I'm not sure my problem is exactly the same because I have completely dissassembled my iBook (Pics coming soon). When I flex (bend ever so slightly) my mobo, the screen comes on fine. When i unflex it, the backlight goes back off. You can tell the image is on the screen, but the backlight just goes off. Now when you plug in an ext monitor, it works fine too.
I'd love to figure this out, but I've already decided this iBook is going to be used for something creative...mostly because I'm too lazy to put it back in the case.
Unless you have spare parts to test, your best bet is to look for a repair centre who will diagnose your machine for free, no fix no fee. The reed cable is quite cheap to have done, I would imagine the inverter would be next cheapest. The backlight is a fiddly job, so the labour costs will add up.
Does yours qualify for the motherboard recall? (Serial between UX114XXX and UV341XXXX - double check this range, I'm going from memory) If so, thats the cheapest of all, since they will do it for free if its less than 3 years old. The fact that you can flex the mobo to 'toggle' the backlight suggests to me that the mobo is actually the most likely candidate. The recall was due to fault gfx chips I believe. Its not usually the backlight they affect, but often pressing the chip would cause screen problems to appear and disappear. If you have to pay for a new mobo, its a job for eBay, since ordering one from Apple, even if you fit it yourself, will cost almost as much as a new 12"......
Sory to be the bearer of bad news, but I could be wrong.
I believe that this one is more than three years old now...sigh...it was eligible for the mobo switch and it had already received the new one. Its weird tho that I can view video fine on the VGA out at all times. I've checked the cables. I believe its something on the mobo.
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