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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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iMac Intel 27" EMC 2429 Power Supply voltage values?

Where can I find the pin diagram with voltage values so that I may test the power supply? thank you

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Is PIN 1 the bottom left?

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Hello Aaron, thank you for the response, my iMac will not power on, I am looking for some guide that can point out the voltages for each pin the power supply, that way I can use my multi-meter and check if the power supply is the problem or not.

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7 Answers

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Here’s the info on the pinouts: Won't power up and only 1 diagnostic LED

Give @oldturkey03 an upvote if it helps.

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Thank you Dan, much appreciated!

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Pin 1 Ground

Pin 3 5V power for Hard Drive(s). Note: If present, the 12V power will come directly from the Power Supply to the Hard Drive thru the power harness cable.

Pin 4 Standby 12V power (permanent power coming from power supply and present as long as AC cable is connected, even if computer is off); corresponds to LED #1

Pin 6 Backlight Control pulse width modulated signal (from logic board to LED backlight board, to adjust the backlight level setting according to user setup)

Pin 11 12V Run-Mode power to logic board (coming from power supply, present as long as system is on or asleep); corresponds to LED #2

Pin12 Power On Request signal (from logic board to power supply when power button is pressed)

Pin 13 Backlight Enable (signal from logic board to Backlight Controller board, to enable backlight

"Press power button and Verify if system turns ON. You may alternately check for presence of a 12V DC signal between pin 11 and pin 1 of logic board when power button is pressed."

Update (10/02/2018)

Just connect the power supply and then measure it on the logic board side. That way you know that the logic board gets all the voltages from the power supply. Use the image from the answer on here Won't power up and only 1 diagnostic LED

You can also trace the wire from the connector to the logic board to detrmine the pins on the power supply, by using the same image

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@oldturkey03

Thanks for that info. I have one of the many 27” iMacs with blown GPUs, and I’m converting it into a monitor with a cheap driver board off eBay. But I want to use the original PSU and inverter, not the cheap one (which, based on reviews, doesn’t drive the backlight with original brightness).

I have a pinout that's probably right, but I'm not sure what some of these abbreviations mean:

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http://hqlaptoprepair.co.uk/imac-a1312-p...

Can you give me a description of the non-obvious ones? Thanks!

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I'm also converting a 27" mid 2011 imac into a monitor and was wondering what did you end up doing? Because I would love to reuse the original psu and the inverter to achieve maximum brightness.

Pleaselet me know

Kind regards

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Any luck with this? Want to do the same with the original PSU and inverter!

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Me too! Have a controller board for the lcd but would love to use the original inverter and psu!!

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I'm also in the middle of this. I don't know what you mean by "except the obvious". But I think that the SMB ones, (pint 10, 2 and 3) 5V connector for the Hard drive and optical driver. Let's keep us posted on this project !

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I am also trying to use the APPLE Backlight Inverter Bd instead of the CHINA Backlight Inverter bd to solve the BRIGHTNESS issue.

on PWM signal, I just used 3v DCin (I ordered a PWM generator to supply 13kHz, 3V)

not sure why I am only getting 12.51 Vout when using the APPLE Backlight inverter bd.

LCD - NO BACKLIGHT

3.) iMac with Apple Inverter, no PSU and no LogicBoard

INVERTER VOLTAGES

Vout 12.51V (CN2.1)

Vin 12.58v (CN1.2)

ENA 3.22v (CN1.1)

PWM 3.02v (CN1.3)

LCD - BRIGHTNESS LOW (iMac as MONITOR using China Inverter/Driver/Controller)

CA-255 China Inverter board

2.) iMac with China inverter, no PSU and no LogicBoard

INVERTER VOLTAGES

Vout 32.5v (CN4.1)

Vout 87.6v (CN4.1) with LCD disconnected

Vin 11.93v (CN1.1)

ENA 4.64v (CN1.3)

PWM 0v (CN1.4)

