Originally Posted by gitit20
To many control and interface parts are not installed on to the main board so even if you solder a plug or socket for the data card it won't have power and no hard interface for it to function...
you can see on top where all the blank pads are the is for the Verizon models where the evdo radio would be and its control and so on.
only way I see this working is to connect an external card via the USB sorry to be a buz kill but its the plain truth I have been working on phones and computers most of my life and am a cellular tower tech.
I can't go in to details but in the next 3 to 5 years cellular tech will be much better then now we are talking 200 plus megs a sec down (with out any speed caps placed by the providers)
I found some higher resolution photos of the 3G Xoom's motherboard at http://nifaq.pbworks.com/f/129884949...therboard.jpeg
, which have enough detail to show the markings on the chips.
It looks like the WiFi Xoom is missing the baseband radio on the top left, as well as the regulator for possibly the radio/PCIE slot on the middle left, plus the PCIE interface as previously mentioned. The regulator is a switching step-down made by TI, part TPS54331. That part looks decently solderable, but some of the discretes nearby look to be 0402's or smaller, which is very difficult to solder by hand with specialized equipment. Same thing for the baseband on top, which is a Qualcomm MDM6600 with a Hynix H8BCS0QG0MMR-46M memory chip, plus some small unidentified IC's, including an Avago A2FI042. Unfortunately, I doubt those parts are even available in small quantities, plus they look to be LGA or BGA package, which would need a reflow station at minimum to properly solder. Plus you're still missing the metal shielding cans that are supposed to cover both areas for FCC certification.
I'd guess that the SIM card slot is electrically connected to the PCIE slot, because I doubt Motorola would have two separate board designs for the 3G Xoom and WiFi Xoom, due to cost since this looks to be a 4+ layer board.
Maybe if you can salvage a cheap 3G Xoom motherboard, you could cobble together a working 3G Xoom, but it's very unlikely that you would be able to obtain the necessary components to directly mod the WiFi Xoom into a 3G Xoom using the original parts.