Chosen Solution
Hi, I have accumulated quite a few iphones 7/7+ which i could not start due to message Unable to Activate Shutdown. Initially I thought it could be BB_CPU problem but usually it happens after attempted Audio IC job and the phone still boot but does not show IMEI/Modem Firmware. In that case I just re-ball BB_CPU. But the phones at hand with this error message have not been opened before so I am confused. perhaps more experienced micro solderers could shed some light? Thanks.
This sounds like a Qualcomm model. The baseband power management chip has a voltage regulator inside. I think it becomes shorted sending VDD_main voltage into the baseband chip that is why apple had a recall on that model. You could replace the baseband power management chip but the damage has already been done to the baseband ic.
