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#368 - 08/06/09 02:56 PM Power Supply Puzzler
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Caution: You need to pour yourself a coffee before you start in on this.

ryck

I have an older 17" iMacG5 with:

1.6 GHz PowerPC Processor
1 MB RAM
533 MHz frontside bus
256 MB PC3200 (400 MHz) SDRAM
80 GB Hard Drive

I few weeks ago I moved it temporarily from one location to another. When I returned it to the first location and plugged it into the power source, I got a bit of a flash.

The power source is an Isobar surge suppressor ( about 12 years old) that has three isolated filter banks (50dB, 75 dB, 100 dB). The machine was plugged into the same 100 dB source that it's always been in.

Within a few days the cursor would freeze and the machine would have to be shut down by holding the power button. On restart The front panel power light would come on but not the monitor. If you listened closely the hard drive could be heard. After about 30 seconds the fans came on high.

I did an SMU reset and everything went back to normal but, after a couple of days, the cursor froze and all of the above had to be repeated. Eventually, the machine would not progress past the condition of: front power light, no monitor, hard drive in motion, fans after about 30 seconds.

It went into the shop who determined the power supply was gone but that everything else, including the logic board, was okay. A new supply was installed and I decided to start from scratch.


1. OSX 10.5.1 was installed with my Family Pack. The install method selected was “Erase and Install”. The only Option chosen was to install just the Canon printer driver.

2. The computer was set up for connection to Airport. A bit of time was spent surfing the web.

3. A software update was done through the Apple site. Nine Apple programs were updated, including the system to 10.5.7.

4. Apple iWork, Microsoft Office, and Canon IP5000 software were installed.

5. In succession, iWork and Office were updated through the Apple and Microsoft sites.

6. Time was spent on the web. The computer was shutdown using Shutdown including the 60 second countdown.

All of this, which included several restarts, occurred without incident.


The next morning

1. The computer was turned on. The front panel power light came on but the monitor did not. After about 30 seconds the fans came on high.

2. The computer was shutdown by holding the power button.

3. Number 1 above was repeated with the same result, and the computer was shutdown by holding the power button.

4. An SMU Reset was attempted by unplugging the power at source (wall socket).

The computer was turned on. The front panel power light came on but the monitor did not. After about 30 seconds the fans came on high. The computer was shutdown by holding the power button.

5. Number 4 above was tried three times with the same result each time.

6. An SMU Reset was attempted by unplugging the power at the computer.

The computer was turned on. The front panel power light AND the opening chord played. The monitor did not come on and after about 30 seconds the fans came on high. The computer was shutdown by holding the power button.

NOTE: This is the only time the chord played. Further attempts at SMU reset, whether unplugging at source or at the computer, all generated the original result: The front panel power light came on but the monitor did not and, after about 30 seconds, the fans came on high.

The machine went back to the shop where it was determined that the replacement power supply was faulty. It was replaced and the shop kept the machine running for a couple of days shutting it off, turning it one, using the software et cetera.

Today

I went this morning to retrieve the machine. You guessed it, they demonstrated the fix only to have the cursor lock-up. The computer was shutdown by holding the power button, but the restart was the power light, no monitor, hard drive in motion and high speed fans after 30 seconds.

The Technicians are now scratching their heads and will check with one of their other shops.

Any ideas of what else the problem might be, or other things to check?
_________________________
ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS Mojave 10.14.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 1TB LaCie USB-C
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#375 - 08/06/09 03:22 PM Re: Power Supply Puzzler [Re: ryck]
MicroMatTech3 Offline


Registered: 08/04/09
When you attempted to reset the SMU, did you follow all of the steps described in:

http://support.apple.com/kb/HT1767?viewlocale=en_US ?
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MicroMat Inc
Makers of TechTool

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#383 - 08/06/09 04:19 PM Re: Power Supply Puzzler [Re: MicroMatTech3]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: MicroMatTech3
When you attempted to reset the SMU, did you follow all of the steps described in:

http://support.apple.com/kb/HT1767?viewlocale=en_US ?

No. The SMU reset document I had only called for: disconnect ALL cables, wait about a minute and a half, plug power back in and press the power button.

Thanks for this new piece. I just called the shop and they weren't aware of it either. They're going to give it a shot.

ryck
_________________________
ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS Mojave 10.14.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 1TB LaCie USB-C
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#420 - 08/06/09 09:36 PM Re: Power Supply Puzzler [Re: ryck]
MicroMatTech3 Offline


Registered: 08/04/09
You are welcome.

