iBook G4 has bad power management chip

Discussion in 'PowerPC Macs' started by kahlil88, May 21, 2009.

  1. kahlil88 macrumors member

    kahlil88

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    #1
    My 12" iBook G4/1.33GHz only charges when turned off or in sleep mode. I originally suspected the battery and/or DC board, but after mentioning the flaw on a Craigslist post I got some feedback from a fellow Mac enthusiast, who believed the problem to be a bad power management chip. He told me of a group in Ohio that will replace the bad chips for $150-200, but since I'm not afraid to tear these computers apart, I was wondering if anyone here had advice (i.e. where is the chip located, and can I order it fairly cheap?).
     
  2. NewMacbookPlz macrumors 68040

    NewMacbookPlz

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    #2
    Chances are the chip is embedded in the logic board, meaning it'll have to be de-soldered and re-soldered in.

    I'd also wager you can't "order" the chip, but the guys that replace them buy old/used iBooks and harvest parts from those to repair other iBooks.
     
  3. ppc750fx macrumors 65816

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  4. clyde2801 macrumors 601

    clyde2801

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    #4
    I had the same problem with my 12" pb, which basically has the same architecture. Took it to my local authorized repair shop, and yes, the power management chip is separate from the logic board.

    Turns out in my case, the tech just installed the os...yeah!
     
  5. MacTech68, May 22, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #5
    Power Managment Units are generally a part of the Motherboard except for some earlier Powerbooks.

    What I'd check (apart from the suggestions already made) is to check which AC Adapter you are using.

    Make sure you have a 65W adapter and not a 45W AC Adapter.

    Better yet, try finding another 65W AC adapter that you can test with.

    Some PowerBooks will not charge the battery and run the machine simultaneously if you're using a 45W AC Adapter. I'm not sure if this also applies to the later iBook G4's but it's a possibility.

    The plug on the AC Adapter uses a pin to apply a small reference voltage that the iBooks and PowerBooks can use to determine which AC Adapter is connected.

    If the DC in board, the DC In socket or plug is faulty, the iBook's PMU may default to thinking that only a 45W AC adapter is connected and is acting in the safest manner.

    :)
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  6. kahlil88 thread starter macrumors member

    kahlil88

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    #6
    Wow, it turns out I actually have a 45W power supply! I'm so relieved this might be the entire problem, but I have yet to find a 65W power supply to test it with.
     
  7. Apple933 macrumors newbie

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    #7
    I currently have the exact same issue with my 12" 1.2ghz iBook G4... found this thread and thought I'd make a post. I've tried everything from a new battery to different adapters to different DC-in boards... all to no avail. Sent in the laptop to a repair company only to be quoted $200 to repair it. Used, working boards are cheaper than that on eBay. I have some experience with technical work with a soldering iron, so as a last resort I'm trying to replace the PMU myself.

    The only problem is that I haven't been able to pinpoint where the PMU chip is located on the motherboard. Based on numbers found on various chips, I think I've located a larger-sized one that might be it, but I can't get enough details online to be sure. The chip is located on the bottom side of the logic board almost directly on the other side of the hard drive. It's relatively large compared to those around it... maybe a bit smaller than the largest chips on the board. I don't have my iBook open at the moment to describe it any more or give chip numbers, but I'll work on that and see if I can post back in a bit.

    If anyone's got any further insight into this, please respond... thanks
     
  8. MacTech68, Jun 5, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #8
    I'd doubt that your PMU chip itself is the problem (though it IS hard to tell) but more likely to be a passive component somewhere like a resistor, capacitor or even a small diode or transistor.

    I recently took delivery of a Pismo PB that was dead and as usual with these it was completely dead. No amount of hitting the PMU reset would even get it to power on. Removing the internal rechargeable Lithium backup battery and the user battery and AC power source, shorting the internal battery connector on the motherboard for a minute, re-attaching the internal battery and connecting the AC adapter allowed it to power on.

    I wonder if the PMU's RAM can get stuck like this on other machines. It certainly does on other PowerBooks and the old LC475 and PPC 6100.

    Trouble is that later PowerBooks and iBooks use a "slow discharge capacitor" instead of an internal rechargeable Lithium battery which is soldered to the motherboard.

    They look like this

    There would be no harm in removing all power sources from the logic board and shorting this capacitor out for a few minutes (or overnight if you like). Then remove the short and re-attach just the AC adapter and power on. After a boot-up and shut-down, attach your user removable battery and see if that helps.

    Also, regarding the AC adapter detection, this uses the outer ring on the adapter's DC plug. When plugged in, from a known ground point to this outer ring should get you a small voltage as referenced in this Apple Tech Article.

