Unusual PPC PM 2.7 GHz G5 Startup Problem

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Level 3

565 points

Unusual PPC PM 2.7 GHz G5 Startup Problem

I downloaded the Service Manual for the G5 Macs, and in the troubleshooting section under the "no-startup" section, the only symptoms shown are ones where the chime is absent. My G5 always boots when cold (say 1 hour or more since last boot), and will run properly all day. There are no errors or error messages when the computer is running. But if run for a while (say 10 - 15 minutes or longer), it will not restart, or boot from a shutdown again, until it is off for an hour or more. The thing is, *the chime is always present* on any attempt at restart or re-boot. Then there is either a black screen, a grey screen with no Apple, or a grey screen with an Apple but no spinning gear. New 3.6V lithium battery, PMU reset, PRAM reset with no improvement.

To me this seems like a thermal problem... either a bad sensor or bad circuitry interfacing with a sensor. I have read of an "Ambient Board," a "Media Bay Sensor," and an "Air Deflector Sensor." These all seem to be very small PC boards with on-board thermal sensors plus circuitry. I removed and cleaned the "Ambient Board" because it was easy to access. The other two are really buried, so I haven't touched them.

I have "Hardware Monitor" by Marcel Bresink, and it reports all temperatures quite far below the "target" values after considerable running time. So it seems the problem is not an actual high temperature, but maybe a mis-read of one or more sensors.

I have eliminated software as a cause (I think) by re-formatting my HD and re-installing the original Mac OS X Tiger from the Apple Install Disc #1... same problem. The combo update to 10.4.11 didn't help, either. Running the "Apple Hardware Test" from Apple Install Disc #1 results in all "passes."

What does it mean if the chime is working? How about if the chime works and the Apple logo appears. but no spinning gear? Any comments?

PowerMac Dual 2.7 GHz G5, Mac OS X (10.4.11), May 2005 Build

Posted on Sep 9, 2009 10:32 PM

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Answer 1

japamac

Level 7

24,400 points

Sep 10, 2009 2:06 AM in response to Bill Strohm

Hi-

Check the troubleshooting techniques for a gray screen on boot:
http://support.apple.com/kb/TS2570

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Answer 2

Sep 10, 2009 2:07 AM in response to Bill Strohm

If the thing is failing because it senses temperatures are too high it will record it in the error logs. Anything useful in those?

Are there any external peripherals attached? Have you tried it with just the mouse?

Have you tried a new hard drive or tried booting from an external hard drive? My gut tells me this is your problem.

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Answer 3

Bill Strohm Author

Level 3

565 points

Sep 10, 2009 10:12 AM in response to japamac

Thanks, japamac, I read that article, but the problem is that it assumes a consistent gray screen whenever startup is attempted. As I wrote above, this is not the case. The symptoms are random... sometimes a gray screen, sometimes the Apple logo comes up, but no spinning gear, and when cold, everything works fine. I don't think the article addresses this particular issue.

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Answer 4

Bill Strohm Author

Level 3

565 points

Sep 10, 2009 10:20 AM in response to DaddyPaycheck

Daddypaycheck,

What "Error Logs" do you mean? The Console says nothing regarding errors. Terminal just gives me the introductory command line. Where do I look for an error log?

Only peripherals are Kensington TurboMouse, Apple extended keyboard, speakers (off), my Ethernet connection to my MacSense MIH-120 NAT router, and a USB connection to an Epson SC740 printer (off). And once again, the failures to boot are related to "time on" of the computer itself. The router is always on.

Message was edited by: Bill Strohm

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Answer 5

The hatter

Level 9

61,031 points

Sep 10, 2009 10:21 AM in response to Bill Strohm

System Profile -> Logs and from there system.log and panic.log

Do you get audio output from applications? so it isn't just audio?

How about booting into Open Firmware and the reset-nvram from there? Always a good base point to rule out hardware problems.

There were two liquid coolant units with the 2.7DP. Everything A-okay on that front? the fact temps are well within or below norm would seem to suggest so.

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Answer 6

Bill Strohm Author

Level 3

565 points

Sep 10, 2009 12:22 PM in response to The hatter

Wow... had never scrolled down that far in System Profile before. In the System Log... what does this mean? "ApplicationServices.framework/Frameworks/ATS.framework/Support/ATSServer: (-3230) Cannot use ATS Persistent Store - switching to old FODB cache code"

Got this after waiting about an hour and then booting in "Safe" mode. That was the last entry in the System Log. But the system booted up just fine.

There is no problem with video or audio once system boots. Once again, does anyone know what IS working when the chime occurs but no video signal makes it to the monitor (black screen)? What IS working when the chime + gray screen come up but no Apple logo appears? What IS working when chime + gray screen + Apple logo all work, but no spinning gear appears?

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Answer 7

The hatter

Level 9

61,031 points

Sep 10, 2009 12:33 PM in response to Bill Strohm

Early boot is handled by Open Firmware. Why I suggested booting into OF and reset nvram. Easier than zap pram, too.

