The necessary "gear" for large array BGAs (including 256 pin) is a oven and an X-ray machine. No, not your kitchen oven... You must be able to control the ramp rate of the temperature and ensure it peaks at a particular temp for a specific amount of time. These parameters depend on the device(s) installed. If you want to ensure the solder joints are good (no cold solder joints, etc.) visual inspection is virtually impossible, you must x-ray the populated PCB. This would be quite a job for the DIY to complete with any degree of reliability. Our local assembly houses will remove, reball, and replace a BGA for around $200 (incl. x-ray) so I assume it would be even cheaper for installation only. Beyond that, the new BGA would likely require a new multi-layer PCB layout; and multilayer fabrication is much more expensive than 2 layer (simple double sided).

That's the beauty of the empeg, it's a true custom open source computer in your dash. When I show this to the other engineers at the office (especially the guts of it) they all respond - WOW, and these guys are DIY types. We should consider ourselves priviledged to own one (or more ).
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MK2a 160GB

11 Years later, these Mk2a units still rock...