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Logic board reset may repair non-functional FireWire System
I had an issue where my FireWire stopped working -- it would not recognize an external drive, a CD-R/CD-RW drive, nor an iPod. This remained true even after I purchased a new FireWire card (which I was able to return).

So after some troubleshooting (trying each device on its own), and then plugging the iPod into the CDR/CDRW or the External drive without any connection to the G4, neither would charge it. I then tried zapping the PRAM, but this also failed.

I then took a "risk" and pressed the disrupt button on the motherboard to completely reset all settings on the board. Bingo! Now all the drives work, and I am able to use all three together -- the external drive daisy chained through the CDR/CDRW to the G4, and the iPod directly to the G4. Hope that this may help somebody out there; it seems the FireWire thought it was no longer communicating with the drives, but the reset started it back up again.
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Logic board reset may repair non-functional FireWire | 15 comments | Create New Account
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Logic board reset may repair non-functional FireWire
Authored by: billabOng on Dec 08, '03 03:01:48PM

Why would you say this is a risk? This is part of my standard troubleshooting procedure once things like disk repair utilities or PRAM zapping fail.



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Logic board reset may repair non-functional FireWire
Authored by: Tom Dineen on Dec 08, '03 08:45:06PM

I say take a risk as if done improperly as the other post states it can cause more troubls, so, I mean"risk" as in use it catiously, and as it resets the clocks and confuse people who haven't done it before as to what exact preferencess it resets. Also anytime someone isn't to comfortable with tooling around inside there mac should cnsider anything they do as risky as they may bamage their components if not cautious.



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Logic board reset may repair non-functional FireWire
Authored by: lantzn on Dec 08, '03 03:14:03PM

This happened to me this morning on my dual 1GHz G4. I read in the AppleCare Sherlock menu about resetting the PRAM and NVRAM, tried that but nothing. Then I saw something about resetting the PMU button should you be having hardware issues. Since neither of my fw drives were mounting in either OS9 or OSX, I figured it was a hardware issue with the fw ports. I shut down, pulled the power cord, pulled the battery and checked it for 3.5 volts (check was good), reinstalled battery and waited 60 seconds, pushed the PMU button on the mother board with my finger and held it for 60 seconds. Rebooted and drives were back again. It's important to hold the PMU button down for awhile because the first time I tried this I only briefly pushed it and let go and drives did not appear. It did say DO NOT press the PMU button more then once during the process because it could cause major issues. I figured booting up completed the process and so I shut down and went through the process a second time holding the PMU longer the second time around.



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Logic board reset may repair non-functional FireWire
Authored by: timbloom on Dec 09, '03 02:23:11PM

Apple says to hold that button for "less than a second". Otherwise it will either drain your PRAM battery, or it will shorten the life of it dramatically.



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Logic board reset may repair non-functional FireWire
Authored by: gl@ on Jan 25, '04 09:54:27AM

Where is the PMU button ?



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Logic board reset may repair non-functional FireWire
Authored by: dfa4 on Dec 08, '03 11:09:48PM
If possible, how does one reset the logic board on the Power Mac Cube? Would appreciate any assistance.

--
Duane Andrews
http://www.people.cornell.edu/pages/dfa4

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--
Duane Fitzgerald Andrews
http://www.people.cornell.edu/pages/dfa4

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Logic board reset may repair non-functional FireWire
Authored by: johnsawyercjs on Dec 09, '03 12:12:27AM

To reset a G4 Cube's PMU:

• Unplug everything from the Cube (including its power supply), then remove the internal assembly from the Cube (turn the Cube upside down and press its plunger down until it unlocks, then pull up).
• Remove the video card and the riser card it's plugged into.
• Reinstall the riser card into the logic board (don't know why Apple says to do it this way, but that's what they say).
• Press switch S1 on the logic board, for about five seconds. It's a small, quarter-inch square part with a small black button in its center, along one edge of the logic board, not too far from one of the logic board's corners. You don't need to remove the battery, but if you have a current meter, measure the battery's current level, which is a more reliable way to tell if a lithium battery is good than measuring its voltage, which can still measure full voltage, but be unable to deliver any more current.
• Reassemble and see what happens.



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Logic board reset may repair non-functional FireWire
Authored by: Saint1 on Dec 08, '03 11:48:59PM

Resetting the PMU is a standard troubleshooting step when dealing with all hardware issues. The PMU (Power Manger Unit) is basically a computer inside the computer that handles the power flow throughout the system. There is no risk in resetting the PMU. Just don't press it more than once between restarts. Also, You do NOT need to hold it down for 60 secs. because this can also cause problems. Sometimes it needs to be reset more than once (reset PMU, restart, reset PMU again, restart...) to resolve the issue.

Another thing, Macs have LOGIC BOARDS, not mother boards (PCs)!



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Logic board reset may repair non-functional FireWire
Authored by: cryptlib on Dec 10, '03 12:00:53AM

And servers have mainboards, eh?

Where is this PMU reset button? I never heard of it before reading this thread. Anyone have an image?

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% kill -H -1



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Logic board reset may repair non-functional FireWire
Authored by: Saint1 on Dec 10, '03 11:12:49AM

It depends on what computer you have. Let me know which computer you have and I will tell you where it is.



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Logic board reset may repair non-functional FireWire
Authored by: blaze1600 on Jun 07, '04 01:22:12PM

I read your offer re helping identify this PMU button on the motherboard as I am having this same Firewire Drive non-recognition problem as well.

I have a Beige G3 desktop. Where exactly would I find this button.



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Logic board reset may repair non-functional FireWire
Authored by: louiezeng on Aug 02, '04 01:12:16PM

I have a PowerMac G3 Blue & White. Where would PMU button be? Thanks.

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LZ



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Logic board reset may repair non-functional FireWire
Authored by: ScottMcGerik on Dec 10, '03 09:20:39PM

Thank you for the hint! You saved me a trip to the repair shop. I thought I had bad FireWire ports after my LaCie FireWire drive stopped mounting on the Desktop. I even looked in the /dev directory to see if it was being recognized as a connected device (normally it is disk1), but it was gone.
After I reset the PMU, the drive light started flashing as I rebooted my iMac. When I logged in, the drive was mounted on the Desktop.

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http://mcgerik.com/scott/



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Logic board reset may repair non-functional FireWire
Authored by: louiezeng on Aug 02, '04 10:38:04AM

Can someone tell me where the PMU button is?
My firewire drive and internal CDROM did not show up on desktop at once. I would like to try this reset, but don't know where it is.
thanks,



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Logic board reset may repair non-functional FireWire
Authored by: fulviazag on Jan 29, '04 01:07:42PM

I have exactly the same problem with a scsi. Do you think that a Logic Board reset can "resurrect" a scsi too? If yes, how can I reset the LB of a G3 Lombard?
thanks
FZ



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