Failure to boot - white screen

[admwright]

Hi,

Our iMac 6,1 is failing to start. I have tried the following and am not sure what to do next. Any suggestions?

1) reset VRAM, no change
2) boot from original cd and run hardware test. No problems found
3) boot from original cd holding down c. Tries to load from cd then get message "you need to restart your computer. Hold down the power button for several seconds or press the restart button. After restart and booting from cd just get same message
4) boot and hold option key select to boot from external backup boot disk - apple logo and circle then white screen.
5) boot and hold shift key - tries to enter safe mode but just get a white screen with a blue mouse pointer in top corner

Any help appreciated
Andrew W.

 

[FreemanW]

My speculative sense is (regardless of the AHT negative return) the hdd has failed.

 

[admwright]

If the internal hard disk fails can you not then boot from the cd or an external hard disk? I have tried both of these and I always end up at a blank white screen. Not saying it is not the hard disk, but possibly something else is wrong as well?

All the best
Andrew W.

 

[h9826790]

Did you try a SMC reset as well?

 

[admwright]

Did you try a SMC reset aw well?

No, missed that. I will try it tonight.

Actually picked up a Mac Mini and got it set up from the time machine backup - very painless. Once it was running I connected the iMac to it in target mode and the iMac hard disk shows up fine. Used Disk Utility to check and repair permissions but did not change the boot failure. Definately some other hardware issue. Screen works, DVD works, hard disk works, just does not boot. Looks like last chance is the SCM reset?

Thanks
Andrew W.

 

[h9826790]

One more question, did you perform a complete RAM test in AHT?

A quick test may not able to pick up the RAM error which likely will cause a failure to boot.

 

[admwright]

One more question, did you perform a complete RAM test in AHT?

A quick test may not able to pick up the RAM error which likely will cause a failure to boot.

Yes, I selected the 'full' test when running the AHT.

 

[RV12Pilot]

Video

I am no way an expert....but I had the "white" screen issue. It was my video card/chip/? I went to authorized repair center and they fixed me up quickly. Was very interesting to watch them take apart an IMAC to work on. My video lasted just over three years.

 

[admwright]

Did you try a SMC reset as well?

Looked up the SMC reset - this is just unplugging the iMac waiting a bit and plugging back in then switching on? I have done that without knowing it resets, the iMac has been shut down and no power many times over the last few days! Looking more and more like some hardware issue that the AHT did not detect.