iMac "green light of death" revisited. Any Mac hardware techs out there?

[diehlr]

I've got an old Bondi rev. A iMac that is suffering from the "green light of death" syndrome. In other words, when shutting down or restarting the computer, the monitor light stays green instead of switching to orange/amber and flicking back over to green again. The consequence being the monitor doesn't turn back on. After unplugging the power cord and plugging it back in, it comes up fine 100% of the time.

I've been doing research on this issue and most people point to a faulty analog video board on the monitor. Specifically, the flyback transformer on the back of the CRT neck. I don't believe this is a valid explanation for these symptoms, since the machine will come on just fine when power cycled.

I ran across a more reasonable explanation on a couple of sites that pointed to faulty relays on the analog video board, which makes much more sense. My guess is the relays are sticking for some reason until the machine is powered all the way off, causing them to reset.

Does anyone know from experience if in fact the relays are to blame? I would very much like to repair this thing myself if I can locate the faulty parts and order suitable replacements. I'm experienced in soldering and doing work on circuitry, so this isn't a problem. But I don't really want to take this thing all the way apart without being reasonably sure I am looking in the right place.

Any and all technical information (the more technical and detailed the better) is appreciated.

 

[CTho9305]

First, this isn't highly technical. Second, clear the CMOS. I'm not sure exactly how you do that, but it solves all sorts of funky problems with those ugly, slow and expensive computers . I remember a couple years ago we had a LOT of problems with them not turning on/off, and clearing the CMOS solved them.

edit: Ignore the not highly technical part then .

 

[diehlr]

Originally posted by: CTho9305
First, this isn't highly technical. Second, clear the CMOS. I'm not sure exactly how you do that, but it solves all sorts of funky problems with those ugly, slow and expensive computers . I remember a couple years ago we had a LOT of problems with them not turning on/off, and clearing the CMOS solved them.

I've tried clearing anything and everything multiple times. I am 100% sure simply "clearing" something is not the solution. And second, if it doesn't sound technical, let me be a little more specific as to what I meant by technical in my original post- I would like any and all circuit-level schematics of the board in question, and if anyone knows the part number of the relays in question, that would be very helpful.

 

[lexxmac]

I'm a mac tech, but It has been a while since I worked on a Rev A iMac. I seem to remeber that replacing the analog board fixed the problem, but I'll have to check. I may have the schematics in question, but like I said I'll have to check on that.

EDIT
-Oh, about the flyback transformer, if you do open your iMac up, be very careful of it, that's one of the 'danger' parts on the CRT

 

[diehlr]

Originally posted by: lexxmac
I'm a mac tech, but It has been a while since I worked on a Rev A iMac. I seem to remeber that replacing the analog board fixed the problem, but I'll have to check. I may have the schematics in question, but like I said I'll have to check on that.

Thanks! I'm hoping I will be able to repair the existing analog board, but if worse comes to worse, I may have to just replace it. Hopefully not .

 

[AbsolutDealage]

Originally posted by: lexxmac
I'm a mac tech

Wow, I didn't know there was such a thing

 

[glugglug]

You can reset the PRAM (cmos) by holding down command-option-P-R when you turn the thing on or reboot. There is also a program called TechTool that will do a more complete job of it. lots of settings you would expect to be in prefs files not in battery memory, like mouse speed, some color preferences, disk cache size, menu blink options, & folder view settings will be lost when you do this, in addition to the obvious things like the system clock and SCSI ID of the boot volume if applicable..

 

[diehlr]

Originally posted by: glugglug
You can reset the PRAM (cmos) by holding down command-option-P-R when you turn the thing on or reboot. There is also a program called TechTool that will do a more complete job of it. lots of settings you would expect to be in prefs files not in battery memory, like mouse speed, some color preferences, disk cache size, menu blink options, & folder view settings will be lost when you do this, in addition to the obvious things like the system clock and SCSI ID of the boot volume if applicable..

Thanks for the advice, but I have already tried resetting the PRAM, CUDA, and everything else on the machine. The problem I am having is a hardware level failure and isn't something that can be fixed by a firmware reset.