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My question is can i use an iphone 3gs Backlight IC not the coil… on a iphone 4? Would it function the same if i mount it properly, the 3GS backlight IC is slightly larger than iphone

The iphone 4 uses a PH-AS-IP-00001 and the 3GS a IC 109B. They are two different beasts, and as you already mentioned different dimensions. I am all for fixing things, but in this case I would invest $10 and get the proper IC and coil and not risking a destroyed logic board. Just my 2 cents, good luck.

The screen is very different more pixels to push.so i would think that it would be different on the inside.I have the same problem but it is just a generation jumped.I have a buddy with a oscilloscope and will be checking that asap.I could post a picture to see if they match with what you or someone else reports.

nope they are very different chips with different pin outs just get the right IC fyi this is how you do the soldering when you get the ic and coil parts repair video update okay this is a soldering repair video on iphone 4S backlight coil the whole soldering process is the same for iphone 4 http://www.youtube.com/watch?v=Bsk6rg0KX