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Released September 16, 2016. Models A1661, A1784, and A1785. Available in 32, 128, or 256 GB configurations in Rose gold, gold, silver, black, jet black, and (Product)Red.

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Is the phone damaging the backlight on good LCD's?

I replaced the LCD for a customer and a couple of weeks later he reported the left side of the display to be dim. Note that the battery was unplugged during the repair and there were no signs of liquid or physical damage inside of the phone nor on the LCD prior to the initial repair or when he brought it back in.

I replaced that screen under warranty assuming that it was a defective LCD. The newest replacement LCD worked fine at first. But, a couple of hours later he reported the BL went out on the right side of the second LCD replacement.

I'm pretty sure I didn't have two defective LCD's both with BL issues. I tested the first replacement LCD on a tester phone and the BL was still out on it. It seems then that in both cases, I put a good LCD on the phone and that the phone somehow eventually damaged the backlights on each LCD. I've not experienced this particular issue before. Has anyone?

I have only seen BL circuit blown out from people not unplugging the battery during a repair in which case you see the backlight issue as soon as you connect a new screen. Or when the solder joints make contact with the back shield. Neither was the case in this situation.

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I would consider as well the possibility that the iPhone backlight circuit is damaged..has that been thoroughly tested ?


I haven't fully explored the BL circuit yet. However, from my experience and thinking I would generally see the BL issue immediately on connecting the new LCD and powering up the phone if the BL circuit was damaged. In this case the backlight seems to partially go out without any flickering over time.


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There are two possible scenarios that I can see:

  1. You possibly have a bad batch of LCD’s. You’ll want to look at this carefully in terms of batch/vendor etc.
  2. If this is a logic board issue, then I would look at the backlight filter. This is a Ferrite Bead and the purpose of using a FB is not to act as a fuse but to filter out high frequency noise. A FB will let DC pass but filter out high frequency noise. When there is too much noise on the line it becomes resistive (whatever the spec says, i.e. 33R). Perhaps this phone has been repaired in the past and someone just jumpered the filter instead of replacing it meaning that high frequency noise is getting to the actual backlight.
  3. Otherwise, if the screens are good then you may want to wipe the entire BL circuit and rebuild.

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Thanks for the response. The two LCD's are from the same vendor but from two batches that are about 6 months apart, so it seems improbable, although not impossible, to me that the two LCD's used on this one phone would have the same defect, which I have never experienced with other LCD's on other customers' phones.

I'm more interested in your second scenario concerning high frequency noise reaching the LCD. There has been no repair work on the phone other than my screen replacement. I wonder if there might be another scenario in which high frequency reaches the LCD and compromises the backlight.

Also, on the first replacement, the dimming was on the left side of the display, and the customer said that it occurred about two weeks after the initial repair. This time the dimming occurred about 20 minutes after he left my shop and is apparently occurring on the right side of the display. I wonder if the switching of sides on which the backlight is dimmed indicates anything to you about a possible cause.


The side of the backlight is probably more related to how the screen is built. From a circuit point of view, there is no "weak side".

My hope was this device had been worked on before. Then my hypothesis becomes possible. If it's all original, then probably not. :>).


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Gregory Harris zal eeuwig dankbaar zijn.

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