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Jessa....a puzzle for you - iPhone 6 headphone detect

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  • Jessa....a puzzle for you - iPhone 6 headphone detect

    So here's a puzzle for you, so I get an iPhone 6 in today, it's showing headphones when none are put in.

    i try a new dock flex, no diff.

    i check the headphone detect line at the dock connector for shorts, none are found, I check the line in diode mode to two other boards, nothing weird is found.

    iv seen this issue on Ipads a few times and I found that changing the audio ic resolved the problem.

    so I changed out the audio ic....but the problem was still there.

    its only then that I saw one of the water damage stickers had gone off, but the board had no noticeable corrosion.

    i removed the lower shield to check the inline resistor on the headphone detect line and found that the speaker amplifier had been violated by the water and a few of the large caps around it. None of the headphone detect descrete components were affected.

    i looked at the schemetic for the speaker amplifier and saw that it had no headphone related lines on it. So thought I'd ultrasonic the board for shits and giggles.

    dry it off after clean and ipa and low and behold it now works ?!?

    What now ?, how the hell can ultrasonically cleaning the speaker amp have any effect on the headphone detect line when the headphone detect line has nothing to do with the speaker amplifier. Am I correct in thinking the audio ic acts as an amplifier for headphones ?, or is this somehow amplifier by the speaker amplifier too, which would make more sense to the problem.

    it doesn't show it on the iPhone 6 schemetic, but on the iPod touch 4th I think the headphone detect line used to connect to the positive headphone output and pull it up when the headphones were plugged in.

    i presume that's how it works on the 6, I tried to find a data sheet for the ic but could only find the generic version of the ic data sheet that didn't mention headphone detect.

    so the customers got a working phone back now, I'm just confused on how a bad speaker amp can affect a line it's not even connected to.

  • #2
    Who knows what types of interactions the audio ic, CPU and software must have in order to allow headphones to work. There are a bunch of lines that have headphone or HS in the title so if the system turns out to be complex instead of simple, my reaction is "yeah, okay" Sounds like system is complex, and we have no way to gain the information necessary to understand the system, so...its just complex.