If you are able to boot DOS on this system (has to be real DOS, not a DOS
prompt from another OS).
I suggest you use my "ImageDisk" - it has very good test/analyze function
where it can give the drive a good test and report on lots of things.
(If the problem turns out to be the old "dirTy heads" thing, ImageDisk also
has a "clean heads" function where (with some cleaning solution - or at least
some alchol - it will "scrub" the heads back-and-forth, much more effective
that "doing dir to make it spin.").
ImageDisk has to run under pure DOS because it access the floppy controller
directly and in traditionally non-standard ways. (ImageDisks primary purpose
is to archive/restore "vintage computer" media - that means ANY format the
the PC FDC can physically read/write - not just DOS/MicroSoft formats - I
even use it for old 8" systems - I give information of making an adapter on
the site).
For this reason, ImageDIsk does not "go through BIOS" or make use of BIOS
floppy-drive configuration (my ImageDisk system does not even have the floppy
configured in BIOS).
Best place to get it is: "Daves Old Computers" -> "Download Software/Images"
(near the bottom).
Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal
- Dave ; https://dunfield.themindfactory.com ; "Daves Old Computers" ; SW dev addict best known:
ImageDisk: rd/wr ANY floppy PChardware can ; Micro-C: compiler for DOS+ManySmallCPU ; DDLINK: simple/small FileTrans(w/o netSW)via Lan/Lpt/Serial