on the usb port side (leave the mouse plugged in if you want to try another picture )
    now you will spot on the side facing upwards direct opposite the usb ports two plastic screws ,they are for screen adjustment
    plug it back in and boot up ,now play with the screws until you can really spot every single hair on the fur and get the colors bright again

    it worked fantastic on mine the brightness and sharpness is back again, the colors are really bright again , it feels like i would have a new screen

    2.) rainbow colors surrounding the screen

    sollution : your monitor doesn't demagnetize as it should
    you can force it , on near the usb ports you see two buttons one has a triangle on it ,press it , thats forcing a restart and should trigger the demagnetizing you should hear a klick from the back of the iMac , if its still rainbow colored , repeat as often until the rainbow colors disappear ,
    dont know why it does not demagnetize after a couple years, but it worked on mine and after a couple days with this cruel practice niow its fine again and is demagnetizing on its own and no more rainbows surrounding the screen
  5. thread starter macrumors newbie


    Oct 1, 2009
    Thanks for the really detailed explanation! But for the rainbow affect, its not the large colors you usually see. (you can get these colours by holding a magent by the screen! did it when i was little!) Its the little ones, like the ones you see when you get a liquid on the display (eg after you sneeze all over the screen, you get the little rainbow affect from the salyva (hope i spelled it right :p lol) or when you touch it with your fingers and it sometimes leaves a smudge of colours!

    And also if it's not much trouble for you could you make a video showing how to fix the dimness of the screen? thanks! I learn better by video for some reason! :)
  6. thread starter macrumors newbie


    Oct 1, 2009
    Does it look like this?

    Attached Files:

  7. macrumors 68040


    Sep 17, 2009
    yes they look exactly like that :)
    these two little platic screws create wonders :)
    have no video camera so cant make a video :(
  8. thread starter macrumors newbie


    Oct 1, 2009
    Which screw?

    So do i adjust both screws or just only one of them? 
  9. macrumors 68040


    Sep 17, 2009
    both screws until you got the perfect picture again :)
  10. thread starter macrumors newbie


    Oct 1, 2009
    So, I have to make sure the display profile settings are set to: imac? right. Why can't i use adobe rgb? (which is what i'm using right now? ) Thanks! 
  11. macrumors 68040


    Sep 17, 2009
    adobe rgb is dark
    the original "iMac" setting is about in the middle of the others in terms of brightness , thats why its the best setting to set up the monitor
  12. thread starter macrumors newbie


    Oct 1, 2009
    Oh! and i forgot one other thing. when i increase or decrease the volume and it gives the feedback by sound and on the screen, it shows the things on the screen that i cant normally see. for example. if their is a website and their are lines separating and ad (for example) and i don't see it, but then i want to lower the volume, and then the line appers, but then goes away cause the feed back is done.

    So after i play around with the 2 screws on the flyback transformer, will it show websites in greater detail, and will the 2 lines that are on the edge of my screen go away? and finally after i play with the 2 screws, can i go back to adobe rgb? Thanks for your help! :)

    (ps. i get really nervous when i open my imac for some reason! :p
  13. macrumors 68030


    Jan 11, 2007
    I'd read this before opening that iMac...

    I've seen too many people get belted by TVs / Monitors that "were unplugged for at least a day!"

    The screws you need to adjust, are on the exact component responsible for said belting.

    Good luck.
  14. macrumors 68040


    Sep 17, 2009
    yes your screen should be bright and detailed again after screwing around :)

    what browser are you using ? try camino for G3
    best for the g3 iMac's

    and reset pram might help too

    dont be afraid of the high voltage the screws are plastic and if you use a insulated screwdriver there is no chance of getting belted
    you only open the bottom ..these screws are there to be able to adjust the screen :)
  15. macrumors regular


    Feb 5, 2007
    One bad move around that flyback & all your troubles will be over :eek:

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