Power a iMac G5 iSight(A1145) with a ATX power supply?

Dear everyone, I am from China, just got a cheap iMac G5 logic board from a dead 20" model(A1145), I am trying my best to get it work again, I have modified 2 heat sinks to get them fit the original heat tube place. now the biggest problem how to power the board with a ATX PSU, I have googled for some while but with no luck, all I can find is how to power a first generation G5 with a ATX(http://jimwarholic.com/category/imac_g5), but the iSight model uses a different PSU, only 5 wires are out from the PSU, the 5 wires go into the inverter board, then 14 wires to the logic board.

The pinout of the 14-wire connector is:

Group 1:
















I presume the LCD_PWM is used to adjust the brightness of the LCD back light, but what are the "INV_CPU_HI" and "SYS_POWERUP_L_BUF" pins for?

any help will be greatly appreciated! :)

Answer this question I have this problem too

Is this a good question?

Score 1


Thanks for your reply Markus:) The problem is I don't have the DC-DC board, all I have is the logic board, now the diagnose LED 1 and 2 are on, and the white power LED can be turned on after the power button pressed, and I can feel some heat from the CPU and GPU, but after about 8 seconds, it automatically turned off... it seems there is no POST, I've got a USB flash disk, when normally it's plugged into the USB port, it flashes its LED a few times, indicated that it has been configured by the USB host and the LED then goes to constant on, but when I plug it to the G5 board, the LED flashes all the time, I presume either the USB host on the board is broken, or not being powered on, or it is being kept at Reset state by the POST process(don't know how mac do the POST process)? or I didn't get the board powered properly? can anybody give me some tip where the problem might be? I REALLY REALLY want to have a PowerPC machine as my working platform. Thank you in advance and for my poor English...

by Eric

Hi, I have a 20" imac need to replace the power supply too, did you fix this finially? Thanks

by Spawn

Add a comment

4 Answers

Most Helpful Answer

why did you bother about the 14 pins ? - if you still have the 5 pin connector you only need to worry about the 5 pins ;-)

i've found the pinout on insanelymac:

Grey: +12V

Grey: +12V

Black: ground

Black: ground

Brown: PFW (battery powered signal between +3 and +6.5 volt to switch power supply on)

Was this answer helpful?

Score 3


+ research

by mayer

Add a comment

Thanks Markus, that is the old model, the PSU directly connected to the logic board, in the iSight model, there is a DC-DC board between the PSU board and the logic board, and the P1 connector is only 14pins. Anyway still thanks for your post :) cheers

- Eric

Was this answer helpful?

Score 0


sorry if it was the wrong one. i should have looked inside my "butchered" imac

by markus weiher

Add a comment


I guess SYS_POWERUP_L_BUF may be the ATX PS_ON !

Did you find more clue ?

I have an Intel iMac LogicBoard and i would like to bring it back to life too !


Was this answer helpful?

Score 0
Add a comment

In fact on my iMac Intel 17" logicboard there's only have 12 pins.

I guess 20" needs INV_CPU_HI and LCD_PWM but 17" doesn't.

PP12V_ALL ALL for "always" on.

PP12V_RUN RUN for when PSU is on.

But PP12V_ALL and PP3V3_ALL can't be provided by an ATX PSU (there is only the PP5V_ALL)


12V | GND

12V | 12V


GND | 5V

3.3V | 3.3V

doesn't work !

Was this answer helpful?

Score 0
Add a comment

Add your answer

Eric will be eternally grateful.

View Statistics:

Past 24 Hours: 0

Past 7 Days: 6

Past 30 Days: 33

All Time: 7,472