Backlight LCD display not working, how to fix it?

The backlight on my iBook g4 is not working.

Symptoms:

  • external screen works
  • iBook runs normal
  • Apple Hardware Test cannot find any problems
  • Screen brightness is at full
  • LCD screen works except the backlight. If I shine at the screen with a flashlight I can see all that all the pixels are working and showing the same image as the external screen.

I have tried the following:

  • changed inverter board
  • changed inverter cable, this cable was most likely the original problem. The insulation on a few wires was completely gone.
  • changed the LCD panel for one with a know working backlight.

Does anybody have some tips on how to repair my beloved iBook? Does anybody know where to look on the logic board?

Thanks for reading and all ideas are welcome.

Arjen

Answered! View the answer I have this problem too

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Nicely worded question. +

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You say <<...changed inverter cable, this cable was most likely the original problem. The insulation on a few wires was completely gone...>>.

Most likely the inverter cable shorted in the hinge and blowed the logic board's microfuse that protects the inverter circuitry. I've been able to find the microfuse location on the 1197Ghz, 1.2Ghz and on one of the two 1.33Ghz revision models. Look at the left of the inverter socket on the logic board, the microfuse has letters TH written on it. Use a multimeter and check the continuity. If there's no continuity then the fuse is blown. Bridging the microfuse with a wire should restore the power to the inverter socket then to the inverter board and the backlight if nothing else is damaged on the logic board.

Block Image

http://www.flickr.com/photos/61008642@N0...

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lemerise, thanks for the answer. I'll let you know if this will solve the problem.

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Great information Lemerise! Now if I could only find the microfuse location on a 12" G3! :-) Would you expect it to be labeled TH on a G3 as well? Thanks!

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Sorry rdklinc I checked many iBook G3 boards but never found it. The iBook models I specified in my answer are the only ones I can locate that bloody microfuse. Again boards diagrams would be very helpful if availables somewhere. On other G3/G4 boards they use another form factor microfuse that should be located near the inverter port but where ????

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if you've changed the Inverter Board, Inverter cable, and the LCD panel.. unfortunately all that is left is the Logic board.

Was the iBook dropped or subject to a liquid spill?

as you know.. the backlight is inside the LCD panel..

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your right. I missed that in his question. I'll delete my response. +1

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greeeat healp it solved my problem on a g4 1.3 now i hope i put a really thin wire that burns faster than the board in case of a short. watch out for a chi mei screen cable compatibility issue which i think caused the trouble

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conwaybomber will be eternally grateful.
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