    If it were me, I'd be tracing that small voltage to see where it goes. Having a complete working iBook would help to check noticeable differences in component values in situ.

    Here's hoping.
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  9. kahlil88 thread starter macrumors member

    kahlil88

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    #9
    Interesting...perhaps I'll have a look at that capacitor the next time I tear this machine apart. I borrowed a 65W power adapter and it didn't make a difference.
     
  10. MacTech68, Jun 9, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #10
    Well, at the very least, that eliminates the AC Adapter as a cause.

    Some additional information. In System Profiler, click on the "Power" sub-heading in the left-hand panel and then scroll the main panel down to "AC Charger Information"

    In MacOS 10.4.11 on my 1.42Ghz iBook I see:

    and this is with a 45W Adapter.

    Referring back to the Apple Tech Article, the table at the bottom shows the 65W, 45W and the "Aircraft".

    The reason for posting this is that further research showed an iBook G4 reporting:

    which could be that the PMU chip isn't getting any reference voltage and defaulting to the lowest "safe" setting. Again, this could be the DC-in board or a passive component on the logic board. One case suggests the screw holding the DC in board as being loose - worth checking.

    Also, I'd be interested to see what "Watts" are reported for a 65W AC adapter.

    :)
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  11. kahlil88 thread starter macrumors member

    kahlil88

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    #11
    Opened up the iBook again today and discharged the capacitor, but it still won't charge while I'm using it. Here are my power specs in System Profiler:
     
  12. MacTech68, Jun 11, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #12
    That would seem to indicate that the PMU chip isn't receiving the reference voltage that tells it which model of AC Adapter is connected. Further research shows that a 45W AC adapter will show "50" (as mine does) and a 65W will show "65". :rolleyes:

    This might be a common failure but I'd need a faulty iBook to go much further. Does anybody have the chip numbers from what is believed to be the PMU?

    If I ever upgrade my 60GB internal HD (I use external Firewire drives for storage), I might be tempted to try and trace the reference voltage circuit.

    (if anybody wants to send me a working 200GB 2.5" PATA drive I would be VERY temped)..... :D ;)


    EDIT:
    Looking at pictures online of the DC In board's connection to the logic board, on both G3 & G4 iBooks it's an 8 pin connector. 3 carry the 24V, 3 are GND and the two outer connections must be used for the voltage ref and something else.

    EDIT 2:
    Have a look at a chip labeled with "U42" (printed in white on the logic board next to the chip). It's right near the front edge of the logic board near the spring for the display release button. It's a small 8 pin IC. See if that chip or nearby components have any corrosion or cracked solder joints. You might need a jeweler's loupe or other powerful lens.

    EDIT 3:
    The chip at U42 is a Maxim "MAX4172EUA" current sensing amplifier and may be marked as "4172EUA".
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  13. MacTech68, Jun 16, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #13
    Just a post since I've just noticed that edits don't push out an email notification.

    :)
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  14. kahlil88 thread starter macrumors member

    kahlil88

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    #14
    I replaced the DC board with a known working one, so I can officially confirm that's not the problem. The chip looked fine (no burns or cracked solder joints), but I cleaned the area around it with alcohol anyway. What should I do to test if the chip is working?
     
  15. MacTech68, Jun 27, 2009
    Last edited: Jan 30, 2011

    MacTech68 macrumors 68000

    MacTech68

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    #15
    Ahhh... there you have me. I don't know. :(

    What I'd be curious about is (if you have a Multimeter) is to check what the voltages are on the outer two pins of the DC in board connector on the logic board when the AC Adapter is plugged in and when it's not plugged in. It would also be handy to check those voltages and compare them with a 65W AC Adapter and a 45W AC Adapter. One of those two outer pins (I don't know which) is the "sense" voltage which tells the logic board which model of AC Adapter is connected.

    If you don't have a jeweler's loupe to check for cracks in solder joints and you are handy with a soldering iron on TINY components, you might want to try reflowing the solder on that chip. If you've not soldered TINY components successfully before then I recommend you DO NOT attempt it - it's not easy. :eek:

    The reason I mention that 8 pin chip is that I found a forum posting elsewhere with a G4 iBook with similar symptoms and the person posted pictures of that chip with one or two pins badly corroded. I looked up the chip to find it's a current sensing device.

    It's difficult to recommend much more without a "donor" iBook here and my own iBook is in constant use recording TV shows. Don't get me wrong, I'd still like to help resolve this as it seems to be a common issue with iBook G4s. :)
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