Power Mac 5G booting problem any test or solution idea ?

[VLuc]

Dear all,

I'm a french Apple user (so, sorry for my poor English ; I used to be not so bat but I didn't practice for a long time !) and I was given a few days ago an old late 2005 Dual core 2,3 Ghz Power Mac. After a long and meticulous deap cleaning, I cloned an old X.4.11 G5 iMac hard disk and installed it in the Power Mac. (I would have prefered a clean install, but I miss the Tiger CDs and archives…)

The good news is that it worked at he first time ! I only had a clock message and thought the battery was dead, so, bougt a new one. I checked a few things about GPU, RAM and so on ; all fans working, temperatures seems to be OK (even if GPU is a little bit hotter than CPU) and my so precious Nikonscan was running. No uncommun noise, no red light on the card after booting, I was really, really happy !

Then, I shot it down, unplugged it, put the new battery, reset the mother card and (tryed to) restart…

It didn't.

No "bong", black screen and after a little minute, the fans started to blow really hard. I had to force shooting off by a long stat button pressing.

I tried and retried around 15 times the past few days. Sometimes, it stats without any problem. Sometimes, not. I don't understand…

It seams to be easyer to start after a more or less long period unplugged (maybe it is hasard ?). But after what I call now a "lucky boot", I never managed to restart successfully (no bong, black screen, fans blowing hard after a minute… Forced to hard shhoting off…).

In fact, I don't really know what I can check. I have found the Service Manual of this exact version of the Mac and know 2 or 3 things about recurent watercooling and power supply problems on older versions, but I need some help to investigate more (2,3 dual core doesn't seems to be the more problematic one, isn't it ?). I also think thermal past after 15 years is out. But I didn't find how to change it fo the moment and I'm not sure that it is the biggest problem for the moment. But maybe I'm wrong.

I'd really like to undestrand why sometimes it works without any problem and sometimes, not because this Mac could really, really help me…

Do you have any idea, experience or advice for me ? Of course, I can (try to) answer any question if you need more infos…

Thank you,

Vincent

 

[1042686]

Hi, first thought I’d check your ram & slots. Make sure the ddr1 is installed correctly. Here’s a link.

http://manuals.ramjet.com/powermacg5.pdf

If that is not it, I found this Apple PMG5 work flow you can use to trouble shoot. I used it on my DP2ghz but much of the process is similar & I’ve used it as a logical step by step for my DC2.0ghz as well. See below


[[ Power Mac G5 (June 2004): Power-on LED illuminates when pressed in, but goes out when button is released, fans spin, and there is no boot tone or video

• Verify that the processors are properly seated.
• Verify that the processors’ mounting screws are properly tightened.
• Remove the processors and check for damage to the logic board under the processors. If you see damage, replace the logic board.
• Remove lower processor. If the computer starts up correctly, go to step 5. Otherwise, go to step 6.
• Replace lower processor.
• Replace upper processor.
• Check for trickle voltage on the power supply connector. Refer to “Power Supply Verification” in this chapter. If verification fails, replace power supply.
• Replace logic board.

Power-on LED illuminates when power button is pressed and fans spin continuously but there is no boot tone or video

1. Reseat video card. (Make sure video card is fully inserted in connector and end of card is secured by the connector latch.)
2. Verify speaker cable is fully seated.
3. Reset logic board. Refer to “Resetting the PMU on the Logic Board” in this chapter.
4. Reseat the processor
5. Replace the processor
6. Replace logic board

Resetting the PMU on the Logic Board

The PMU (Power Management Unit) is a microcontroller chip that controls all power functions for this computer. The PMU is a computer within a computer. Its function is to:

1. tell the computer to turn on, turn off, sleep, wake, idle, etc.
2. manage system resets from various commands.
3. maintain parameter RAM (PRAM).
4. manage the real-time clock.

Important: Be very careful when handling the logic board. The PMU is very sensitive and touching the circuitry on the logic board can cause the PMU to crash. If the PMU crashes and is not reset, the battery life goes from about five years to about two days.

Note: For the location of the PMU reset button, see “Logic Board Diagram” in the Views chapter.

Many system problems can be resolved by resetting the PMU chip. When you have a computer that fails to power up, follow this procedure before replacing any modules:

Disconnect the power cord and check the battery in the battery holder. The battery should read 3.3 to 3.7 volts. If the battery is bad, replace it, wait ten seconds, and then proceed to step 2. If the battery is good, go directly to step 2.

