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Fifth generation of iPhone. Repair of this device is straightforward, and requires screwdrivers, prying tools, and patience. GSM/CDMA / 16, 32, or 64 GB / Black or White.

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How to fix missing filters & capacitors on logic board?

I recently replaced the screen and digitizer of my iPhone 4S. After reassembling the iPhone turned on and connected to the computer but the screen was black (Apple logo during restart but no backlight) so I took to a technician who took it apart and spotted the problem:

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I tore off these components: C76, FL4, FL3 and C405.

I have a donor board with all of these components, but the technician told me that FL4 might be harder to resolder since the soldering point has also been torn and that he has to find where FL4 line on the logic board goes in order to solder a wire from FL4. Therefore I wanted to verify that the components I tore are the actually the ones I pointed out and if there’s any other way to successfully resolder the damaged components? Is the bridge the best solution for FL4?

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1 Answer

Chosen Solution

It also looks like C21 is missing.

You can get away with not replacing the capacitors but you need to replace FL3 & FL4. Thankfully, FL4 is the one with the damaged pads and not FL3. You will have to run a jumper from one of the components highlighted in red near the PMIC (U5) (below).

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To the connector (or capacitor C21) in this image. Ideally, you would want to find a way to wire up the FL4 as a a filter and protection circuit but if it can’t be done, then a direct connection will work.

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Thank you very much! I will let you know how it works and if I can I will upload pictures.

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Topo Ceni will be eternally grateful.
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