I'm taking a look at the Roamio OTA board and haven't noticed anything yet, substantially different with the Base Roamio.
Could someone with a semi-recent Base Roamio, when you open the case for a HD upgrade or out of curiousity, post back the:
For comparison, the first batch of BB Roamio OTA's use:
P/N : SPCA-00095-000G
Here's some board scans for the interested:
Top of board 1
Top of board 2
Cable Card slot