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iPhone 5 low resolution and blur image in every lcd

I have a customers iPhone 5 that dropped from his hand. When I received the phone I thought it was only the LCD that need replacement, I put other LCD but still the phone has low quality image, low resolution and blur image. I replace the LCD again but still the same, I test the LCDs in other iPhone 5 and working great. I checked the FPC connector and has no damage. Can you please help me, what do you think is the problem? Is there any damage IC? Any damage resistor? Where I suppose to look?

Please take a look at this photos

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Update (02/21/2017)

i inspected the motherboard with the microscope and i find one missing part. Please see the photos and advise me what to do

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This missing part seems to be the Capacitor C440. Do you think this cause the problem? How can i fix this? Is it neccesary to find the same capacitor? Is this capacitor polarized or i can install it in any direction?

Thanks for your help!!!

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So you confirm that the screens do not work on this customer phone but work perfectly on a different phone? That is odd. I would double check the connector again under high magnification. Look at the soldered pins and the seating area inside.

The LCD image is driven directly by the CPU so it's not like there is an image IC to replace. You could also look at the LCM CONNECTOR page of the schematics. You will note that all of the lines are filtered by either a choke or a ferrite bead. Maybe one of them is not working properly and causing issues on the display.

Using a multimeter, they should measure zero or very low (<1 Ohm) resistance. Their role is to filter out high frequency noise and they can get very resistive at high frequency. But for normal DC voltage (0 or 1), they act like a wire.

It doesn't appear to be a backlight issue but double check that too. Take a look and get back to me with more details.

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The connector is perfect, nothing strange, no damage pins and nothing unusual inside. I will test the LCD filters and resistors near the LCD connector and i will come back.

из

Hi John. Normally I'm not too concerned about this type of capacitor. It is a 56pF/6.3V ceramic (or MLCC) capacitor. They are very common on iDevice logic boards so you could easily harvest them if you wanted or you can order them from Digikey (note, you would have to get the 16V version).

However, because the capacitor and ferrite bead form an RLC circuit with the load, there may be some filtering activity going on here. Your screen blurriness is quite subtle so it may be be caused by something "minor", just like a missing 56pF cap.

So I would encourage you to replace that capacitor and double check all the other components to see if they are solidly anchored in place.

из

I really don't understand what is going on. I replaced this capacitor from other boards capacitor and still no quality image. I should test filters and resistors? I try to measure some capacitors and my multimeter shows a Diode but schematic write capacitor!!! Iam so confused with this phone

из

As I originally suggested in my answer:

You could also look at the LCM CONNECTOR page of the schematics. You will note that all of the lines are filtered by either a choke or a ferrite bead. Maybe one of them is not working properly and causing issues on the display.

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How can i test this parts? How can i know if this choke or ferrite bead causing this problem?

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This is the schematic, i marked the filters, resistors, capacitors that connected straight to the LCD connector with yellow color but i don't know how to test them. How do i know what filter causes this problem?

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see my comment above...

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So i check the Ohm of this filters and if the result is filter > 1 Ohm, that means this filter causes the problem??

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At DC voltages, a ferrite bead should measure near zero Ohms (tenths of an Ohm).

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