LCD -BRIGHTNESS EXCELLENT (Normal 2011 iMac EMC2429)

1). iMac with Apple inverter, PSU and LogicBoard (normal 2011 iMac EMC2429)

INVERTER VOLTAGES

Vout 36.5v (CN2.1)

Vin 11.8v (CN1.2)

ENA 3.22v (CN1.1)

PWM 3.08v (CN1.3)

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PSU

Pin 16 GND >> SATA pin 10,11,12 GND_12V

Pin 15 VIN 12V >> INV pin 2 if ON

Pin 14 12V >> MB pin 12 if ON

Pin 13 VIN 12V >> INV pin 5 if ON

Pin 12 12V >> SATA pin 13,14,15 12V if ON

Pin 11 12V >> MB pin 11 if ON

Pin 10 3,3V >> MB pin 13 thin cable if ON

Pin 9 GND? >> MB pin 5

Pin 1 GND? >> MB pin 14

Pin 2 GND_12V >> INV pin 6

Pin 3 >> MB pin 10 half dun 4v when OFF

Pin 4 GND_12V >> INV pin 4

Pin 5 12V >> MB pin 4 always ON

Pin 6 GND? >> MB pin 7

Pin 7 3,3V >> MB pin 2 thin cable if ON

Pin 8 GND >> MB pin 1

Connect pin 3

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to pin 2 to power up pin 11, 12,13,14,15

Seems like the photo from oldturkey03 is completely wrong….. correct?

INVERTER

Pin 1 ENA / BL_ON

Pin 2 VIN

Pin 3 PWM

Pin 4 GND

Pin 5 VIN

Pin 6 GND

Seems that pin 1 needs 5V to turn the Blacklight ON.

Has some of you already got it to work with the original inverter? And with or without the original power supply (PSU)?

Please share diagram etc. Thanks!!

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Pinout from oldturkey03 doesn’t seems right to me.

I have done some investigation myself, see picture.

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Would like to hear if i’m correct?

Anyone already got it working with the original inverter?

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Hi, is 3.3V on if mb plugged in and pc turned on? From psu only i 'm getting oscillating voltage on pins 7, 10 from 1.2-2.4v. Trying to rule out power supply. Any help appreciated

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I am also trying to use the APPLE Backlight Inverter Bd instead of the CHINA Backlight Inverter bd to solve the BRIGHTNESS issue.

still working on it.

on PWM signal, I just used 3v DCin (I ordered a PWM generator to supply 13kHz, 3V, but not received yet.

not sure why I am only getting 12.51 Vout when using the APPLE Backlight inverter bd.

Here are Voltage measurement I took.

Be CAREFUL - DANGER HIGH VOLTAGE.

LCD - NO BACKLIGHT

3.) iMac with Apple Inverter, no PSU and no LogicBoard

INVERTER VOLTAGES

Vout 12.51V (CN2.1)

Vin 12.58v (CN1.2)

ENA 3.22v (CN1.1)

PWM 3.02v (CN1.3)

————————————————————————————————————————————————————

LCD - BRIGHTNESS LOW (iMac as MONITOR using China Inverter/Driver/Controller)

CA-255 China Inverter board

2.) iMac with China inverter, no PSU and no LogicBoard

INVERTER VOLTAGES

Vout 32.5v (CN4.1)

Vout 87.6v (CN4.1) with LCD disconnected

Vin 11.93v (CN1.1)

ENA 4.64v (CN1.3)

PWM 0v (CN1.4)

————————————————————————————————————————————————————-

LCD -BRIGHTNESS EXCELLENT (Normal 2011 iMac EMC2429)

1). iMac with Apple inverter, PSU and LogicBoard (normal 2011 iMac EMC2429)

INVERTER VOLTAGES

Vout 36.5v (CN2.1)

Vin 11.8v (CN1.2)

ENA 3.22v (CN1.1)

PWM 3.08v (CN1.3)

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