I would like some insights about iMac's power supplies, especially the Early 2009 24" (A1225 EMC 2267).

I decided to tinker with an old broken iMac (machine that shuts itself down) to make it a Media Center with my Rasberry Pi and its Hifiberry + an LCD controller. But to do it right, I need to use the power supply for the screen (+ fan and why not also power the raspi).

But for that, I need two things:

The voltages (and current) of the output connectors which are obviously not standard (12 pins for the 12v-3.3v and 12 pins for the 24v that runs towards the inverter of the screen, although for the latter, I don't really care).

Know which pins to connect to activate the power supply (if I had this element, I could measure the voltages myself).

For now, I've spotted three things:

* Pin 1 = Ground

* Pin 2 = 12v always on

* Pin 4 = 3.3v always on

* Pin 6 = Ground

For the rest, I'm drying up, if you'd give me a hand, I'd be extremely grateful.

Hello,

I've made some progress in my tests, I've managed to activate the power supply!

It is sufficient to make a bridge between the ground (PIN 1,6,7,12) and the 3.3V (PIN 4), which activates pins 8, 9, 10

So we end up with these values:

On the 12V output (2x6 pins)

• Pin 1 = GND
• Pin 2 = 12VDC -> Always On
• Pin 3 = GND -> if SATA connected
• Pin 4 = 3.3VDC -> Always On -> PS_ON
• Pin 5 =?
• Pin 6 = GND
• Pin 7 = GND
• Pin 8 = 12VDC -> If On
• Pin 9 = 12VDC -> If On
• Pin 10 = 12VDC -> If On
• Pin 11 =?
• Pin 12 = GND

On the 24v output (1x12 pins)

• Pin 1 = 24VDC -> Always On
• Pin 2 = 24VDC -> Always On
• Pin 3 = 24VDC -> Always On
• Pin 4 = 24VDC -> Always On
• Pin 5 = 24VDC -> Always On
• Pin 6 = GND
• Pin 7 = GND
• Pin 8 = GND
• Pin 9 = GND
• Pin 10 = GND
• Pin 11 =?
• Pin 12 =?

A last connector is present on the power supply, it is a ground that seems to be dedicated to the 5V (it is connected to one of the SATA GNDs and to the motherboard).

We can see that this power supply only provides 12V and 24V, as surprising as it may seem, it is the motherboard that is in charge of transforming the 12V into 5V! (the cable between the power supply, the motherboard and the hard disk confirms it).

So I still have Pin 5 and 11 on the 12V port and Pin 11 and 12 on the 24V port which are a mystery (if someone has an idea, I'm a buyer)...

I found the electrical schematic of a Liteon PE324101UN-LF power supply (which also seems to be used in other iMacs), there seems to be some info, but I can only guess the usefulness of these pins....

On the 12V output (2x6 pins)

• Pin 1 >>- +12V
• Pin 2 >>- +12V
• Pin 3 >>- +12V
• Pin 4 >>- GND
• Pin 5 >>- GND
• Pin 6 >>- GND
• Pin 7 >>- +5VS
• Pin 8 >>- +5VS
• Pin 9 >>- +5VS
• Pin 10 <<<- AC_DET (Alternating Current Detection?)
• Pin 11 <<<- P_DIM (Power DIMming?)
• Pin 12 <<<- BL (LCD BackLight?)
• Pin 12 <<<- PS_ON (PowerSupply ON !)

On both 24v outputs (1x12 pins)

• Pin 1 >>- 24V
• Pin 2 >>- 24V
• Pin 3 >>- 24V
• Pin 4 >>- 24V
• Pin 5 >>- 24V
• Pin 6 >>- GND
• Pin 7 >>- GND
• Pin 8 >>- GND
• Pin 9 >>- GND
• Pin 10 >>- GND
• Pin 11 <<<- P_DIM (Power DIMMING?)
• Pin 12 <<<- BL_ON (BackLight ON?)

For AC_DET, I found this definition:

AC adapter voltage detection input. Valid AC adapter input range is set using resistors forming a voltage divider which are connected between ACDET & GND and ACDET & AC adapter.

P_DIM should reduce the output power of the 24V PINs to reduce the brightness of the display?

BL_ON, turn on the LCD?

In short, full of new questions.

Well, I finally succeeded in measuring everything I wanted.

I made a little schematic for those who would be interested.

If there's a mistake, don't hesitate to tell me.

oldturkey03> BL_ON needs to be powered in 5v to turn on the screen. For P_Dim, it's more complicated, I think it's about frequency, but the LCD converter will do it.

mayer>My power supply works very well, it is here a question of knowing what its specifications are to power a Raspberry Pi and other accessories without Apple motherboard! ;)

⟐ Answered December 15, 2024 at 10:17 MST

I have everything you need (or so I think) to use my imac lcd panel (panel LM240WU2 ( SL) ( B4 ) ) as a monitor for other pc

http://i62.tinypic.com/112e876.jpg

http://i61.tinypic.com/2mwxct2.jpg

also I connect the cable from the inverter to the lcd

this http://i59.tinypic.com/f10dts.jpg to http://i57.tinypic.com/f2itxd.jpg

Connect the power cord from the iMac ( white ) energy to the panel. and I connect the power adapter to the board vga 12V 2A

but does not work , connect via a PC to give vga video signal and does not work

do I wrong ?

