Replacement LCD for a G4 ibook

5 replies [Last post]
Joined: Mar 7 2007
Posts: 3

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 (from a G3 - they're the same part number, so it shouldn't matter? No change.
2. Switch out LCD panel with known good (from both g3 and earlier model G4). 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. So, 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? I read (pretty poorly) the voltages coming off of the logic board with an o-scope, and there's voltages on all 4 pins. Whether or not they're right, I don't know.

Suggestions? I've currently got it at a mac-repair place, only because they've (theoretically) got more resources than I do, more parts to swap out to try and find the source of the problem. They apparently haven't even touched it yet (after 5 days...) and I'm thinking about just getting it back from them.


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Joined: Jun 4 2004
Posts: 8
the light is broken

maybe the backlight itself is somehow broken...


de facto macoholic

Joined: Sep 16 2004
Posts: 274
Have you checked all the back

Have you checked all the backlight connections in the display casing and inside the main computer? The backlight on my old ibook goes off if the screen is moved to certain positions, but I've been too lazy to figure out exactly where the connection is bad.

Joined: Mar 7 2007
Posts: 3
Both checked

I know it's not the backlight - I've swapped this LCD into my functioning ibook, and it works just fine. In fact, 3 known-good LCD panels have been swapped in, and none of them worked.

iantm's picture
Joined: Apr 2 2005
Posts: 709
mid 2005 iBook G4 hmmm ...

I'm assuming that this is a 12" 1.33 or 1 14" 1.42 ghz model. If so, try to disconnect the reed switch (on top of the optical drive, connects to the logic board in the vicinity of where the trackpad connects. I'm thinking the issue is with the reed switch.


- iantm
ACPT & ACDT (long expired)
BMW Certified Technician

Joined: Mar 7 2007
Posts: 3
Already done...

Oh, did I miss that on my overview? It's been disconnected for some time. Definitely not the reed switch.