Tandon TM502/Tandy 2000 problems

All: I?ve been working for a while on resurrecting the hard drive system of my Tandy 2000. The short story is that I have two systems with TM502 hard drives, both of which failed after a few uses (both were donations to me earlier in the year) and were no longer recognized by the system. Running the format program from Tandy DOS (MSDOS 2.21) fails to recognize the drives. I jacked one into a MFM controller on an older PC, re-ran the low-level format and formatted it with DOS 6.22. I then verified that it booted. I moved it to the T2k, where it was not recognized again, but this time, I was able to run the formatting program and now it?s usable from DOS 2.21. So, the hardware is good and I guess running the low-level formatting program from the ROM (g=c800:5) reinvigorated the drive. Since it seems that the low-level formatting has gone south on these drives, is there a non-destructive low level formatting program that?s good for this? I vaguely remember Spinrite, but I no longer have a copy in my box-o?-disks. I don?t want to destructively format the second hard drive since it has lots of programs on it from the person that sent it to me and I?d like to recover them if possible. I even wonder if the remaining drive can be resurrected at this point with the data intact. Oh, for those interested, the Tandy controller happily uses an ST-225 (20.1mb) drive as an alternate. Thanks for any info. Rich -- Rich Cini Collector of Classic Computers Build Master and lead engineer, Altair32 Emulator http://www.altair32.com http://highgate.comm.sfu.ca/~rcini/classiccmp .