TRS-80 Model 12 crt substitution - Now I need help with 8" drives

Thanks to all who replied to the crt problem. The crt from the TRS-80 Model 4 was a perfect replacement for the Model 12. Now I have 2 - 8" Tandon thinline TM848E dsdd drives that have problems (in the Model 12). Drive 0 (lets call it A) used to work fine but now all it does is blink (the red busy led). 3 blinks followed by 1 blink or maybe it's 1 blink followed by 3 blinks, hard to tell. Drive 1 (call it B) always made noise and wasn't as reliable as A. I took A out, made B drive 0 and installed the resistor pack. Now B won't boot, I get to "initializing" and then I get a seek error. I have an original TRSDOS 2.0b disk and a copy and both used to work. Both get the same error. The drives have what I am going to call a logic board that's easy to remove. It has the drive and power connectors on it. I've tried every combination of mixing drives and logic boards but I still get the same errors. Does this blinking make sense to anyone and can I cure the seek errors on the other drive? Thanks again for listening to my ranting. Ralph