iBook G4 12 inch Logic Board Issues - The definitive Guide

Chances are that if you're reading this, you have an iBook that isn't working properly. For the last two years, I have been supporting a deployment of 2k plus iBook G4 12 inch computers. If there is an issue that could rear its head on these machines, chances are good that I have found it. I'm going to break this guide up into a few sections - symptom charts, what parts work in what machines, and whether it's worth doing the work yourself. I will refer you to the excellent take apart guides that the folks at www.pbfixit.com have available. I could talk you through the take apart process, but it would be long and drawn out - something I'd rather not go through. And while I am very knowledgeable in this area, I take NO liability for your actions or any results that may come from this guide. The information is reliable, but any time you crack into your iBook - it is at your own risk.

We'll start with the symptom chart. Here it is below.

Gray Screen on boot
- This could be a logic board, lvds cable, or a bad hard drive. To isolate the issue, try to connect an external display - if the issue persists on the external display, we've just ruled out the lvds cable. Next try to boot the machine into open firmware mode (hold down apple, option, o, f during boot) - if you can get into the open firmware prompt you have a bad hard drive and a good logic board.

No video/no backlight, but the computer chimes upon power on
- This could be the reed switch/inverter cable (second most common cause), logic board, lvds cable, or corrupted pram (most common culprit). Start by zapping the pram (hold down apple, option, p, r upon power on, wait for computer to chime three times before releasing these keys). After the third chime, reset open firmware (go into Open Firmware by holding down Apple, Option, o, f upon power on - when in open firmware, type reset-nvram then press enter. Next, type reset-all and press enter, the computer should restart now and work fine. If this does not work, hook up an external display - if that is getting video then there is an issue with the lvds cable. If there is no backlight on your internal display, after doing these steps and you can get video on the external display and internal display (but with no backlight), the reed switch/inverter cable needs to be replaced. If you can't get anything on the internal or external display - your logic board is the culprit.

Computer powers off when the lcd is tilted back
- This is from either the LVDS cable or reed switch/inverter cable. Remove the bottom case of your computer, and disconnect the reed switch/inverter cable from the logic board. Power on the computer in this open state, and move the display. If the computer powers off, the culprit is the LVDS cable. If not, you've already isolated the issue and the reed switch/inverter cable needs replacement.

Computer freezes or locks up when moved
- This is commonly caused by loose screws and/or warped/cracked frames. Unfortunately, this issue can easily go from being purely structural to being one where logic board replacement will be required.

No video/no backlight/no chime on power on
- This is guaranteed to be a bad logic board. Sometimes, a PMU reset can fix this issue, but it will come back.

Now for the parts Compatibility guide. Chances are that you've got an 800 mhz or 1ghz iBook G4 and would love to get a speed boost while you're in the process of fixing your iBook. Here's where I'll go over which models have commonality, and which ones don't, in addition to which parts are compatible. Since this seems to be a frequent question, it's only fair to cover this. All LCD panels in iBooks will work in other machines, so any panel from a dual usb or iBook G4 will work.

800 mhz / 1ghz iBook G4
- The 800 mhz machines can easily be upgraded to a 1ghz model with little difficulty. When moving from an 800 mhz board to a 1ghz board, you will need to replace the fan, the modem, and the heatsink. (you only need to replace the heatsink if you need a modem - the modem from 800 mhz model won't work with the 1ghz board). Other than that, it's easy to do. To upgrade one of these to a 1.2 or a 1.33 involves replacing everything on the computer, save for a few screws, the hard drive, and the optical drive. For the money, a newer iBook or MacBook is a better investment unless you somehow find a newer iBook with a cracked LCD and no other problems for very cheap. These are the last machines with an ADB trackpad.

1.2 ghz iBook G4
- This machine is something of an odd duck because it has very little commonality with any other machine. Don't bother upgrading it because you will essentially be replacing everything on the lower half, save for a few screws, hard drive, and optical drive. Unless you can get a 1.33 with a cracked lcd for very cheap, don't bother trying to upgrade. Apple made the jump to USB for the trackpad on this model, so this top case will work with the 1.33's, but that's about it.

1.33 ghz iBook G4
- this is the end of the line for the iBook G4. No upgrade room. This is a very odd machine. Nothing, short of the hard drive, lcd, and optical drive will work with other machines. The top case on this machine will only work with the 1.2 ghz iBook G4's as well.

Now, for the is it worth it section. If you're looking to spend $500 or more to fix your iBook G4, try to save a little more money as the 1.33 ghz iBooks are selling for less than $800 new at resellers that still have them. Even cheaper used. If you can get the parts and feel comfortable doing the work yourself, I would say that it would be best to spend no more than $300 total on parts. 1.83 ghz white MacBooks can be had for between $900 and $1000, so that's another thing to keep in mind. It really doesn't make too much sense to keep throwing money into a machine when for not too much more, you can get a comparable new machine with a warranty.

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