Cause of blank screen, otherwise normal operation?
I suspect the display has died but does anyone have any suggestions on things to check to fix an imac screen?
The diagnostic LEDs are showing
1. Lit when connected to the mains
2. Lit when machine is running
3. Lit when machine is running
4. Not lit when on or off.
The machine starts and runs and outputs to an external monitor but its internal display is completely dead. No backlight or anything.
This occurred after a failed hard disk was DIY replaced, the mainboard to display cable was damaged and replaced during this operation - is there a way to test the display or confirm that a particular component is defective in the chain? The mainboard display connector seems ok, all its pins look visually ok, the vsync lead is ok, the temp lead also ok and the power (I think) lead from the video adapter inverter is also ok.
Be good to know where to investigate even if its only to know which bits cannot be sold on as spares. I'm perplexed as to the display led #3 reporting that its ok even though its not showing a picture, unless the picture is being sent but the display isn't powering up to show it?
I'm testing it without a hard drive in case this makes a difference. I do get the start up 'chime' and I've reset the pram and pulled the cmos battery (2.9v) and left overnight. But to no, unsurprising, effect. Its an a1311 model.
Any pointers appreciated,
Is dit een goede vraag?
66 
68 
359 
3 opmerkingen
Hi Dan,
No display at all, I had thought of waiting till tonight and seeing if there is any image at all when its pitch black. The screen gives no indication of life at all though, no flicker or anything. the damaged cable is at work, pretty much mangled the logic board end connector, the socket does seem ok though. I'd half expect the backlight to be on and just mess on the screen if this connection was bad though? re: shorting the cable, the whole thing had been powered down and was unplugged when we attempted the repair, I'm not sure we could have caused this level of broken?
cheers,
toby
door toby
Hi machead3,
Ah sorry, I've read quite a few guides on this sort of imac and have probably gotten the diagnostic arrangement muddled with something else. If #4 is the screen one then it does confirm the OBD knows somethings up. The invertor board (besides PSU) seems ok, nothing burnt and the sockets and cabling seem fine. does it give an indication that its alright via some onboard surface mount LED or does it just not work? I don't really see how the inverter could be incorrectly installed though :)
would you suggest that one is more suspect that the other - given there is no backlight and no image does that point more at the invertor no supplying the screen or the screen just being completely dead?
cheers
toby
door toby
I'm getting ~7v (DC) across the two pairs running from the inverter to the display in case that's important?
door toby