My wifes 2008 iMac 24" just died... :-(

[Lucianrider]

So her late 2008 aluminum iMac went into a reboot loop on its own...
Pulled the plug and pressed the power button, waited 15 secs and plugged it back in.
It half chimes and the screen sometimes flashes gray before becoming totally dead. Black screen etc.

When it tries to boot you can hear the superdrive but that's all. As I said it does not even fully chimes, just a half chime before getting cut off.

I swapped out the ram for some known working ram and same thing. Removed the ram and it beeps.

Tried Target Drive mode and nothing at all. The drive does not show up on my iMac and the screen remains black.

So I am thinking maybe power supply. However I live in St. Lucia, West Indies and there is no repair place here that deals with Macs. I have been into it once about a year ago to change the hard drive which was an upgrade so I am not scared to go into it again.

Is it possible to use a standard PC powersupply in order to check if the Logic Board is good?? I don't mind buying a powersupply and have it shipped to me but I would like to know for sure if this comp can be repaired at a reasonable cost first. Otherwise it will be time to get one of the new iMacs...

Any other suggestions???

 

[AppleNewton]

best bet is to find the powersupply that suits that mac model.
Regular PC PSUs will not work.

 

[tom vilsack]

-when you pulled the power cord how long did you then hold the power button down for? (should be at least 5 secs) then release,replug back on and try powering on...

-have you tryed a pram reset? command/option p-r listen for two chimes/release

-can you boot into open firmware? command option o-f (if you can then try this...)
reset-nvram
set-defaults
reset-all

 

[Brian Y]

Seen this problem before quite a few times. It will be one of:

- Power supply
- Graphics card
- Power *button*

The most likely cause IMO is the power button. A sticky power button will cause it to power off midway through the chime.

 

[Lucianrider]

-when you pulled the power cord how long did you then hold the power button down for? (should be at least 5 secs) then release,replug back on and try powering on...

-have you tryed a pram reset? command/option p-r listen for two chimes/release

-can you boot into open firmware? command option o-f (if you can then try this...)
reset-nvram
set-defaults
reset-all

Yes I held power button down for at least 5 secs. I also tried the pram reset but it does not respond at all.

I haven't tried open firmware, not aware that I could. However I don't give much hope for that as it seems to die before even getting close to that point...

But thanks for the comments!

----------

Seen this problem before quite a few times. It will be one of:

- Power supply
- Graphics card
- Power *button*

The most likely cause IMO is the power button. A sticky power button will cause it to power off midway through the chime.

Well that is interesting! How would I go about confirming that??
Can I give it a shot of WD40 or is the stickiness within the switch itself??

 

[Lucianrider]

Well I pulled the iMac apart today and extracted the power supply as it does not appear to be the power switch. Looking carefully at the back of the board I found a surface mounted component that has overheated and discoloured the surrounding board. The solder has also melted and solidified out of shape where it is soldered onto the board.

Here are some pictures showing what I mean.

The highlighted area is where a component looks to have been badly overheated.

A close up of the component.

Identifying label.

Component side of the PSU.

I've been looking for ways to test the PSU without any luck, does anyone know which terminals turn it on and what voltages should be between the various terminals??
Also I can't identify the component, does anyone have that info?

Everything else on the board looks OK including all of the caps...

I've found a number of companies selling the power supply but before I order one I was hoping to get confirmation that its definitely defective...

 

[Lucianrider]

I guess I might as well close the loop on this thread.

I received the powersupply from DV Warehouse and installed it tonight.

Success!!! She booted right up and works perfectly.

My wife is ecstatic as am I!

Whilst it was open, I blew out the dust, removed the cpu fan and cleaned off all the solidified dust. In this case I actually washed the fan out with water which worked a treat. Made sure that I kept the water away from the motor itself.

So the thread can be closed.