OF should supply even basic video output.

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Answer 8

Bill Strohm Author

Level 3

565 points

Sep 10, 2009 1:03 PM in response to The hatter

If my computer won't boot, how can it "boot into Open Firmware?" And what the heck is "Open Firmware?" And how does booting into that (if my computer will do that) help solve my problem? Or is it just a "workaround?"

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Answer 9

The hatter

Level 9

61,031 points

Sep 10, 2009 2:11 PM in response to Bill Strohm

Try it.

Hold down 4 keys on startup:

command option o f

OF is the BIOS to PowerMacs going back to post-NuBus. The ROM firmware or BIOS/OF is the pre-boot process, the boot-loader.

http://osxbook.com/book/bonus/ancient/whatismacosx//arch_boot.html

http://www.netneurotic.de/mac/openfirmware.html

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Answer 10

Sep 10, 2009 4:18 PM in response to Bill Strohm

Have you tried booting with the plastic door off? I had a similar problem - boot when cold, no boot when warm. With the door off, the computer would boot every time. After the login screen appeared I would put the doors back.

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Answer 11

Bill Strohm Author

Level 3

565 points

Sep 10, 2009 5:42 PM in response to The hatter

Tried command-option-o-f after shutdown the last time I had been up & running. Got a black screen; one of the common failure modes. So apparently the Mac cannot get to the "Open Firmware" point when it fails to boot.

"Have you tried booting with the plastic door off? I had a similar problem - boot when cold, no boot when warm. With the door off, the computer would boot every time. After the login screen appeared I would put the doors back." - No, I have never tried that. Apple says the computer will not run properly with the plastic air deflector missing, although they might just mean it will not cool properly. The Service Manual mentions an "air deflector sensor label" that must be in place on the plastic air deflector. My computer has never had anyone else open it except me, but I will check for the presence of that label. Supposedly if the label is missing, the fans may run at high speed, but my Mac does not have that symptom.

What about the "Thermal Calibration" that the manual says is required if a processor is replaced or the processors are switched in their sockets? Never done on this Mac, but is it possible I need to have the Apple people do a thermal calibration? Would a drifted calibration cause this kind of problem? There is a disc image available to them which supports that calibration, but I cannot access it. I would need a "Service Provider" user ID and password to download it from Apple.

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Answer 12

Sep 12, 2009 5:52 AM in response to Bill Strohm

There is no label on the air deflector for my 2.5 power mac. But one of the tabs is colored white for sensor detection. For the short period of time it takes for the computer to boot, leaving off the air deflector should cause no harm.

Thermal calibration is not possible unless the CPU configuration has changed. This option will be "greyed out" and not selectable.

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Answer 13

Bill Strohm Author

Level 3

565 points

Sep 12, 2009 3:11 PM in response to Paul Kopetka

The white color you mention is in fact the "label" called out in the manual. Silver on on side, white on the other. Mine does have that.

OK, I will try first restarting with the air deflector in place, and then immediately with it out, when boot up fails.

I am surprised that the option to thermally calibrate a computer is not available at all times to the service people, whether the CPU has been moved/replaced or not. I would think that after long use, the calibration could drift and need to be re-done. If nothing else, it would verify that the various thermal sensors are still operating. Seems dumb to grey out that option.

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Answer 14

Bill Strohm Author

Level 3

565 points

Sep 13, 2009 11:13 AM in response to Paul Kopetka

I did several things today:

1) Fired up computer (cold, of course) with metal side panel off but plastic air deflector in place. All six fans turn on properly, and computer boots up fully.

2) After running a while, shut down, removed air deflector panel, and re-booted. The computer booted normally, except that (as Apple wrote in the manual) all fans went to "fast" mode. I let it run a while and opened "Hardware Monitor." That app reported that all fans were at the slow end of their rpm range, i.e. 300 rpm for all fans except the "radiator pump," which read 1250 rpm for both CPUs. So either "Hardware Monitor" is lying to me, or else the monitor points that sends the app information to the app are lying to it. I really do not need this extra complication!

3) I reinstalled the air deflector panel and the metal side panel and attempted to re-boot. The startup process reached the point of showing the Apple logo, but no spinning gear appeared. The fans started out slow, but leaving power on under this condition they gradually sped up until they were running full speed. Then I shut down with the power button, waited about an hour, and now I'm back "on the air."

What does this all mean? Paul Kopetka, did you ever resolve the cause of this problem?

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Answer 15

Sep 14, 2009 9:51 AM in response to Bill Strohm

The boot problem for my machine was a high temperature alarm on CPU A (from Apple service diagnostics).

Basically, I removed the CPU's and took apart the two heat sinks. Cleaned the copper cooling fins (they were gunked-up), replaced the o-ring seals, flushed the LCS with water, added fresh coolant and applied new thermal grease. The o-rings had taken a set the the seals had begun to weep - no visible liquid but what looked like coolant residue around the heat sink plate.

The fix was surprisingly easy and now the system runs like it was new. Pics are available.

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