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iphone 6 plus fails to complete boot sequence

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  • iphone 6 plus fails to complete boot sequence

    Previously this phone powered up fine. Only issue was intermittent touch loss.
    (Looked like?)Flat battery only so put the phone (semi disassembled - had the Top plate that covers the display connectors off and the battery plate) onto the charger.
    Was drawing 900mA. Decided to relocate to another charger. As soon as I plugged it in the screen flashed for a split second. Current draw went quickly to 250mA. Stayed there. So I unplugged. Back to the first charger current draw is as before ie 900mA.
    Disconnect USB. Plug battery connector directly to DC power supply. 0mA before prompt to boot. Power up. Screen lights up with Apple Logo for a fraction of a second then dead, current draw climbs in increments up to 240 -270mA and stays there for 10-30 seconds. Then drops to 0mA. Disconnect from DC Power Supply. Remove the screen. Reconnect to DC Power Supply. Now climbs to 90mA for about 10s and drops to 0mA. Press the power button - repeats. Attached is a picture of semi disassembled state of phone when this happened. Took the screen off and tested on another iphone 6 plus. Phone booted fine and the screen works A OK. So, regarding the intermittent touch loss motherboard, I suspect I've got a short on a display related power rail that's killing the boot sequence… but I'm only guessing. I think the next move is to locate all the display related power rails and start looking for a short? Seated resistance mode? Hunting down shorted caps? Is this a reasonable strategy?
    Attached Files

  • #2
    Any iPhone 6 plus with intermittent touch is touch disease. Heck, any 6 plus that doesn't have any symptoms is still touch disease, it's a massive epidemic.

    You have two unrelated problems---a phone with a complaint of touch disease, which is such a glaring signature problem that there is no need for any further diagnosis---remove meson, add the M1 jumper, reball and put it back on to solve.

    The second problem is the phone has developed a CPU data line problem while in your hands. How did this happen? I don't know.
    Troubleshoot this second problem first before you worry about touch disease--they will be unrelated.

    HOW did it come to be this way?
    A-This phone has a prior microsoldering repair attempt that somehow made it susceptible to develop CPU output open/bridged line. Maybe a solder ball under backlight driver or a nudged i2c resistor. Maybe a shield soldered back on and touching something. Start with a full microscope examination.

    B--This phone was working, connected to a charger, now not working. It could be charger damage, which would affect tristar. You could change tristar to rule it out.

    In any case, your next step is rule number one. You don't have a board problem until you know you don't have a parts problem. Work with the board out of the frame by itself, with only a KNOWN GOOD (not new, a known good that has recently been proofed with another phone) charge port, and DC power, nothing else. After that, full microscope exam of the board and report your findings.

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