Compaq Portable II fails to boot - some analysis

Tom Gardner thomas.gardner at
Thu Jan 28 13:11:41 CST 2010

Sometime ago I posted a request for help on my two Compaq Portable IIs that
failed to boot from the FDD.

I now can boot one using an "off the shelf" (at Weird Stuff) half height 360
kB FDD in place of either of the two Canon 5201 1/3 height FDDs that were in
the two Portable IIs.  Both exhibit the same failure mode, while trying to
read the disk visibly spins erratically, as if there were some form of
stiction causing it to go slower and then faster.  Manually turning it with
and without a disk, the spindle motor feels free of stiction.

It is surprising to me to find both Canon 1/3 height FDDs fail in the same
mode, suggesting a fundamental flaw in the design.  For example, the full
height and half heights I used in this project are older than the Canon's,
of unknown provenance, but all 5 have worked flawlessly.  Any ideas, other
than avoid old Canon 1/3 height FDs?

Anyone have a working 1/3 height 360 kB Canon FD?  (I think I need Canon to
get the bezel right on the machine I am "restoring").


PS:  I bought a package of 20 360 kB FDs off the internet and one of my
problems was that about 1/2 of them were full of defects, causing some of my
problems.  I finally solved that problem by throwing away any disk with any
defect found during Format and doing a Diskcomp after each Diskcopy.

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