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Touch sometime does not work iPhone 7

Hi @refectio, hi guys, i need help !

recently i received iPhone 7 with bootloop issue and touch issue. So i placed C12 audio jumper and i found, than touch does not work. So i tried:

reball HOMER 

replaced M2800

replaced U4805 because touch ID had damaged resistor (open line - infinity resistance) on I2C_MESA_TURTLE_SCL_CONN line.

Touch connector resistance OK

LCD connector resistance OK

Where can be problem?

When i rehot M2800 touch works for a few minutes.

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I don’t really understand why you reballed and replaced Homer and M2800 as they have nothing to do with TouchID. Homer is involved with the Taptic engine and M2800 are just coils for the backlight, Arc driver, Tigris and SpeakerAmp. As for U4805, it is a switch so it is possible that you reading an open circuit was due to this switch being open.

Is the problem with TouchID, as in it won’t recognize the fingerprint reader or is it a laggy button or erratic operation? Those symptoms can be caused by the Audio IC. If the audio problems are resolved, then you have a separate issue but there isn’t much you can do to fix TouchID.

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Minho sorry, i have probem with touch on lcd not with touch id (fingerprint).

Homer i reballed because in another forum one member counseled me. [br]

M2800 are only 5 coils, i know, but when i heat this chip touch work for few minutes.[br]

I measured open line on homebutton because there was damaged one resistor. So i measure and found connector pin on motherboard, it is 5 pin on homebutton connector and line name is I2C_MESA_TURTLE_SCL_CONN . So there is U4805 on the way, this is a reason why i try replace U4805.

von

I found when i heat whole board touch work. When touch does not work there is missing PP1V8_TOUCH and PP5V1_TOUCH_VDDH and AP_TO_TOUCH_MAMBA_RESET_L.

When i heat whole board this voltages are present.

von

There is no Touch circuitry on the iPhone 7 logic board, it's all on the screen. Other than the voltages, nothing else occurs on the board. I would try another replacement screen and if that doesn't work, check Chestnut rails.

von

Heating the whole logic board is a very risky thing to do. Many IC's are underfilled and "reflowing" is generally a bad idea. If you are missing voltages, then that's what you need to investigate. Have you tried a replacement screen?

von

Hmm, There IS circuitry for touch on iPhone 7--there a a few lines that regulate touch from the CPU to the connector if I recall correctly.

von

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My answer is “Stop following plz bro advice” on forums without thinking if it makes sense for YOUR problem.

You had a phone that had touch issues. So where should you start?

Look at the schematic and try to figure out what lines are responsible for touch on the iPhone 7—-what is touch power and touch data? Then measure with a multimeter to try and find a fault. Once you find a fault then think about how it could come to be like that and come up with a strategy to address the fault.

What did YOU do to troubleshoot touch.

You replaced HOMER—-which has absolutely nothing to do with touch and couldn’t possibly have been the problem.

You replaced trinity—-which has absolutely nothing to do with touch and couldn’t possibly have been the problem.

You did troubleshooting of fingerprint sensor which also has nothing to do with touch and is irrelevant in a phone that has no touch.

Everything you do to a device MUST be eliminating variables and simplifying the problem. What you are doing is adding to the problem with all this pointless work. We have no idea what effect all this heat on the board has done.

You have made the problem too complex to work on.

Troubleshoot touch with known good screen that works on another device. Troubleshoot the connector itself to make sure it can seat the screen perfectly. Troubleshoot the data lines for touch at the connector—-this is where most problems would be for iPhone 7 no touch. I know that you said that all resistance is okay, but that is almost certainly not true. You must compare to a known good, not zxwtool. If heat brings back touch, then something has too high resistance without heat—-find that line.

Verify that your touch voltages are appearing at the screen. Rather than use heat to try and make touch work, you can try pressure to see where is your open line.

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Tomas wird auf ewig dankbar sein.
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