Red diode on G5 (2005 2,7 ghz liquid cooled) processor card

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Level 1

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Red diode on G5 (2005 2,7 ghz liquid cooled) processor card

I'm trying to revive a 2005 G5 (2x2,7ghz liquid cooled). The computer powers up but does not go any further. I have noticed a red diode on one of the two processor card. Does anybody knwow what that means ? I've checked the processor assembly, removed both cards, there is no leak, but the red diode lights up on one of the processor card when I power up the computer. Thank you for your help !

Earlier Mac models

Posted on Apr 19, 2024 7:34 AM

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Answer 1

BDAqua

Level 10

239,777 points

Apr 24, 2024 10:35 AM in response to Lionel Rey

Diagnostic LEDs Power Mac G5 (Late 2005) logic boards include a set of LEDs to help service providers troubleshoot the computers. The LEDs are located to the left of the top bank of DIMM slots. Top bank of DIMM slots (Bank 1) Edge of main log

Notes for LED Table

Power Mac G5 (Late 2005 Dual 2.0/2.3 GHz) logic boards include LEDs 1–5 and LED 7, but not LED 6. Power Mac G5 (Late 2005 Quad) logic boards include LEDs 1–7.
CPU A is located closest to the PCI Express slots; CPU B is located below CPU A (closer to the power supply). Make sure CPU screws are tight.
LEDs 3, 4, and 5 operate differently from the other LEDs. They remain off until you remove the air deflector (clear door inside the side access panel), at which point they should go
on. If LED 3, 4, or 5 is on before you remove the air deflector, check the operation of the air deflector sensor. Note that the fans will run at high speed while the air deflector is removed.
LED 5 verifies that Open Firmware has loaded. To allow time for it to load, be sure to wait at least one minute from first power up before you check this LED.
Some logic boards have two additional LEDs: one located near the bottom edge of the logic board and the other to the right of the top bank of DIM

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Answer 2

BDAqua

Level 10

239,777 points

Apr 27, 2024 7:35 AM in response to Lionel Rey

Interesting Red LED story...

PowerMac G5 startup failures, red LED beh… - Apple Community

It's not the heat sheild sensor is it???

https://forums.macrumors.com/threads/old-powermac-g5-red-light-on-logic-board.1841158/

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Answer 3

Lionel Rey Author

Level 1

9 points

Apr 26, 2024 7:23 AM in response to BDAqua

Hi,

Unfortunately the 2.7 Ghz liquid cooled G5 is an early 2005 model and it does not have these leds on the logic board. The red led which prevents the G5 from booting.is on one of the processor card .

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Answer 4

Lionel Rey Author

Level 1

9 points

Apr 28, 2024 4:59 AM in response to BDAqua

At least it seems all is not completely lost since I read from someone else's experience that sometimes the red diode would light up on one or two of the processor cards (and the computer would not boot) and sometimes it would boot as usual when no diode would glow red... Im waiting for my new account on the other discussion board to be authorized and I will post there, hoping someone has the answer to the clue !

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