Help please :(

⟐ Answered April 02, 2026 at 23:00 MST

⟐ Answer accepted January 16, 2010 at 2:51 MST

can i change my Graphic Card to ATI RADEON HD 4850 GDDR3?

⟐ Commented April 08, 2020 at 12:54 MST

I own a early 2009 Intel 24" Alu iMac 2.66ghz. I was using it the other day and suddenly it went dead. I tried turning it back on - nothing happened. So I changed the power cord and tried it in another room - nothing.

So I found the guide on here and swapped the power supply with a new unit. It didn't fix the problem :(

I was thinking it might be the logic board but surely it would do something if it was this? I get nothing, no fans,noise, nothing.

Any other suggestions on what I could check? Oh, and I did try the SMU reset and reseating the RAM...

PS. I've no applecare.

Many thanks!!

Martin

⟐ Answered February 25, 2019 at 20:16 MST

10.6.6

I'm having problems almost every time I attempt a Software update or other software download and update. I've replaced the hard drive, zeroed the drive, reformatted, installed Stuffit 14. TechTool Pro runs clear, 50 pass RAM check, Disk Utility runs clear, Norton Anti-Virus is clear. Yet almost every time I try to download a update I get a decompression error. If I download just one update at a time I can eventually get it to install.

⟐ Answered August 26, 2012 at 11:49 MST

How can I diagnose? I'm unable to boot into diagnostic mode, that appears to be something added in later models.

⟐ Commented December 02, 2018 at 12:50 MST

Apple says:

Three long tones, three short tones, three long tones: EFI ROM corruption is detected, and the computer is in EFI ROM recovery mode.

Newer computers automatically recover from a corrupted ROM; when this occurs, a progress bar appears on the screen during ROM recovery mode. Don't disturb your Mac while the ROM recovery takes place. When recovery is complete, your Mac restarts.

If you need to restore the EFI ROM on certain Mac computers produced before 2008, you'll need to use a Firmware Restoration CD to restore the EFI ROM. Search Apple Downloads for the right CD image for your computer.

This is a 2009 and I get nothing on the screen. After doing a lot of research I find no definitive answers. Some have suggested changing the battery but I have never seen a battery failure on one of these.

Does anyone have actual experience with this problem? @danj @reecee

UPDATE SOLVED!

After all these years I finally got in a genuine EFI failure (no Hanky Panky)

The battery was fine.

I ordered in a BIOS EFI firmware chip: Apple iMac 24" A1225 Logic board: 820-2491-A

from these guys on eBay

newkcomputernewkcomputer (1745)

http://www.ebay.com/itm/252527384768?_tr...

Put it in and it now works great! I was actually surprised ;-)

I emailed these guys and asked them to join us for some additional expertise.

⟐ Commented April 12, 2017 at 12:29 MST

Hey wizards, here's a nice one:

My early 2009 Imac shuts off unexpectedly all the time. It started a year ago, with maybe one shutdown a week. Then it happened more and more, to the point where it shuts of many times a day. Here's some info:

-It runs on snow leopard. I don't have the original troubleshoot DVD anymore, but I do have the SL DVD.

-It's almost like, the more it turns off, and I put it back on (each day), the less likely it seems to shut off. Almost as if it needs a "warmup" or something, of me switching it on each time. But eventually it shuts of all the same.

-It completely shuts off, and I hear a little "tick" when the screen turns black.

-It also seems to shut down when apps ( even normal ones like internet browsers ) are being used. I NEED to photoshop for my work, but guess how that's working out at the moment.

-All LED lights inside the mac check out, nothing wrong there.

-The fans don't go crazy or anything like that. The Mac doesn't seem to heat up more than it usually does..

Hardware I've already replaced to deal with this problem:

-Harddrive ( new one, and newly formatted with Snow Lion )

-Powersupply ( new one )

-RAM ( new ones )

I don't have the dough to buy a new Mac, and I've already invested in new hardware. I'm at the point where I can cry, because it's making me hopeless. I want to fix it but I don't have any hope left that it can be fixed...

I need your wisdom...

.

⟐ Commented February 06, 2016 at 9:18 MST

I've been looking around to see if I can swap out my current graphics card for a better one. Having seen many conflicting and sometimes confusing answers I thought I'd ask on here in the hope someone has tried and tested!

