Imac a1312 late 2009 problem

[tonvanrijn]

Need help, imac fails most of the time. Always start sound, sometimes white start screen, sometimes full startup, most of the time white screen than black and hd continues to sound like starting up but screen stays dark. Which part of the computer is the most likely failing part with this behaviour?

 

[grwren]

Hi. I'm new to imac's (just inheratited a similar model) but not totally new to computers and my first guess might be the hdd. After all it is ten+ years old and it may be experiencing some problems. If you can get the thing booted up reliably you might want to go to the following link and check the hard drive: https://osxdaily.com/2012/05/24/check-hard-drive-health-mac-disk-utility/. I'm sure there are other drive test for macs but this is the only one I'm currently familiar with. If the hdd passes the test then it's probably something else and I doubt I can help you there.

Alternatly, if you can get the thing up and running reliably for a while, or get your hands on another computer, you might want to research how to make a live boot usb drive (or dvd) of the macos, or some other os like linux or windows, your choise, and see if it will live boot reliabiliy. That way you've totally eleminated the imac hdd from the picture.

Anyway, good luck!

 

[philipjj61]

Get a strong torch after startup and shine into the screen at an angle if you can see a very dim desktop it may be the backlight board the power supply or the connections between. Plug in an external monitor or tv into the mini dvi port with a suitable adaptor to diagnose GPU circuits/board(and/or give an extra monitor). Software may be responsible so backup and do a "clean" install. Go through the Reset procedures for PRAM reset and SMC reset for your model first as they are easy.