I bought an HP Quadro FX 4500 and flashed it for use on the G5 per instructions on the macforums. The flash didn't work, it resulted in a black screen on the G5. I put in the old video card and heard a chime but no video. I tried to reset the board by pressing the switch same response . I removed the battery and reinstalled and same . I left it overnight with the plug off and connected it this morning and now I get no chime . I removed the video card and powered it up but the same issue. There are 2 red lights on. #2 and #7 . 2 I think means cpu overheat (not sure how since I didn’t touch anything there) and 7 is cpu halt. Just in case someone asks, yes the pcie cable which provides extra power to the video card was installed . I am not sure what happened. I can’t get my beloved G5 working again . Any ideas ?? I attached a photo of the red lights .
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Beloved Quad G5 black screen and no chime.. Please help!
- Thread starter Melchieor
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A bit of an update today. I left the G5 unplugged and PRAM battery out for the night . This morning I pressed the reset button and put the battery back in and turned it on. I heard a chime but black screen and same 2 LED lights on. 
I dont know. Maybe pure bad luck. If you feel for it, remove the cover and check if the pumps are working. Your G5 can boot with 1 cpu in ( the one of top, bottom cpu is ‘slave’). What I would do is pram reset, try booting, then reseat all stick of ram, try booting, then the fun part, remove your lcs, change thermal paste and install the top cpu, reinstall, try booting, if this work, install second cpu.
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I would be cautious with the smc reset on the logic board. Its written in the service manual that If you press this switch multiple time in a row, theres a risk of corrupting the smc. If you press this switch, press once for 10sec.
Thanks for your reply. Yesterday I tried a few things, removing the PRAM battery and pressing the reset button , and once again leaving it overnight unplugged . This morning I plugged it all in and put the PRAM battery but took the graphics card out. I am hearing a chime but then the 2 lights come back on. I tried removing the LCS however I couldn't find a tutorial for this specific model (quad 2.5) and was not able to remove it. I am starting to lose hope.
The lcs for a quad is easy to remove. First remove the T bracket on top to make way and check down there. Theres a aluminium plate and all the hex screw are there to be remove.
in order:
-remove the G5 name plate
-remove the front fan/front duck/ and rear fan
-remove the T bracket on top of the lcs
-remove the 4 short hex screw securing the power lead for the processor x2 (black plastic bracket on the rear with wire)
-remove the 8 long hex screw securing the mounting plate (big aluminium plate) (8 screw or 10 I dont remember)
-Rock gently and lift the assembly (dont forget to remove the lcs power cable.
* theres also long taper screw/post, they are there to guide the assembly when you reinstall the whole shebang.
Good luck. It can be hard the first time when you dont want to break stuff.
These G5's are old systems. Messing with the graphics card may have probably knocked something or banged against something whilst inserting and then removing the graphics card.
The G5 quad service manual can be found here https://www.scribd.com/doc/21536787...60149026&source=hp_affiliate&medium=affiliate
The G5 quad service manual can be found here https://www.scribd.com/doc/21536787...60149026&source=hp_affiliate&medium=affiliate
. So after buying several liquid cooling systems and another quad I am having the exact same issue . The overheat led and the halt led . I think that there is just no power getting to the liquid cooler . Is there any way to test this ?