It is sometimes difficult to tell exactly which SMU reset instructions go with which model, but the shop should be able to check. In the cases in which there is an SMU reset button inside the computer, it is vital that the steps be followed exactly, because if the right mistake is made, the computer must go back to Apple. I do not think that applies to your model.

Let us know what happens.
_________________________
MicroMat Inc
Makers of TechTool

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#1426 - 08/18/09 04:48 PM Re: Power Supply Puzzler [Re: MicroMatTech3]
ryck Offline


Registered: 08/04/09
Loc: Okanagan Valley
Originally Posted By: MicroMatTech3
Let us know what happens.

Current status (no power supply pun intended) is that it may be an intermittent on the logic board which is, of course, next to impossible to locate. The shop has been very, very diligent and, even though they've thrown everything at this issue, they haven't yet thrown in the towel.

ryck


Edited by ryck (08/18/09 04:48 PM)
Edit Reason: added info
_________________________
ryck

iMac (Retina 5K, 27", 2017), 3.4 GHz Intel Core i5, 8GB RAM, 2400 MHz DDR4
OS Mojave 10.14.6
Canon MX710 Printer
Epson Perfection V500 Photo Scanner
Time Machine on 1TB LaCie USB-C
Carbon Copy Clone on 500GB OWC Mercury OTG Pro

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#1463 - 08/19/09 05:58 AM Re: Power Supply Puzzler [Re: MicroMatTech3]
Virtual1 Offline


Registered: 08/04/09
Loc: Iowa
Considering the variety of SMU reset instructions for different models, I usually:

1) remove power (unplug or pull battery)
2) wait 10 sec
3) press power button and hold for 10 sec
4) while power button is still held, plug AC cord back in.
5) release power button

That seems to cover them all. Many of the laptops have a set of SMC reset pads also.

Although SMU resets only help in maybe 5% of cases of no power on. But it costs nothing and is quick so may as well try.
_________________________
I work for the Department of Redundancy Department

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#1604 - 08/20/09 03:34 PM Re: Power Supply Puzzler [Re: Virtual1]
ganbustein Offline


Registered: 08/04/09
Apple is now advising that you not reset SMC or PMU unnecessarily. See http://support.apple.com/kb/HT1894.

The article doesn't give any insight about why you shouldn't do this. It's possible it's nothing more than a "Let's have a little less voodoo around here" sentiment.

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#1785 - 08/22/09 08:12 AM Re: Power Supply Puzzler [Re: ganbustein]
Virtual1 Offline


Registered: 08/04/09
Loc: Iowa
Apple is now advising that you not reset SMC or PMU unnecessarily

they have also always had the same attitude with PRAM resets. I've never seen them cite a reason for this. They also say in several places to avoid resetting the pram/PMU/SMU/SMC while it's in the process of resetting. (you'll see them say press it ONCE and not a second time) I have no idea what they're trying to avoid/prevent.


_________________________
I work for the Department of Redundancy Department

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#1845 - 08/22/09 10:14 PM Re: Power Supply Puzzler [Re: Virtual1]
ganbustein Offline


Registered: 08/04/09
Ah, now that I have seen an explanation for. They're trying to avoid hanging the PMU. (The PMU is a computer. It can crash, too.)

I think maybe their reasoning is that, each time you reset the PMU, there is a slight risk that it won't recover properly from the reset. The symptom as described in, for example, http://docs.info.apple.com/article.html?artnum=95037 is:
Quote:
Important: Be very careful when handling the main logic board. Remove the battery when handling the logic board so the PMU is not affected. The PMU is very sensitive and touching the circuitry on the logic board can cause the PMU to stop responding. If the PMU stops responding, the battery life goes from about five years to about two days if the PMU is not reset.
I would imagine that, however unlikely that might be, Apple surely gets a few service calls on it, and they're tired of having to pay for the repairs (even if all they spend is lost goodwill to the customer whose computer they refuse to repair under warranty).

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#1879 - 08/23/09 07:04 AM Re: Power Supply Puzzler [Re: ganbustein]
Virtual1 Offline


Registered: 08/04/09
Loc: Iowa
But the fix for crashing the PMU by early reset is ... to reset the pmu.

And considering how utterly devoid of feedback the reset process is and how unusual the procedure is, most people that try it that fail to get results will say "That didn't do anything, maybe I didn't do it right?" and will just try it again. (which would fix said problem)

So I really wonder just how often they run into this?
_________________________
I work for the Department of Redundancy Department

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