Mac g5 dual 2GHZ processors will not power on

Can you open the DVD drive to insert a disk (see hint below)? If so, insert the original system disk, power down, then press the power button and hold the (alt/Option key) down until you see a blue screen. Any valid OS X volumes should show up in the center...

The original system disk should contain the Apple Hardware Toolkit (AHT), run the long version of the utility (could take a couple of hours-depending on the amount of memory installed). Either way it should tell you if your motherboard, or any hardware is bad or not working.

Hint: If you hold the (right) mouse button down while your machine is starting up, the CD/DVD drive door should kick open and let you place or remove a disk...helpful when you have a bad or uninitialized disk stuck in the tray.

Best Regards.

thanks for the reply ultralites,

the system was not booting up at all, I removed the video card and now it starts up, I can hear the mac chime, and a few seconds later it shuts back down. In other words, The computer will not boot at all with the video card in its slot, I thought this might indicate a bad video card but it doesn't explain why the system shuts down immediately after?

OK. If you have another Mac available, you should be able to connect to it's hard drive by booting it into target disk mode.

Connect them both with a firewire cable, then Hold the T button down (on the bad one) while starting up, continue to hold the T button down until the drive is powered and shows up on your (good mac's) desktop as an external firewire.

If that works, you should be able to run disk utility against it and try to determine what is wrong with the startup.

The thing is, I don't have another mac... I've pulled everything out of the system and used only one CPU on the top but it is still the same problem, It will boot without the video card but will not stay on fro more than a few seconds.

What was the reason for taking out the 2nd processor?

To elimate a possible problem with one of the CPU's or memory. This computer has a brand new power supply.

If it is a dual processor G5, than I would replace both processors, in about 10yrs servicing macs, I have never seen a processor go bad, only logic boards (motherboard). Probably a good idea to remove everything but one memory module for each processor and make sure each module is in the same slot as the other (i.e. top top), that way you have matched memory pairs.

Based on the lights that you are seeing, it does sound like a logic board or memory issue, but if so you should be able to place your video card into another slot and have it work.

I would put both processors back in, place only two memory modules into it, and leave the video card out.  Hold the alt/option key down while pressing the power button, keep holding the alt key down and see if it stays powered on.

I'm going to need to pick up a mac keyboard from somewhere. I put the RAM in matching slots on top and bottom, they weren't before, but now I don't hear the mac "chime" noise. One thing I just noticed is that when I turn it on, sometimes it will turn off immediately, other times it will last longer. The red led on the motherboard will stay lit the entire time its on. Right as it's powering down by itself you will hear the same clicking noise you hear when it powers up, and the white led above the power switch will flash. The power  LED on the front of the computer does not stay on when pressed.

ok. I will check back with this thread tomorrow.
Just FYI here is a link with detailed instructions/diagrams on matching memory for G5s
http://docs.info.apple.com/article.html?artnum=86414

i would try re seating the processors or taking one out and then try taking out the other one to see if it will load... if it does not detect the processor it wont boot is the reason for this. i know for a fact macs are picky about memory so if you didnt get the correct type it will not boot (i put in wrong memory once and it did the exact same thing) http://eshop.macsales.com/shop/memory/ usually can tell you what memory you will need for the G5...

also the red light on the motherboard is suppose to be on its means its on essentially...

you said u put in a new power supply... macs usually have different pin out for the power so if it was not a mac power supply that could be the issue...

the thing that is throwing me off when you take out the video card it trys to start what makes me think its a bad video card but it should still boot...

next up is the firewire target disk mode... PC's will see it as a external drive (must have software installed to be able to surf threw the drive though)

i would also try pressing the reset button inside the computer to reset all pram (i think its by the battary on the motherboard)

let me know if this helps but what i have heard if this happens re seating (take out and put back in) of the processor usually fixes it but since you have done that already it seems it might be the logic board...

Ya, i've tried to re-seat both processors, memory, etc multiple times. Everything that is in the system is compatible. It just stopped working one day. It appears to be a bad logic board.

were you able to get a mac keyboard?

make sure u hit that reset button inside the mac on the logic board (essentially zaps the pram with out having to hold down a silly key combo)

crashelite: i tried to hold down the button, i think it's labled "PMU"

Does anyone know where I can find a logic board other than a mac service center? I've tried typing in what I beleive to be the part number but I cannot find anything. The service centers are telling me $700 for this board.

http://www.welovemacs.com/g5lowprp66.html


"Pricing: $740.95 to purchase a new board outright or $580.95 for board exchange price. Your old board/CPU must be sent back to WLM and received before a new board/CPU can be ordered and shipped.

Since different revisons exist for many models, either your computer's serial number or the serial number printed on your logic board itself are required before we can fill advanced exchange or outright purchase orders for logic boards. Both serials are preferred. (Unless you already know the part you need.)

The G5 serial number is located inside the access panel, directly below the air deflector. The logic board serial number is printed next to the DIMM sockets. "


i was thinking this one more then others on their site cause you said you thought it might also be your CPU :)

too bad ifixit.com does not do G5 towers

btw the apple service manual says you must do a thermal calibration after putting in the new board
"
Thermal Calibration
To ensure proper fan and temperature control in the Power Mac G5, you must run Apple
Service Diagnostic whenever you replace a processor or logic board with a new processor
or logic board. You must also run the diagnostic if you re-install the same processor but in
a different connector from the one in which it was originally installed. Apple Service
Diagnostic for Power Mac G5 is available as a download from the Disc Images section of
the Apple Service Source website.
Note: The calibration process of Apple Service Diagnostic requires a controlled
environment to ensure accurate ambient temperature readings. Computers under test
must have the transparent air deector installed and the door sensor switch must be
operable. Units under test should also be located away from heating and air conditioning
ventilation systems and the fan exhaust of other machines. Ambient temperature should
not go above 77 degrees Fahrenheit or 25 degrees Centigrade.
" - apple G5 service guide

also the LED diagnostic codes
"
RAM and Processor Veri
cation: Power-On Self Test
A power-on self test in the computers ROM automatically runs whenever the computer is
started up after being fully shut down (the test does not run if the computer is only
restarted). If the test detects a problem, the status LED located above the power button on
the front of the computer will ash in the following ways:
" 2 Flashes: No RAM is installed or detected.
" 3 Flashes: Incompatible RAM types are installed.
" 4 Flashes: No RAM banks passed memory testing.
" 5 Flashes: No good boot images are detected in the boot ROM (and/or there is a bad
sys config block).
" 6 Flashes: The processor is not usable.
"

and finally the apple flow for essentially the issue that you are having

No boot tone (LED on, fans spin, no boot tone, video) or
No video (LED on, fans spin, boot tone, no video)
1. Reseat video card
2. Replace video card
3. Replace front panel board cable
4. Replace speaker
5. Replace front panel board
6. Replace logic board

Ya, it isn't worth replacing the logic board in this old mac.

ebay for parts :) video cards usually sell for quite a bit on ebay

I usually use ebay for all my laptop parts. I just can't find the motherboard i need on ebay. There's a white label on the disk that says 630-4834...

Do you guys think this could be the logic board? The computer without the video card will turn on, mac chime will sound, LED on optical drive will light up, all fans will be spinning, system appears to be booting, a few seconds later the system shuts down. Sometimes it shuts down after one minute other times right after the chime sometimes before the chime. Any help would be greatly appreciated. Thanks. By the way I do not have a mac keyboard.

I noticed that when i try booting with the case open...I experience the red led being on and fan sound very loudm no boot chime..But when i closed and locked the case , i heard the boot chime... Just thought i leave some info.

Finally someone has some useful information.