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Thread: LCD goes black intermittently after repair - everything else still functions

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I repaired an iPhone 4 that had water damage. The board was cleaned with 96% alcohol. Same as I would do with a damaged laptop board. I also replaced the
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  1. #1
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    Default LCD goes black intermittently after repair - everything else still functions
    I repaired an iPhone 4 that had water damage. The board was cleaned with 96% alcohol. Same as I would do with a damaged laptop board. I also replaced the battery.

    The problem I have had is that I can turn the phone on and it will come up and everything is fine and dandy. Then suddenly it goes black. Everything is still functioning and the touchscreen is still responsive. I can play music or even shut it off, and occasionally if I press the home button I will get a quick picture of the lock screen. I have had the problem with the original display assembly and a replacement.

    I actually got a few hits via google to others asking about this issue but in those cases there were no answers. Does anyone have an idea to the cause or better yet the fix for this situation?

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    Quote Originally Posted by mrvisserplein View Post
    I repaired an iPhone 4 that had water damage. The board was cleaned with 96% alcohol. Same as I would do with a damaged laptop board. I also replaced the battery.

    The problem I have had is that I can turn the phone on and it will come up and everything is fine and dandy. Then suddenly it goes black. Everything is still functioning and the touchscreen is still responsive. I can play music or even shut it off, and occasionally if I press the home button I will get a quick picture of the lock screen. I have had the problem with the original display assembly and a replacement.

    I actually got a few hits via google to others asking about this issue but in those cases there were no answers. Does anyone have an idea to the cause or better yet the fix for this situation?
    It could be a bad LCD but 99% chance that you answered the question in your very first sentence.

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    Quote Originally Posted by B-Roll View Post
    It could be a bad LCD but 99% chance that you answered the question in your very first sentence.
    Do you do liquid damage repair?

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    If you've cleaned the board already, that's about all we would do. I'd try another LCD just to be certain. There are 2 things that control the backlight on an LCD. The actual backlight on the LCD and the fuse on the board that tells the backlight to turn on. If it's the fuse on the board that's shorting out, then the chances or replacement are slim. Possible but slim. This usually happens with water damage.

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    Quote Originally Posted by B-Roll View Post
    If you've cleaned the board already, that's about all we would do. I'd try another LCD just to be certain. There are 2 things that control the backlight on an LCD. The actual backlight on the LCD and the fuse on the board that tells the backlight to turn on. If it's the fuse on the board that's shorting out, then the chances or replacement are slim. Possible but slim. This usually happens with water damage.
    My first instinct was the IC but I have gotten it up fully functional twice now. Holding down the home button often provides a flash from the screen. I have had the same symptoms with the original and replacement screen.

    This doesn't appear to be a backlight issue where there is a faint picture but no backlight. It is a black screen.

    Would a short allow the LCD to boot fine occasionally?

    edit: one thing I haven't done yet is restore.

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    If you press the home button the display flashes on showing a perfect picture but just for a moment. Sometimes the power button also accomplishes this. A short would make sense in this case, right?

    I could use some advice on taking off the emi shield on the board. I would like to get a closer look.

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