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Model 4 upper drive problem


Dec 23, 2021
Ok, this is strange.

I ran the disk check, and the program didn’t report anything wrong with the drive. So I quit to TRSDOS, put a blank in the upper drive and attempted to format it- it worked with 0 bad sectors!

Then I tried putting my original boot disk back in, and it went back to its bad behavior once again. I’ve never seen a system disk cause issues with hardware like this before, how is this even possible since the boot disk works?


Veteran Member
Mar 14, 2013
Chaffee, MO
It sounds like a problem with the Hinge part that isn't clamping the media enough to spin the
floppy, or the Head pad that loading against the floppy on the back side opposite the Read/Write Head.

I'd start by looking in that area. The Document I send had Photo's of how much the center hub has to
tension the assembly. It isn't much.


Patrick.B (TTR)

Experienced Member
May 11, 2011
Houston, Texas, USA
okay do this., boot in drive 0 then blank in 1, since it formats properly use, "backup" in TRSDOS and set master as 0 and destination as 1, if all goes well then goto 1, else what errors goto 3
1 attempt a Dir of drive 1 (DIR :1) if that works well then goto 2 else if then could be a read head process issue.
2 take the backed up floppy in drive 1 and put it in drive 0, press red button to reset the machine if machines boots then goto 3, else if no boot then likely your drive 1 needs to be aligned.
3) the mystery continues.