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Unable to Activate Shutdown message (BB_CPU?)

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.

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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.

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It is actually Intel version. But nevertheless it is interesting theory. You might be right that at some point BB_PMIC was sending the VDD_MAIN voltage to BB_CPU and damaged it. So even if you replace the BB_PMIC the damage has been done to BB_CPU already.

I tried to re-ball BB_CPU but I am getting the same message/error. That supports your theory. I guess those devices go to 'No Fix' box.

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If it’s an Intel version I would take some diode readings around the BB_PMIC I would not declare it a no fix until you are sure it is not just the BB_PMIC which are easily replaceable

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