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iPhone 6S no image

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  • #1

    iPhone 6S no image

    Hey guys, looking for some pointers and troubleshooting advice on an iphone 6S which HAS backlight, but no image. Confirmed booting fully through iTunes detection, had a broken screen that the customer said happened a while back and just went no image one day, so I assumed LCD had just given up. Alas, that's not the case.

    So what I'm struggling with here is that there is no short, or at least no full short. PP5V7_LCM_AVDDH is low, diode mode reading about .220, but everything else seems good. The MIPI lines are a little high, .55 ish consistently but I'm not sure if that's anything to be concerned with, or if I can even do anything about that as they run a short path to the CPU anyway.

    So do I look at Chestnut replacement, or a partial short on one of the 5v7 caps? Or am I missing an obvious clue or test I should be running elsewhere? I've researched as best I can but everything else I've come across has a nice handy full short or bad filter. I have replaced the filter FL4200 to no effect.

    Thanks in advance.
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  • #2
    Originally posted by AGibb View Post
    Hey guys, looking for some pointers and troubleshooting advice on an iphone 6S which HAS backlight, but no image. Confirmed booting fully through iTunes detection, had a broken screen that the customer said happened a while back and just went no image one day, so I assumed LCD had just given up. Alas, that's not the case.

    So what I'm struggling with here is that there is no short, or at least no full short. PP5V7_LCM_AVDDH is low, diode mode reading about .220, but everything else seems good. The MIPI lines are a little high, .55 ish consistently but I'm not sure if that's anything to be concerned with, or if I can even do anything about that as they run a short path to the CPU anyway.

    So do I look at Chestnut replacement, or a partial short on one of the 5v7 caps? Or am I missing an obvious clue or test I should be running elsewhere? I've researched as best I can but everything else I've come across has a nice handy full short or bad filter. I have replaced the filter FL4200 to no effect.

    Thanks in advance.
    Do you have a working 6s or ZXW to compare readings? Sometimes ZXW is off a bit so a working one is best. If they match at the connector, try very carefully bending the pins just a small amount so that they contact better with the LCD screen connector. I've seen worn out pins cause no image. If that doesn't work and the values matched, yeah chestnut would be my next suspect.

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    • #3
      Thanks for the response John. I have ZXW and am comparing readings to that with margin for error/variance, but also comparing to a known good, which reads close to the ZXW numbers anyway. Unfortunately the reading is out at the connector, so pins askew is ruled out, not to mention they look flawless. I did also see a video on the pins causing no image in my research and am certain that is not the case. I guess I'll replace chestnut and see where that takes me.
      Last edited by AGibb; 07-16-2018, 03:00 PM. Reason: typos

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      • #4
        So chestnut replaced, and still the same result, and the same reading, up to .229 so a negligible variance. No image only, backlight is good. Any other suggestions?

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        • #5
          Anybody got any ideas? About to call this no repair so even a long shot is worth it at this stage!

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          • #6
            Is .229 normal? No. Is it anywhere close to normal? No.
            What is the problem when a line has a low diode mode reading? A partial short. What kinds of components can be the cause of a partial short? Only caps or chips. Is this line required for image? Yes. Does this line commonly fail out of the blue after drop? Yes. And what is the common cause of failure, chestnut or bad cap? Bad cap.

            So what should you have done here right out of the gate before anything else?


            (Also a note while reading above —getting a good diode mode reading at the connector does NOT rule out a problem with the connector pin and screen. I don’t think that’s what is going on here, but I wanted to correct that thinking.

            carry on!
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            • #7
              And we have image.

              Thanks Jessa, confirming one of my initial suspicions and giving me the kick in the ass to go with my gut instead of second guessing myself. Partial short on C2400.

              Going forward, any advice for finding the culprit other than removal trial and error?

              Comment

              • Jessa_the_Professa
                #7.1
                Jessa_the_Professa commented
                07-24-2018, 10:56 PM
                Editing a comment
                there are only three possible and it is the one on the end 80% of the time, so knock him off with a razor on any phone with that presentation for a 10 second fix
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