I re-set my PMU (dual 2.0 G5 Powermac) but still have issues.

Question

Level 4

1,488 points

I re-set my PMU (dual 2.0 G5 Powermac) but still have issues.

The symptoms are fans that always or often go to high when its not hot, and then the mac shuts down or becomes unresponsive. When i got it ( fixing for a friend) it would power on but not boot up and the screen remained dark - often with the indicator light blinking. Pressing the PMU seemed to help greatly, but symptoms have crept back.... Any pointers or ideas appreciated.

Grant

Posted on Aug 22, 2012 9:33 AM

Reply

Answer 1

Best reply

BDAqua

Level 10

239,213 points

Aug 23, 2012 9:57 AM in response to Grant Lenahan

Hi Grant, seems several problems...

The thermal paste on the CPUs likely needs replacing after this length of time...

Can you count the beeps or flashes?

1 beep = no RAM installed

2 beeps = incompatible RAM types

3 beeps = no good banks

4 beeps = no good boot images in the boot ROM (and/or bad sys config block)

5 beeps = processor is not usable

In addition to the beeps, on some computers the power LED will flash a corresponding number of times plus one. The LED will repeat the sequence after approximately a 5-second pause. The tones are only played once.

Note: In this case, a flash is considered to be 1/4 second or 250 ms or greater in length.

If you're sure the RAM is good, try the Hair Dryer trick...

http://discussions.apple.com/message.jspa?messageID=13240047#13240047

https://discussions.apple.com/thread/3061091?answerId=15223603022#15223603022#15223603

https://discussions.apple.com/thread/2620983?answerId=15499912022#15499912022#15499912

https://discussions.apple.com/thread/3175959?answerId=15613068022#15613068022#15613068

https://discussions.apple.com/thread/3270112

https://discussions.apple.com/thread/3287993?answerId=16053892022#16053892022#16053892

No power light at all...

https://discussions.apple.com/thread/3692775?tstart=0

It can show on any G5, and even many other computers & electronic devices of the period.

http://www.macintouch.com/reliability/pmg5.html

http://lowendmac.com/ppc/power-macintosh-g5.html

And see this last one in particular...

https://discussions.apple.com/thread/3507385?answerId=16781690022#16781690022

Heat gun better...

https://discussions.apple.com/thread/3916312?tstart=0

Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...

See which one your G5 has...

http://eshop.macsales.com/item/Newer%20Technology/CR2032/

http://eshop.macsales.com/item/Newer%20Technology/BAA36VPRAM/

Reply

Answer 2

Grant Lenahan Author

Level 4

1,488 points

Aug 23, 2012 10:16 AM in response to Grant Lenahan

First, thank you very much for the lengthy and helpful reply. I'm leaving for the sirport shortly, so digging through it will take some time.

I can narrow a few things down. The RAM should be fine. Once i reset the PMU, the G5 boots properly and works. The fans even went to idle. And then, they started to roar and it shut off.

So its not a RAM-like syptom. I have heard about the thermal grease bit. I have tons of the stuff - any complexity removing the modulesnad the processors? I see some screws back there.

When i get back I will:

1. count beeps

2. read you many links

Thanks, again

Grant

Reply

Answer 3

Grant Lenahan Author

Level 4

1,488 points

Aug 27, 2012 9:09 AM in response to BDAqua

I am still interested in how to get the CPU modules out to re-seat and greae the chips to the heatsink.

On another note, i did soem more testing.

Upon turn on it frequently mits a number of beeps, does not boot, and the small white led on the front panel blinks. Upon power-off and re-start it boots normally (3/3 times).

Twice i counted the beeps:

1. 9 beeps (mostly sure)

2. 7 beeps (positive)

Anything that can be gleened from this?

Grant

Reply

Answer 4

BDAqua

Level 10

239,213 points

Aug 27, 2012 10:30 AM in response to Grant Lenahan

I am still interested in how to get the CPU modules out to re-seat and greae the chips to the heatsink.

I was hoping for japamac or one of the other experts to drop in with the best advice on this, let's wait & see on that point. 🙂

Might be time to replace the PRAM Battery, 4 years is close to their lifespan, far less if ever without AC power, & can cause strange startup problems...

See which one your G5 has...

http://eshop.macsales.com/item/Newer%20Technology/CR2032/

http://eshop.macsales.com/item/Newer%20Technology/BAA36VPRAM/

Reply

Answer 5

Grant Lenahan Author

Level 4

1,488 points

Aug 27, 2012 10:41 AM in response to BDAqua

I plan to replace the battery, but i must re-emphasize - i'm ntyo concerned with start up problems. I'm concerned with heat control issues - the unit cranks up the fans and ultimately goes wild and shuts down even when it is not even remotely hot. This is a known problem, its the solution part that's vague.

As to the battery - i will replace it if the machine is not toast. However, it measure 3.68V. There could be high internal reistance to be sure, but its not dead. Typically dead oens measure down around 3V no load. So i dont suspect that is the root cause, although it could influence the abilkity to re-learn adn store parameters.

Does anyone know what 7 and 9 beeps mean?

Does anyone knwo how to re-calibrate the temperature control / power control unit? I understand there's a non-existant program that Apple has.....etc.

Thanks again,

Grant

Reply