Measuring iMac G5 Power Supply Voltages at Connector Plug Pinouts

Exactly how how do you test the PSUs out on the Apple iMacs?
How do you turn on the iMac G5 power supply when it is out of the computer?

Apple iMac G5 PSU With Ambient Light Sensor Shown

iMac G5 Power Supply Connector – P-1

1. +3.3 – BlackA3B 12. +3.3 – BlackA3B
2. +3.3 – BlackA3B 13. +12v – BrownA3B
3. GND – BlackB4B 14. GND – BlackC4B
4. +5v Gray/PurpleA4B 15. On/Off – Gray
5. GND – BlackB4B 16. GND – BlackC4B
6. +5v Gray/PurpleA4B 17. GND – BlackC4B
7. GND – BlackB4B 18. GND – BlackC4B
8. PG – Blue 19. +12v – BrownA3B
9. +5.1Vsb – Purple 20. +5v Gray/PurpleA4B
10. +12v – BrownA3B 21. +5v Gray/PurpleA4B
11. GND 22. +20v to +24v – Brown

On the 661-3350 power supply and other similar PSUs, jumper pins 15 (gray) and 16 (blk/gnd) to turn the PSU on. With the power supply on, you should be able to read all the voltages listed above with a DC voltage meter. Between pins 22 and any GND pin, you will see approx. 24vdc, which is needed for the backlight. Note that the plug is numbered on the wired side of the connector plug. You will need some good lighting to see the numbers. A small flashlight comes in handy.

When reading the voltages, it is always a good idea to check both for proper DC voltage and AC ripple voltage. Note that AC ripple voltage should be relatively low, in the low millivolts range.

From what I have been able to tell, the other power supplies in both the 17 inch and 20 inch iMac G5 computers all used the same DC voltage pinout arrangements. I believe the voltage pinout arrangements are different on the Intel iMacs and some of the iSight models.

Please read the detailed information for repairing Apple iMac G5 power supplies.

Note: (see below) PG acronym represents the Power Good signal and VSB represents Voltage Stand By.

If anyone has more information for any of the power supplies (especially the pinout arrangement) used on the various Mac products, including the various PPC models, Intel Models, and Power Macs, please send it to me.

Thank you.



Voltage pinouts listed above cover the following Apple PSUs: 661-3350, 661-3289, 614-0353, 614-0296, 614-0297, 661-3351 614-0923 614-0352 614-0294, AP14P46, 614-0398, 614-0326, 661-3625, 661-3289, AP13PC97, 614-0279, DPS-180SB, A 614-0334, 614-0366, 614-0326, 614-0398, 614-0353, 614-0328, 661-3627, 614-0327, 614-0325, 614-0365, 614-0329, 661-3290, Manufacturer Part Numbers: DPS-180QB-1A Rev 01, API4PC47, DPS-180QB ) along with a number of different manufacturers including: (ACBel API3PC96 – Celetronix Q45B – NPFC), and additional manufacturers’ part numbers than what is listed here.

PG acronym represents the Power Good signal. I found the following reference in the Wikipedia when it comes to talking about power supplies in general for PCs.

In addition to the voltages and currents that a computer needs to operate, power supplies also provide a signal called the Power-Good signal, sometimes written as Power_OK or Power_Good or you can distinguish it by its gray color. Its purpose is to tell the computer all is well with the power supply and that the computer can continue to operate normally. If the Power-Good signal is not present at startup, the CPU is held in reset state. If a Power-Good signal goes down during operation the CPU will shutdown. The Power-Good signal prevents the computer from attempting to operate on improper voltages and damaging itself.

The ATX specification defines the Power-Good signal as a +5 volt (V) signal generated in the power supply when it has passed its internal self-tests and the outputs have stabilized. This normally takes between 0.1 and 0.5 seconds after the power supply is switched on. The signal is then sent to the motherboard, where it is received by the processor timer chip that controls the reset line to the processor.

iSight G5 Apple Mother Board 820-1766-A

Pictured below are the capacitor locations and values for Apple iMac G5 iSight Mother Board 820-1766-A motherboards.

iSight 1145

For high quality, low ESR, computer and switching power supply grade, long life, high temperature rated, and high current rated capacitors, go to, your source for the Apple in you.

Note that there are at least two different iSight G5 models with different logic cards. Take a look at this one to confirm which model iSight you have.

Click the following link to purchase the iSight Mother Board Capacitors Kit.

Here is a down-loadable procedure for G5 iSight dis-assembly which can take you all the way down to and including the iSight motherboard removal.


Jim Warholic

iMac G5 iSight Intel Core 2 Duo Disassembly

How do you disassemble the Apple iMac G5 iSight Intel Duo Core Mac?

I first removed the memory modules by unscrewing the bottom access panel.

The Plexiglas on the front is held on by a magnetic strip around the lip.

I used a piece of clear tape to grab it and gently pulled it away. A small suction cup works also.

From there you can get to the screws that hold the outside bezel in place.

From there, you can lift off the front bezel (disconnecting the camera cable at the top) and gain access to the display bracket screws on each side.

Once you take those out, then the display will lift out of the chassis. Just keep track of the four sets of cables that plug in the back side of the display and there is one main MOB display connector cable with a clip.

Here is a video that shows a few of those items:

Note there were more connectors on the bottom of the display on the Aluminum iMac G5 that I had an opportunity to work on. I noted which connecters went where before disconnecting them.

Below are pictures of the Apple iMac G5 iSight Intel Core 2 Duo model.

Pictured above is the inside of the iMac G5 Intel Core 2 Duo. Note the power supply in the upper left corner, followed by the hard drive in the upper middle, and the DVD/CD Super Drive on the right side. Located directly below the hard drive is the mother board (main logic card) with the main heatsink screwed directly to the mother board (MOB). To the right and left of the MOB are the fans. To the the right and left side of the fans are the built-in small speakers.

Pictured above are the onboard status lights (LEDs) located on the main logic card. These LEDs can also been seen in the first picture of the Apple iMac G5 Intel with the bezel removed. However, I don’t believe these status lights match up to the older iMac G5 PPC onboard status lights. Citation required.

Here is some additional information on some of the Apple iSight G5 models.

Below is a video of an earlier generation iMac G5 iSight model. I believe this video is of an interim iMac G5 model.



Note the memory is located in the bottom of the iMac. Access is by removing a small screw in the access panel. I also suggest you remove the memory first.

Article by: Jim Warholic

Jim is President of Professional Web Services, Inc., an Internet marketing services company specializing in both the B2B and B2C market place. If you would like to find out more information about getting your business more sales and qualified leads online, contact Professional Web Services today.