Got to have a go at the removal of the eMMC chip and so far successful. WIth some hot air the chip came away nice and cleanly.  I had a few practice goes with the RAM chips and got the technique nailed by the time I did the eMMC chip.

Prior to me getting my hands on it my brother had sent it to a "profesional" data recover service but they couldnt extract the data as they suggested something like what ever caused the unit to fail in the first place was preventing them accessing the eMMC. When I get my hands on a PCB I pliek checking out what chips are on the board and look up their specs and just for my own entertainment. And this board was no different. there was the usual RAM chips and GPS module from uBlox then i uncovered a large device with a small burn hole in the face of it. The IT8528e is a power maagement IC and having a big hole in it isnt going to help anything. Punch IT8528 into duck duck go and the first thing that comes up is 

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https://www.aonemobiles.com.au › product › ite-it8528vg-fxo-power-management-ic-surface-pro-4

ITE IT8528VG FXO Power Management IC (Surface Pro 4)

Description. This is a replacement ITE IT8528VG FXO Power Management IC for the Surface Pro 4. This PMIC can fail leading to a common 3.3V rail being pulled low/shorted.

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Well I reckon that would be the problem - a $14 PMIC would have brought the trimble to a halt and prevented an in circuit data recovery - I suspect if that was replaced in the first instance my brother wuld still have a working trimble with all his data intact..