I have an early 2009 24 inch iMac Intel Core 2 Duo 3.06ghz with 8gb RAM and the GPU is an ATI Radeon Mobility HD 4850

I saw a guide on here that showed someone successfully changing theirs, but what I wanted to know was if it was possible to upgrade to a different card with more memory, 1GB or higher.

Things that worry me are, would another card fit ok? would there be overheating issues? and is there Apple firmware that needs to be pre installed for it to work?

Many thanks in advance

⟐ Commented March 19, 2025 at 4:13 MST

I have a 3-year old iMac 24-inch aluminum and some time ago, while i was Skyping with my girlfriend, he just shut down like the power cable was pulled out of it.

After this I turned on my iMac again and it kept shutting down without any warning.

Have been searching the internet many times about how to fix this and this is what I've done by now:

- Booting in OS X from external HDD (verifying if it was HD related)

- Removed the internal HD and booted from the external one

- Replaced RAM with brand new ones

- SMC reset, PRAM reset, VRAM..

- Several Apple Hardware Tests, short and extended for several hours (no problems found). Note that the iMac NEVER shut down while performing these tests.

- Full clean install on the internal HDD itself

- Performed Repair Disk and Disk Permissions

- Created new user, logged in with that account (no luck either)

- Checked the Power Cord for any damage AND switched to other wall sockets

- Installed smcFanControl and turned the fans to full speed so it got cool enough (still shutting down)

- Installed SystemLoad and performed those tests while monitoring the temperature with TemperatureMonitor.

- Dismantled the iMac (since I'm out of warranty), cleaned out the fans, vent from CPU. Pulled out the PSU to check if something was burned through.

- Checked the diagnostic LED's on the logic board.

> LED #1 is on when iMac is off;

> LED #1, #2, #3, #4 are on when the iMac is on.

All of these things did NOT fix the problem! I'm out of desperate tries and as a university student, i don't have enough money left to buy a new one nor, because I'm out of warranty, fix it due to the high costs.

Hi there! Unfortunately the iMac is still not repaired. I have completely dismantled the iMac and replaced the thermal paste of the CPU and GPU but still no luck.

I notice that the display gets really hot on the top left corner after 5Mins. while the iMac is in stand-by. I don't have to open any programs or what so ever to make it hot after 5mins. .. while the iMac is up and running, all 4 LED lights are on but i get an image, i can just work on the imac without problem until it just turns itself off.

So i don't know which comment to follow, is it a temperature problem or something else? No idea...

⟐ Commented May 18, 2019 at 6:00 MST

With the SSD in an external case the iMac sees it just fine and I was able to install OS 10.11 on it and even boot from it that way.

When I install it in the iMac it won’t boot from it at all. I just get a white screen with no flashing question mark??

⟐ Answered April 12, 2021 at 14:32 MST

⟐ Commented January 26, 2025 at 12:35 MST

I would like to upgrade the NVIDIA GeForce 9400M Graphics Processors with 256MB of DDRS SDRAM of shared memory to:

A Quadro 4000 GPU card with at least 1GB of VRAM.

Is this possible?

⟐ Answered July 16, 2020 at 13:41 MST

This is my first ever post here! I have an early 2009 imac 2.93ghz with nvidia gt120 gfx card.

I'd like to know if it's possible to upgrade this card to a newer card and have my mac still work?

I have read about possible EFI/driver issues and wondered if anyone has any experience of this or can provide me with some info on how to fix them if they occur.

The nvidia gt120 & gt130 has an unaddressed issue that apple has never fixed that causes crashes, so I would like to replace this card, with a new card and it needs to be an upgrade as this card no longer works with anything after Snow Leopard 10.6.3 without crashing.

Many thanks guys,

hardtofin :)

⟐ Commented November 16, 2017 at 21:00 MST

Good morning everybody!

Is it possibile to upgrade my CPU - (socket P) E8335 2,93 Ghz Core 2 Duo on my old Early 2009 24" iMac?

Thanks very much for your support.

Kind regards

Stefano

⟐ Commented July 08, 2022 at 5:03 MST

Strangely you can let it stay in idle the entire night or install an OS or perform a memory check and it will run stable without shut off but after starting anything on the web e.g. a Youtube Video or launch a web site the system will get off within 5 minutes.

I replaced the Delta power supply with a new one from LiteOn, but this hasn't solved my issue. I also have taken a look on the four LEDs on the right side of the logic board. When the sudden power off takes place, three of the four LEDs cease to light up. Only the first LED from left stays on every time. Also I can turn the iMac on again immediately after shut down at every time.

My closest assumption is that the graphics card might have an issue but I think that this kind of error would more likely lead to freezing screen or kernel panics instead of sudden power off.

⟐ Commented February 06, 2023 at 4:12 MST

⟐ Answer accepted August 25, 2018 at 18:27 MST

⟐ Answer edited May 22, 2015 at 8:18 MST

⟐ Answer edited October 09, 2019 at 17:30 MST