TRS-80 "Eight Meg Disk System" questions...

Thanks for all the responses to my questions regarding my problem -- I think I understand the situation a bit better now; just to make sure, since the terminology (mostly around "controllers" vs. "interface boards," etc...) seems to be used somewhat loosely, I'll attempt to sum up the discussion so that I can eliminate any confusion on my behalf... So... a complete Model II/16/6000/etc. hard drive setup (for the 8mb, 8" drive -- I'm ignoring other potential configurations at the moment) would consist of the following hardware: 1. The proper host interface board (this is the card that goes in the Model II/16/etc. cardcage) 2. The actual hard drive controller (which lives in the primary hard drive enclosure) 3. One or more SA1004 8" hard drives (in primary/secondary enclosures) What I have at the moment is 1 & 3; since my drive is a secondary drive I lack #2. (And I did double check, to make sure -- my enclosure contains the drive and a power supply, but no controller board.) From the responses I've received I get the impression it's possible to substitute a hard drive controller for a 5mb TRS-80 hard drive for #2 -- I do happen to have one of these (I have a Model 4 external 5mb drive with a broken drive)... if it is possible to do this, can anyone provide details on how it's done? Thanks once again, Josh