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White 24" imac 2.16 dead...sometimes

C

chairman3281

macrumors newbie
Original poster
Apr 6, 2013
9
0
North Carolina
Late 2006 24" 2.16

*Suddenly went dead, 18 months ago

*Apple Service and separate Apple Repair shop said bad power supply, but maybe bad logic board. No way to tell without replacing power supply first.

*Bought new 27". Let 24" sit.

*Took it apart today. First diagnostic light (power) is green. Computer dead. No activity.

*When inverter cable is disconnected from Logic Board, Computer powers up, start-up chime sounds, and I assume that if the LCD worked everything would be ok. All 4 diagnostic lights are green.

*Reconnect the inverter cable, goes dead

Any help from you experienced and knowledgable Apple users will be greatly appreciated.
 
LCD inverter do take up a bit of power, so going by that logic there is a good chance that the power supply is not dead per se, but can't give enough power for the whole system.

Edit: try to leave the inverter plugged in, but unplug everything you can; hard-drive, superdrive, etc... just to see if you can boot with the screen on. Because maybe the inverter's gone bad, it can happen.
 
Thank you for responding Francois. I disconnected everything I could find...hard drive, dvd, one fan, one speaker. No change. Still dead with inverter connected, seems ok without. There was a slight difference though. Before disconnecting these things, I could turn the computer on with the switch, but it would not turn the unit off. I had to unplug it. With these things unplugged, the power switch functioned normally. Does this sound like it still could be the power supply? If so, can I check the output with a multimeter, that I am only semi-competent with?

Edit: There is one other thing that may be relevant thinking about a weak power supply. When the inverter is connected and the power switch is pressed, the third diagnostic light flickers, very quickly and very weakly. And the fan under the left speaker jumps, but doesn't start. If you can think of anything that would help let me know. Thanks again for your help.
 
Last edited:
chairman3281 said:
Thank you for responding Francois. I disconnected everything I could find...hard drive, dvd, one fan, one speaker. No change. Still dead with inverter connected, seems ok without. There was a slight difference though. Before disconnecting these things, I could turn the computer on with the switch, but it would not turn the unit off. I had to unplug it. With these things unplugged, the power switch functioned normally. Does this sound like it still could be the power supply? If so, can I check the output with a multimeter, that I am only semi-competent with?
Click to expand...

You can only test the voltage this way but not the load, example:

Lets say the output on one channel is 5 Volts 10 Amps, you then have to connect a load which is 5 Volts and needs 10 Amps, only then you can see if it can deliver that amount and if the power Supply will switch off.
There are probably a few Voltages and you need to put a load on all of them, so most likely 12-5-3 Volts and multiple channels.
This is not for the faint hearted and you need "professional" gear to do this.
 
Thanks. Yeah, I'm afraid you are a little over my head there. Can you think of anything else I can check short of buying a power supply? I guess I can do that and then, if it doesn't solve the problem, try to sell it on e-bay.
 
chairman3281 said:
Thanks. Yeah, I'm afraid you are a little over my head there. Can you think of anything else I can check short of buying a power supply? I guess I can do that and then, if it doesn't solve the problem, try to sell it on e-bay.
Click to expand...

What about this, use the new 27" Mac in Target display mode, start the old one up with a Cable connected to the new iMac and start it up, does it show anything on the new iMac?

You know, it could be both or either the power supply or the inverter.
 
Does the old 2006 iMac have a motherboard battery?

Years ago (not sure if it's still the case), one of the symptoms of a dead motherboard battery is a computer that wouldn't respond when the power-on button was pressed. Press the button and....nothing.

Replace the battery and.... back to normal.
 
Like you said earlier, you should get a new power supply, and even if it's not that you can still sell it as is and make a small profit off it.
 
justperry said:
What about this, use the new 27" Mac in Target display mode, start the old one up with a Cable connected to the new iMac and start it up, does it show anything on the new iMac?

You know, it could be both or either the power supply or the inverter.
Click to expand...