Press the PMU reset button once and then proceed to step 3. Do not press the PMU reset button a second time because it could crash the PMU chip.

Wait ten seconds before connecting the power cord and powering on the computer. If the computer does not power on, there is something else wrong with it; refer to the “Startup Failures” section of “Symptom Charts” in this chapter.

Note: The above procedure resets the computer’s PRAM. After resetting the PMU, be sure to reset the time, date, and other system parameter settings.

If you want to check the power supply, then this might come in handy:

Power Supply Verification

To power on, the computer’s logic board requires a “trickle” power of +5V. If the system fails to power on, first reset the PMU. Then follow the procedure outlined below to determine whether the problem is related to the power supply.

Note: To verify the power supply, you need a volt meter.

• Remove the power cord from the computer.
• Open the computer, lay it on its side with the access side facing up.
• Remove the front inlet fan assembly.
• Remove the black plastic cap covering the 24-pin power supply cable connector (the P1 or largest connector). The cap fits tightly over the connector. To remove it, rock the cap gently forward and backward as you lift up.

Note: This is a top view of the connector when it is plugged into the logic board.

• Press the release latch on the connector and disconnect the cable from the logic board.

• Plug a known good power cord into the computer. Do not turn on the computer.
• On the power supply cable connector: connect the black lead of the volt meter to pin 23 and connect the red lead of the volt meter to pin 1.

Note: This is a bottom view of the connector when it is unplugged and facing up.

The volt meter should measure approximately +5V. If you do not get a reading of +5V, recheck the volt meter connections and measure the voltage again. If the voltage is still not present, replace the power supply.

Pinouts

Power Supply P1 Connector

For now you do not want to replace anything but just check to see if you can narrow it down.]]

Sorry it’s not in French (your English is better than my French LOL! ) & best of luck to you.

 

[VLuc]

Thank you very much Ryan ! I take the idea.

I re-checked RAM, GPU, and reset again PMU. The Mac has been unplugged yesturday, I tried to start once and… it worked. So I'm checking and picturing all what I can regarding the ability to run a few tasks, check temperature, fa control, smell and so on when it is possible ! But I'm a little bit afraid about restarting…

I really don't understand why a "cold start" seems to be OK and why the "hot start" ou "restart" fails ecah time, even if the Mac was only used 2 or 3 minutes before. Don't even have an idea if it could be software or hardware problem…

Don't even know if the machine is safe. So I unplugg it as it's not in use…

Or maybe is it just a lazy Mac. Booting only once a day…

 

[1042686]

Well, These boxes are old & their components get old & cranky. There are noted issues with the ram slot traces on the logic board failing - usually if the pmg5 is cold, you can’t get the PM started but by blowing a hot hair dryer on the ram slots for a couple minutes, this heats up the traces, expands the trace alloys, & allows the machine to boot up. Unfortunately the only real fix for this problem is a new logic board & certainly this is a worst case scenario. There are many other things to check first & are more likely to be causing the pmg5 failure. This seems to be the opposite of what you’re experiencing too which I agree is really weird.

It could be a failing power supply with your intermittent boot but then why the black screen & ramping fans? I’ve had two psu failures in pmg5 machines & neither did this - it either worked or didn’t. I’m not saying it’s not this, but it’s a weird symptom from what I’ve experienced. Over heating psu maybe? Is that a thing lol?

Without going through all the paces, I’d guess it’s a loose or improperly seated CPU/heatsink, possibly mismatched/incorrectly installed ram sticks, or heat related - maybe failure due to old worn out thermal paste. These boxes run hot so you could repaste & then reseat the cpu, ensure it’s on correctly - something that should be done either way. Check the ram using the guide above while you’re at it.

Anyhow, the no-boot/bong, black screen & ramped up fans points me to check these things alongside pmu/lobo reset etc. I hope you figure it out!

best of luck to you.

 

[VLuc]

Thank you very much RhianB for your kind and argued answer. And for your interrest in this "old lady Mac" ;-)

I think I'll (re) start from scratch. Put every card, RAM, fan, connector out and double check everything I install back ; check the list you gave me and… put my finger crossed !

Thank you again !