Sleep/Wake Button Not Working

Dear all

I have a problem with using a sleep/wake button because it does not work.

It has been worked as normal but one day this problem suddenly took place. Although I have replaced the flex cable but it does not help to fix this problem. I have not found any problems on the connector linking to this flex cable.

Another weird issue related to this problem is that it tries to boot itself after I turn it off using the assistive touch. However, the phone just shows Apple logo on and off and is not able to actually boot unless I plug in the usb cable.

(In this regard, I guess this has some issues related to power management IC)

As long as plugging to the usb cable, it boots up properly.

Without these issues, this phones is in full working order.

Please advise me to figure out these problems

many thanks in advance