Released on September 19, 2014, this 5.5" screen iPhone is the larger version of the iPhone 6.

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No display! Backlight works and phone boots. PLEASE HELP!

Hello, I have gone over just about everything I can think of. Checked in diode mode pins 1,3,8 and 11 all within spec. Replaced chestnut ic. checked for shorted capacitors and diodes (all good) with no luck. Even checked clock lines thinking long screw problems but they were okay. What am I missing?

Another thing I just thought of. When I replaced the chestnut ic the B3 pad broke off. B3 and B4 pads are bridged together on the board and there was just enough of a stub left I had hoped it would make connection. Could the B3 cause no Image if not making connection?? B3 is LCM Boost on the ic. I was thinking if I had backlight then it must be making connection, but now I am not sure?

Sorry, forgot to give you back ground info. Phone has always worked great until battery needed replaced. So I opened it up for the first time and removed screen and installed battery, afterwards had a hard time getting display again kept reinstalling lcd connectors and getting lines in display but finally got it reconnected and working again but every once in awhile lines would show for just a few minutes and disappear. So I figured it was just a bad cable on the lcd screen so I ordered a new screen and never had to install it until one day when I dropped my phone without the case and display went blank. Installed new screen and it didn't work, so replaced chestnut ic and then it started working but my flash to the camera quit working so I took it apart again to see what was loose and when I put it together again No LCD! aargh! This no display problem is driving me nuts!!! spent hours on it.

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B3 & B4 must both be connected as they are responsible for the charge pump. If you only have a stump, it's possible that the pad is not making contact with the IC and therefore the LCD driver can't boost the voltage up to the amount necessary for driving the LCD.

You will need to install a micro-jumper to give more contact area for a good connection.

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Great, Thank you!!! I will remove chestnut and repair the pad and report back with my results. The reason i wasnt concerned at first was because C1502 and c1529 had continuity between them so was thinking they were getting 2 traces from b3 and b4 but that isnt the case as they just have single trace to both.

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Well, it didn't work and now I have lost back light and I dont think it is booting. Unfortunately I dont have any new chestnut chips so I am building the solder pads up as much as I can. im waiting for a chestnut reball pattern that I ordered but hasn't shown up yet. It seems to soldering okay but cant say 100% every pin is making contact which apparently it must not be doing or I wouldn't have lost my back light and boot. Any ideas let me know.

Thanks.

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There's nothing really in common between Chestnut and BL, other than VCC Main. You may have applied too much heat and cause collateral damage to the board.

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Is there any place where I can learn how backlight and display cicuits work on iphone 6 plus? I repair other electronics so I know how circuits work and have microscope and all tools needed just need to learn how this circuit works. I have just received ZXW dongle and it helps but doesn't explain what chip looks for voltage to turn on the next chip to get end result. Or if you know any good learning sights online I would be greatful. If I could figure this circuit out it would make it so much easier to find the problem.

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Minho - Someone else mentioned earlier that backlight wont come on unless it detects image working? Now I dont know but if thats true wouldn't chestnut have to work in order to get voltage turn on for back light?

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