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iMac G4 root problem

reddrag0n

reddrag0n

macrumors 6502a
Original poster
Oct 1, 2007
637
173
Canada
I was wondering if anyone could tell me what my poor iMac is doing.

I bought it off of Kijiji and when it was demo'd before i bought it, it was working fine. Once i got it home and turned it on, i got this on my screen...

IMG_0004.JPG


I turned it off, let it sit overnight, and then turned it on again. This time instead of those lines, it fades from black to green then to a bright white.

I am able to turn up and down the brightness via the keyboard *F14 and F15 keys* but that's all i can do. I don't see anything on the screen other than bright white.

Is this a problem with the onboard graphics, or is it something else?
 
Can you hook up an external monitor to the mini vga port?

Most likely, the on board video is bad, but hooking up an external monitor will confirm that for you (and rule out just a bad lcd display/video cable/ect).
 
Is it possible to test it on an external monitor? That way if it displays fine on the external monitor it's most likely a loose connector or possibly the LCD itself.

If it doesn't display ok then it's graphic card related.

Edit - Beat by a minute..
 
Sure, if you can loan me an adapter to test that theory. since all the stores here in Edmonton don't carry the mini-vga to vga adapter.
 
Intell: As for moving the screen, yes, tilted it, moved it up and down, almost broke the neck because i moved it around so much, and no, still the same issue

Nameci: Would that be the cable labeled TMDS?
 
reddrag0n said:
Intell: As for moving the screen, yes, tilted it, moved it up and down, almost broke the neck because i moved it around so much, and no, still the same issue

Nameci: Would that be the cable labeled TMDS?
Click to expand...

Yes, the internal video cable on G4 iMacs is called the TMDS cable. If the on screen images didn't change, then that cable probably isn't to blame.
 
I have read on some of the apple forums that the inverter board might be to blame, but it still has brightness control. I have ripped apart the lcd unit and found 4 cables that connect to the inner area.
1 - TMDS cable, 2 - the mic cable, 3 - the power light cable, 4 - both inverter power cables. I double checked all of those and still no change. So far it's boiling down to one thing, the logicboard. If i replace this, can i also go a step up in cpu speed too? Am not sure if the 700 and 800 MHz models were identical for those years.
 
reddrag0n said:
I have read on some of the apple forums that the inverter board might be to blame, but it still has brightness control. I have ripped apart the lcd unit and found 4 cables that connect to the inner area.
1 - TMDS cable, 2 - the mic cable, 3 - the power light cable, 4 - both inverter power cables. I double checked all of those and still no change. So far it's boiling down to one thing, the logicboard. If i replace this, can i also go a step up in cpu speed too? Am not sure if the 700 and 800 MHz models were identical for those years.
Click to expand...

The 700 and 800Mhz boards are the same, but are different from the 1 and 1.25Ghz boards.
 
Ok, so i can easily get an 800 MHz iMac G4 board with the onboard Geforce 2 MX graphics. That's good to hear.

I just restarted the iMac and the same thing with the display is happening again. The fading from black to green then to a bright white.

I will post a few videos showing that it works, but not the screen.
 
Well, the iMac is running, updated to the latest 10.4.11 via VNC and now this is what i am seeing on the screen. It looks like girl stripes!!!

IMG_0008.JPG


Yeah, i think the graphics chip has given up the ghost
 
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