Logic Board Replaced - Time Machine doesn't recognize old backup!

[pprior]

Had to have the logic board in my Mac Pro replaced due to faulty audio input jack.

Time machine backs up to an external drive (DROBO array).

When I brought the machine back home, time machine does not recognize the old backup (last backup never) and doesn't have room to backup a new system because the old TM files take up most of the drivespace.

Is there a way to "force" time machine to accept an old TM backup file? I don't want to delete everything and start again. I assume this is because the logic board (motherboard) was replaced.

Note that the system drive and all internal hard drives were not modified, and the OS was not reinstalled or anything like that.

One other item: the tech forgot to run some software at apple and my machine currently has no serial number (about this mac...) assigned. They are sending out a tech to fix this - does time machine back up based on serial number? If so, maybe that will fix the problem.

thanks for any help!

 

[Amdahl]

Time Machine uses the Ethernet adapter MAC/serial address as an ID. If you have a new logic board, you have a new MAC address.

This link describes what to do:
http://www.macosxhints.com/article.php?story=20080128003716101

Be sure to note the correction in comment "Minor correction (escape the spaces)", or you might have trouble.

Looks like this one also might be key: "By: tnmacguy on Fri, Apr 4 2008 at 8:35PM PDT."

Basically, it sounds like a pretty tricky situation.

 

[pprior]

Wow, thanks SO much that sounds like exactly what I need. I'll try and run through this later when I have a bit of time and will report back if I'm successful.

Again I really appreciate this help - I never could have possibly figured that out by myself!

 

[pprior]

Too many problems posted with inability to go back to old backups.

I ended up reformatting and starting from scratch with my backup disk.

Apple really should make this work better.

thanks again anyway, I do appreciate the effort!