Model M6497 or A1005 / 500, 600, 700, 800, or 900 MHz G3 processor

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iBook won't power on after attempted PMU reset

Hi there. I recently purchased a used iBook G3 (700mhz/20gb HD). It was working fine for a week, and then all of a sudden, it died and no longer wants to power on.

This is the sequence of events.

It was having some battery issues -- the battery would show 30% or better charge, but it would go to sleep, as though it had no charge. Upon plugging it into the AC cord, it would then show 0% charge (until it fully charged, of course)

I attempted to reset the PMU by powering off, disconnecting AC, and pressing the CTRL-OPTION-SHIFT-PWR combination. Nothing happened, that is, no tone, or change in light on the power cord.

From that point, the iBook would no longer power on at all. I tried with both the battery in, the AC cord connected with the battery, and the AC cord alone with no battery, and still no luck.

I tried attempting to reset the PMU again, with the aforementioned multiple formations.

I don't think it's the DC board, as the power cord continues to shine green whenever it's plugged in.

I don't think it's the battery, in spite of the battery charge level issues, it still shows a full charge when pressing the level button. Also, it still won't power up even with the battery removed and only the AC cord connected.

I'm not sure, but I don't think it's the logic board, as it didn't exhibit the flickering screen issue associated with the logic board.

The RAM and Airport card are seated properly, and I tried powering on with them both removed, and still no luck.

It was running Tiger 10.4.11

Any idea what happened here?

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What I found when dissassembling my G3 iBook was a faulty capacitor at the spot marked C91 on the motherboard. This is the thing that looks like a battery (and actually does the same purpose in this case). It was already leaking but nothing serious. Back in the days Apple would just swap the entire board, but you won't get a new board, at least not from Apple.

This capacitor is actually responsible for keeping the settings of the PMU alive for a while even with all power disconnected from the machine. So, when it finally drains (after some days) a "dead" iBook may come alive for no apparent reason, because the "stuck" PMU has finally reset.

The solution to this is to swap the capacitor for a new one, which is quite easy for those who are able to solder. Find a friend who can. The capacitor is rated at 0.33 F, 5.5 Volts and you'll be able to buy one online if you do a search for EEC-S0HD334H which is the part number for a Panasonic model. Any model with the same rating and mounting will obviously work.


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Hi! What you and Mayer describe is resetting the PRAM. To reset the PMU (which would definitely be a good step), with the power off, hold down the power button for 10 seconds until you hopefully hear a tone and see the sleep light flash.

I would shake the machine lightly to determine if you hear any loose screws. It's very common for a loose screw bouncing around to short out the board. Boards can be killed in this way, however more often than not they do power up again later. Obviously though in such cases it's important to get the screws out.

Similarly, if the memory cover is out, the metal Airport antenna plug very commonly will short out the computer by coming in contact with the RAM or various places on the board. So if it is flopping loose, I'd definitely hold it aside.

I'd also remove the battery while testing, both to kill power to the machine and let it recover from being shorted out (if in fact that's what's happened), and also to rule it out as part of the problem.

Also, as far as the weak battery issues, go to and download Coconut Battery, a free utility. It will tell you the true capacity of the battery and let you get to the bottom of that situation. If may have 30% left of what is only 1/20th of it's original capacity, in which case that 30% could be expended in a minute or two.


按维修分数 1

Ok so one thing that needs to be cleared up on this one the PMU reset he attempted to do is the proper way to do it on the unibody MacBook/MacBook Pro model computers. As this one has the removable battery to reset the PMU he would need to remove the power cord and the battery then hold the power button for 5 seconds.

As for the issue he is getting I do suspect the logic board based on the fact that the smu chip is integrated into it and we are getting no power through either an adapter connection or a battery connection.

If you can test the adapter on another mac to make sure it is working properly so that you can rule out that being an issue at all.

Best Regards,



按维修分数 1


New contributors are always welcome. Please find that this iBook came out, at the latest,10/2003. System Management Units, also known as SMUs, are a relatively new form of control subsystem. The units first appeared with Mac systems in the latter part of 2004. The SMU replaced the older power management unit PMU.

Just what I was afraid of -- logic board failure.

Xen, I don't believe what you describe as the reset for this computer is correct. iBooks don't have a PRAM battery, and instead rely on the regular battery. This is why an iBook's time resets if the battery and AC power are absent. Therefore when you pull the battery and AC adapter, the computer is not "awake" at all and therefore doesn't even notice the reset attempt. It's subtle, and they don't explain the reason, but Apple's iBook instructions for resetting the PMU leave out the "remove the battery" step. This is because they want you to leave it in so that the computer will be "awake" and the reset can occur.


That's control- option - shift "P" & "R" keys, not the power key. Zap the PRAM and tell us what happened.


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Unfortunately this is not possible in a no power situation.


Hello guys, i have a similar problem. :( I recently purchased Ibook G3 12" from Internet. When i first got it, it worked for about an hour and when i turned power off buton, and left it for about an half an hour on charger, i couldn't start it again. When i press power on button, i hear the chimes, but i don't see picture. Keyboard is responding, i can open CD case, and press Caps Lock an Num and see green lights on. Then, suddenly i managed to turn it on, after 100 times of trying, and i played some music, browse the internet etc :) When i turned it off, and tried to start it up again, there was the same problem again. :(( I managed to turn him on again after 100 times, and when i lifted it up so i can move it to another place, it froze and i had to restart it. The same problem appeared again. So, shortly, Ibook works, but i always spend about an hour trying to turn it on, and it's really booooooring to me :) Can anyone please give me some advice about what should i do? :)) Thanks for spending your time for reading my post :) Btw, i am from Serbia, so i can't send my Ibook to Apple Store in USA, or somewhere else :((


按维修分数 0

I reset the PRAM in my G4 and now it is stuck on first screen- apple with circle loading-- i guess trying to get to the welcome screen... please help.. what do I do?


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stay with your original question, I'll go there now and we'll proceed



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