10-27-2010, 08:00 PM

Hi,

I have a 2008 MacBook (A1181) and am having one issue that I can't seem to figure out. A few weeks ago, the backlight started giving me problems. Specifically, it would shut off. Apple wanted $300 to fix it and I'd rather just get a new computer at that point, so I thought I'd try and fix it myself. If I break it, oh well.

Anyway, I ordered a new backlight inverter board and an inverter cable, but the problem persists. If I leave the computer alone completely, the backlight turns on after about a minute of sitting at the login screen. However, as soon as I touch a key/move the mouse, it shuts off. If I wait again, it comes back on a minute or two later, but then the same thing happens.

I've tried an external keyboard and have gotten the same results.

Any ideas at all what could be causing this? Or is the hardware just messed up?

10-27-2010, 08:34 PM

I'm a Mac newbie, but it smells to me like it may be a software or firmware problem judging by the symptoms you describe.
I suggest you try a post on the OS forum.

10-27-2010, 10:30 PM

The reason Apple wanted $300 to replace the backlight is because it's a difficult repair requiring quite a bit of labor. The entire LCD casing has to be disassembled. Your trouble is not with the inverter, it's the CCFL tube that's bad. The inverter feeds it AC power which in turn lights the CCFL that provides the back lighting for your LCD.

Recommended repair for a bad backlight is to replace the entire LCD assembly. It's actually less work and only costs a bit more. See the entire procedure at iFixit: The free repair manual.

10-28-2010, 01:40 AM

Yeah I can buy an entire new LCD assembly for $119 and I wouldn't think Apple would even bother taking apart the screen to get to the backlight; they'd probably just swap the entire screen.

The only thing that weirds me out is that the backlight works briefly, but as soon as I hit a key it shuts back off. Then it'll come back on a minute later and do the same thing. I plugged in a USB keyboard and got the same result. It also shuts off as soon as I move the mouse. Really, really weird. If I leave the Mac alone, the backlight will shut itself off a minute or so later, but I'm thinking it might be doing that simply because it thinks the backlight has been on the entire time and it's dimming the backlight as a result of inactivity.

I wouldn't mind taking the plunge for the screen, I just don't want that to end up not being the problem. But after swapping out the inverter board, backlight cable and LCD, I guess that only leaves the motherboard as a potential culprit.

Edit: When I say it works "briefly" it never works throughout the splash screen and then it won't work for a few minutes on the login screen, but a minute or so later it will randomly turn on, then turns off the second I make an input (or if I leave it alone for a minute, it shuts off again.)

10-28-2010, 02:37 PM

As a "shot in the dark" try resetting the System Management Controller if you have not already done so. LINK The SMC controls the backlight turning on an off for sleep and power saver mode. Could be that it has become confused. Let us know.