moved TM drive from local machine to another machine on network, TM creates brand new archive for same machine

[Kevin Callahan]

I moved my TM backup drive from my MBPro to an iMac on the same  
network.  I launched TM and told it to use the remote drive (mounted  
via sharing off iMac).
TM is now creating an entirely new backup file.  Is there a way to  
point to the existing backup?  I don't see any prefs allowing me to  
point to the archive I'd like to continue using.

Kevin