Make my ibook LCD work

February 28, 2007 7:28 PM

Help me get my ibook's LCD working, please.

Okay, so here's the long story.

I recently purchased a Mid-2005 G4 ibook, without an LCD. I currently use a G3 dual-USB ibook, and happen to have a spare LCD (with frame, etc) laying around. I bought the G4 with the explicit intention of mounting the spare LCD on the headless G4 body, not unlike This project.

So, here's what I did -

1. Bought the correct LVDS cable and inverter cable (with no reed switch).
2. Opened up the old LCD, cabled it up with the new cables, and closed everything up.
3. Mounted it all on the G4.

And.... it didn't work. The backlight won't turn on.

So here's my troubleshooting process -

1. Switch out inverter board with known good. No change.
2. Switch out LCD panel with known good. No change.
3. Confirm that by leaving the back open, and sitting the damn thing in front of a light, I can see everything on the screen, and use the laptop. This means the LVDS cable is working.
4. Use a multimeter to check the inverter cable for continuity. Tests perfect.

I can't imagine why this isn't working. My guess is that I'm down to a logic-board problem? The pins on the logic board that are supposed to be feeding voltage to the inverter aren't, for whatever reason?

I'd love to ask the original owner what exactly he did to this poor machine, but I can't, really - he was a bit of an assbag, and screwed me a little bit.

So, I'd love some suggestions as to what's wrong, or to some apple hardware-hacking forums where someone might have an idea about how to go about fixing this. I know they're out there.

posted by god hates math to computers & internet (3 comments total)

Any chance that the actual cold cathode on the LCD is out? I'm not sure if the actual LCD and the cold cathode can be separated, but the cathode is mentioned (slightly) here.

If the logic board pins that give voltage are bad and not giving the voltage to the cathode...well, you may be completely screwed in that instance. Just tracking something like that down makes my head hurt, must less actually doing it.

Good luck, and let us know if you find exactly what's wrong in the end.
posted by plaidrabbit at 9:03 PM on February 28, 2007

The G3 iBook's backlight comes from its reed switch, which is a part the G4 has but that doesn't seem to perform the same function. I've had a ton of G3 iBooks come into my shop with dead backlight and the reed switch is 99% of the time the culprit. The G4s with the same problem almost always have bad LCD panels and now faulty reed switches-- I don't think replacing the reed switch in a G4 has ever worked for a missing backlight for me.

You might try using the reed switch that came with the G3. I can't tell from that Flickr set if that guy did the same thing, but I'd be interested in seeing if that showed any improvement. The MLB shouldn't affect any backlight problems.
posted by hollisimo at 9:06 PM on February 28, 2007

I know the cold cathode isn't out - it's part of the LCD, which I've switched out with a known good. In fact, the LCD that previously wasn't responding is in the ibook i'm typing on now.

And, I thought it was the asleep/not asleep that came from the reed switch? I can see how that would affect the backlight being on/off, but wouldn't that also affect other sleep functions? The G4 is definitely not asleep - I can type my little heart out via a light behind the screen or an external monitor.

I do have a spare reed switch or two, but I'll have to dig around, and hope I can get it connected. This model has (what I think is unique) the reed switch in the main body of the unit, just south of the arrow keys, rather than up in the LCD frame. I'm not sure where the pins are, but to actually swap out the switch, I'll probably have to do some permanent modification if I don't buy a new one.

And since you know, how exactly does the switch go bad? It's normally open, right? I'd be interested in how they malfunction.
posted by god hates math at 9:46 PM on February 28, 2007