8 Replies Latest reply: Dec 6, 2012 1:07 PM by Windowssonic
Windowssonic Level 1 Level 1 (0 points)

I Bought a Imac g3 (1998) Orange at a thrift store yesterday and it has been having Screen Flicker problems. The first day I used this computer it was working fine, until the next day when the screen (Keep in mind i was using it) started to flicker at about a hour of usage. I unpluged the system, and then unpluged everything else. I readed other messages and one said it might interfear with the cables, and to turn down the sound. I could not turn down the sound beacuse the IMac could not let me. I was running the system with extentions OFF, beacuse the system was missing a Itunes MPEG extention, so thats why. Thank you if you could help me. Can you maybe tell me where to get the itunes Mac OS 8 MPEG extention, too?

IMac G3 (Original) , Mac OS 8.6 or Earlier, No other details
  • rccharles Level 5 Level 5 (6,650 points)

    All of the iMac g3's have screen problems.  It was the era of bad capacitors. The iMac g3 models a,b,c, & d had an internal fan.  Verify that it is working.  The repair of CRT's is a lost art.


    The problem could be heat related. You could try increasing the air flow. Try putting a fan below & direct the airflow up.


    You could look on ebay for Mac OS 9.x.  Make sure you get the full install version .  A large gold 9 on the cd & box.


    You might want to look for another cheap machine.  You would be better off with a newer machine.  Look for a mac mini.


    I readed other messages and one said it might interfear with the cables,


    I would think that this would show up when you started the machine & not after it ran for awhile.


    I recall that placing headphone in the head phone jack turns off the speaker sound.  I think that a dummy jack turns off speaker sound too.



  • Windowssonic Level 1 Level 1 (0 points)

    I knew the fan was working beacuse  I put my ear up to the matchine and it was loud and working. And how do I know mine is model a,b,c, or d? Also, when I turn off the screen, it makes a weird sound, like if it were on fire. and so I just put a fan in there up so the airflow would go up? Im still a little confused.

  • rccharles Level 5 Level 5 (6,650 points)

    iMac g3

    a -- 233 2mg vram

    b -- 233 6mg vram

    c -- 266

    d -- 333


    Query by serial number

    "A serial number is a unique, identifying number or group of numbers and letters assigned to an individual piece of hardware or software. It's used for various things depending on the product / brand but what is your Mac's serial number for and more importantly... what is it hiding and what can it do for you ?"





       ( hint by K Shaffer  )


    I think that you have a capacitor problem.  The power off sound is an indicator.


    You could try cooling your iMac some more. 


    How to fix iMac capactor problem.





    What are you wanting to accomplish  with this machine?  Is it a hobby machine?


    I'd recommend at least a G4 processor & 1ghz.  Most people would say an early intel processor Mac.



  • Mac Man JW Level 2 Level 2 (170 points)

    That sound is a bad flyback transformer the flyback transformer is what makes the hi voltage for the monitor to work and would make the screen flicker if it is going bad. I just got 5 of the tray loading imacs that have this issue if yours makes a hissing nose when off i am %100 sure it is the flyback transformer

  • Windowssonic Level 1 Level 1 (0 points)


    Now, after about 5 months of it being off, i started it up again. It did the same problem, but even faster (about one flicker every 1 second) and now i turned it right off beacuse i was afread that if it went on longer, it would of just gave out. Can you find me a place were i can get a Fly Back Transformer. And it does hiss when it flickers. Can i get a Fly Back Transformer off ebay? were should i get it? how do i replace it?

  • Windowssonic Level 1 Level 1 (0 points)

    i nodiced that the FBT is on the analog board... Found one on ebay but its for 2000-2001 models- mines 1998

  • Mac Man JW Level 2 Level 2 (170 points)

    I think this is the right Flyback You will have to open it up and cheek the #'s on the flyback. This persion from this thread http://forums.macrumors.com/showthread.php?t=1304637 (post # 18) ordered one for his imac and it worked ok! but remember CRT's can hold Power even when off so make sure you know what you are doing before you open it


    Ebay Link to flyback transformer http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=290595654328&ssPageName=A DME:X:RTQ:US:1123

  • Windowssonic Level 1 Level 1 (0 points)

    Do i half to change it? Is there a more simple solution? Some please respond beacuse i want to use my IMac again soon as possible.