G5 won't boot. White LED lights when power button is pushed, click heard.

Question

Unlike some other non-booting G5 stories, mine never makes it past this stage. It's a dual 1.8ghz G5 powermac.
The white LED above the power button turns on when the power button is pressed, a click is heard, but it does not go any further. The LED does not flash at all... no grey screen, no hard-drive access, nada.
When I push the power button with the aluminum side removed (but with the transparent insert in place), I can see the fans twitch like they are going to start spinning, but then immediately stop.
I've tried resetting the PMU, replacing the PRAM(CMOS) battery, another identical type of video card, blowing out the dust with compressed air, removing and swapping memory, but always get this same result.
There was some renovation done in the house recently, but the machine was gently wrapped and moved away from the work. However after 2 weeks of sitting there, it now won't start.
Any help is appreciated. If the 'clicking' of the power supply is being heard (also clicks when I plug in the power cord), does that mean the power supply is likely working? In which case, is it likely a logic board issue?
One thing I noticed upon closer inspection, after removing the main fan, is that the higher processor seems darker than the lower one. Is there a way to remove one processor to test for hardware failure?

Answer 1

Hi subculture,
A power supply is not to difficult to replace. The lower processor must be removed. It is much easier to lay the Mac on its side. A used power supply can be found on ebay. There are 2 main power connector that connect to the logic board. Those can be tested with a DC voltage meter against a pinout chart for your particular model and can be found on google.
Powermac G5 2004 Model
Power Supply P1 Connector
Pin# Signal Color ------ Pin# Signal Color
1 +5Vstb Purple --------- 13 GND Black
2 GND Black ------------- 14 Power ON Green
3 FANtach White/Yellow -- 15 GND Black
4 GND Black ------------- 16 Reserved
5 Reserved -------------- 17 GND Black
6 GND Black ------------- 18 RTNaud(GND) Black
7 +12Vaud (12V2) Yellow - 19 GND Black
8 GND Black ------------- 20 +5V sense Red
9 +3.3V sense Orange ---- 21 GND Black
10 GND Black ------------ 22 -12V Blue
11 GND Black ------------ 23 GND Black
12 Reserved ------------- 24 Reserved
Power Supply P2 Connector
Pin# Signal Color ------- Pin# Signal Color
1 +3.3V Orange ----------- 9 +5V Red
2 +3.3V Orange ---------- 10 +5V Red
3 +3.3V Orange ---------- 11 +5V Red
4 +3.3V Orange ---------- 12 +12V3 Yellow
5 Reserve --------------- 13 +12V3 Yellow
6 +12Vfan Yellow -------- 14 +12V1 Yellow
7 +12Vfan(12V2) Yellow -- 15 +12V1 Yellow
8 +25V White ------------ 16 RTNfan(GND) Black
Power Supply P3 Connector
Pin# Signal Color ------- Pin# Signal Color
1 +5V Red ---------------- 5 +5V Red
2 GND Black -------------- 6 GND Black
3 GND Black -------------- 7 GND Black
4 12V2 Yellow ------------ 8 +12V2 Yellow
Regards