Detailed Logic Board Question. No Backlight.
I obtained a Macbook Pro 13 unibody with non functioning display (everything else works). I took it apart ad discovered that the LVDS cable end was completely destroyed. I ordered a replacement display assembly (complete with LVDS cable). I now have an image but no backlight.
Upon close examination of the components surrounding the LVDS connector I notice I have a component missing compared to a detailed photo of the same motherboard that I found on the net. I am not sure if this component might be a fuse that has been removed. I am trying to find someone who has one of these logic boards accessable that can identify what this part is supposed to be. I can provide a picture of the area of the board showing the part.
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Without a picture indicating what part you're missing we don't have a clue how to identify it.
Here is a picture. Doesn't seem to be a way to add pictures directly on ifixit unless I am missing something.
The part circled in red is missing on my logic board and under magnification it looks like it "may" have been on teh solder pads at one time. Given the white body I think it is possible that it is a fuse but I suppose it could be a resisitor. I don't think I have ever seen a cap in white.
Anyone with one of these boards out in the open could put a meter across it and tell me the resistance???
No one have a MBP 2009 open and could measure this for me?
I checked the voltage on both sides of the pads with the machine running and it is zero Volts on both sides. Makes me think it can't be a fuse....
OK. I am a little closer now. It turns out that this is a capacitor. Given the white body it might be a tantalum cap. One side is ground and teh other is probably driving the LED backlight. It measures 27V with display on regular brightness and drops to 14V when the screen dims. When you shut off the machine it slowly drops to zero as it discharges.
Next step is to determine what value the cap is and to see if I should have 0 volts on it when it is not populated. Feel free to chime in with opinions here....
Found the reference circuit for the National Semiconductor part and my guess is that this cap is the 4.7uF Cout in the datasheet. Now I just need to trace through the circuit and see if there is anything open circuit feeding the cap. Then replace the cap and cross my fingers.
Hopefully this info is helping others here who might have no backlight on their LED displays.
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