Is my LCD toast or is it my power supply?
UPDATE 1: When I boot the computer up with the external display connected and powered externally, AND with the ribbon connector plugged into the built-in LCD, but NOT the 12-pin inverter cable I can see, with a flashlight, the working desktop on the built-in LCD.
UPDATE 2: I was able to get an LM240WU2 LCD (that I was assured was working - can't vouch for that though) and popped it in my iMac. This resulted in the exact same problem as before: halfway through the startup chime the computer powers down. No picture is seen on the LCD.
When I press the power button on my iMac it begins to start up, but halfway through the start chime it loses all power and needs to be unplugged before the power button can be pressed again. The screen always remains black.
What I have figured out so far:
1) First diagnostic LED is lit. Upon pressing power button second LED lights up, but halfway through the startup chime the third LED lights momentarily then the whole thing dies completely leaving no LED lights on until I unplug it and plug it back in.
2) iMac will boot up and run with the LCD completely disconnected, but not with it connected.
3) When an external display is connected the iMac starts up and runs reliably. External screen shows picture, but the display can't display all colours, only blues and yellows.
Is it possible that the power supply no longer has enough power to start up the big LCD but runs everything else fine? Or is it more likely that the LCD screen is the culprit considering the little bits I can hear in it?
I have had this happen twice before, and both times, after many restarts everything booted up again and ran for another 4-5 months before happening again.
Is this a good question?
3 Comments
When booted and using the external display can you discern the desktop on the iMac by shinning a flashlight at an angle on it?
by mayer
Mayer: As I'm sure you know, you're onto something! So, I just booted the computer up with the external display connected and powered externally. I also plugged the ribbon connector into the built-in LCD, but NOT the 12-pin power cable. As you suggested I can see, with a flashlight, the working desktop on the built-in LCD. Is it the backlight? I have certainly run this thing practically 24/7 for 6.5 years!
by Mike
I have this same problem and looking below it would seem as of this comment Mike's problem is not quite solved. I'm new to this forum so not quite sure if this is right way to go about it but I have posted the info I have gathered in an answer below and hope that someone might be able to provide some insight. Thanks
by Da Hooligan