I already tried as noted, but with zero luck. I got the case off, the drive is recogised via the BIOS and can feel what I think is spinning over. However, the Windows operation says the whole drive does not exist, and I cannot get to it via the DOS level either.
The smaller HD now has one file that used to be there, circa 2002, and have not used it in years.
Had some troubles with the posted diagram as of back when, for it did not match the underside of my drive exactly at that time.