iPhone 6s - Power / volume / silent button flex cable replacement

Hi all,

I recently started my first iphone 6s (UK) repair but have hit a brick wall and was hoping someone more knowledgeable on here could help me?

I had to remove the mainboard to replace the entire flex cable as the silent button was no longer working - to my surprise i think i have completed the job about 90% as the after i replaced everything i managed to get the phone working again.

Although i still have a couple of problems i can only switch the phone on by plugging the charging cable into the phone - for some reason the power button won't work either will the volume up and down buttons but strangely the silent button does work. I order another flex cable as i though the one i purchased 1st maybe faultly but i have the same issues with the new cable. To test the new cable i didnt completely remove the mainboard again i just unplugged the 1st flex cable and plugged the new one in to test it.

Does anyone have any experience of a similar problem - could it be an earthing issue? or something else?

Any advice would be much appreciated.

Kind regards Nuub