Thank you. That's a great idea. I was not familiar with Target display mode, so I read up on it a bit. Am I right that I need a cable to connect the two computers from the Mini Display Port on the 24 to the Mini Display Port on the 27? I went to the Apple Store today and a "Specialist" sold me a Thunderbolt cable and said the two were the same and this one would work. If they are, I can't get them to work.

I'm beginning to think that you are right about the weak PS. I understand that there have been some problems with the capacitors on this PS and MOB. The power supply looks brand new. No swollen caps or leakage any where. There is some sticky residue on the bottom of the logic board under a group of capacitors near the connection for the inverter. Would leaking caps cause this type of problem or would that just kill the motherboard?

I am still going to try to find the correct cable tomorrow, but I am beginning to think the weak PS idea may be it.

Thanks, again for your help. If you think of anything else, please let me know.

----------
FrancoisC said:
Like you said earlier, you should get a new power supply, and even if it's not that you can still sell it as is and make a small profit off it.
Click to expand...

I think you're right. This may be the best way. What do you think the chances are that it is the logic board?
 
chairman3281 said:
Thank you. That's a great idea. I was not familiar with Target display mode, so I read up on it a bit. Am I right that I need a cable to connect the two computers from the Mini Display Port on the 24 to the Mini Display Port on the 27? I went to the Apple Store today and a "Specialist" sold me a Thunderbolt cable and said the two were the same and this one would work. If they are, I can't get them to work.

I'm beginning to think that you are right about the weak PS. I understand that there have been some problems with the capacitors on this PS and MOB. The power supply looks brand new. No swollen caps or leakage any where. There is some sticky residue on the bottom of the logic board under a group of capacitors near the connection for the inverter. Would leaking caps cause this type of problem or would that just kill the motherboard?

I am still going to try to find the correct cable tomorrow, but I am beginning to think the weak PS idea may be it.

Thanks, again for your help. If you think of anything else, please let me know.

----------



I think you're right. This may be the best way. What do you think the chances are that it is the logic board?
Click to expand...

The sticky stuff is almost sure to be hot glue to secure the Caps, most of the time it is yellowish.

I do not know what cable you need, I know TDM can be used but how I do not know, you can probably find out on Apple's site, I think Thunderbolt can't be used since the older Mac does not have one.
Display Port seems to be the right choice but again I am not sure.
 
justperry said:
The sticky stuff is almost sure to be hot glue to secure the Caps, most of the time it is yellowish.

I do not know what cable you need, I know TDM can be used but how I do not know, you can probably find out on Apple's site, I think Thunderbolt can't be used since the older Mac does not have one.
Display Port seems to be the right choice but again I am not sure.
Click to expand...

My 27" is pre-Thunderbolt also. The 24" hasn't been used in 18 months so I guess I can take a little time and research it some more before I start yanking out parts and buying new ones. Thanks for your help. I'll let you know what I finally discover.
 
macthefork said:
Did you check or replace the PRAM battery on the logic board as suggested by fisherrman? That can cause these symptoms, as mentioned in this previous post. If you Google this, there's many posts that discuss this.
Click to expand...

This has nothing to do with a dead PRAM battery, or the Power Supply has gone bad, or the inverter/screen takes too much current and the Power Supply shuts down for safety, like an electronic fuse.
 
The PRAM or CMOS battery controls the Extensible Firmware Interface (EFI) during boot. If the battery is weak or dead, some components on the Logic Board may not be initialized such as the SATA controllers, memory controllers, then the video controllers, etc. It also can control some power components. It's after the EFI has completed that the computer can contiune the boot from the OS on the drive.

The OP's problem may well not be the PRAM/CMOS Battery. But, since it easy to check and replace, it's usually the first thing I check and replace on a computer this old that is having boot problems. These batteries only last five years or so. Much less if the computer is not plugged in for a period of time.
 
justperry said:
Here's an Apple page I just found.

OS X Lion: Use another Mac as a display
Click to expand...

Thanks, Perry. That site was very informative. The Thunderbolt cable I bought at the Apple Store fits the Mini Display Port on the 27" but the 24", despite documentation, doesn't have a MDP but a Mini DVI Port. Any combination of cables and adapters I have been able to find is too expensive to make that feasible. I appreciate your help. If you think of anything else, please let me know.
 
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