Troubleshooting an IBM 5155 - (portable personal computer)

From: Dave Dunfield <>
Date: Sat Jan 15 20:24:24 2005

>Other than that, any suggestions for figuring out if it is alignment, broken
>sensor, or something electrical?

IIRC, you mentioned that the other drive works, and you were able to boot DOS?

If so, setup the faulty drive as drive B:, boot DOS, and try formatting a blank
disk in the B: drive - if it works and you can read/write files to the drive,
the it is probably just a little out of alignment (You will probably find that
the disks it makes cannot be accessed on other drives).

Assuming this doesn't work, what error message does DOS give whwn trying to
access the drive? Also, normally the system will try much longer to access
the drive if it is seeing sector pulses - if it behaves pretty much the same
with the diskette in as with it out, then you may have an index sensor problem.

With power off, manually move the head out some distance from track-0 - does
it step back when the system starts - does it perform the "Seek test" at power-
up and does it look and sound exactly like the other drive? - if no to any of
these, perhaps there is a problem in stepping/track select, track-0 sensor.

Also, "scopes are your friend" - of you have one, take a look at what is
going on at the interface when you try and access the drive - you should see
the select line go low, look for index pulese, step pulses, track-0 detect, data
from the drive etc. - it might be fairly obvious what the problem is.

I assume you have already done this, but clean the head, and check all connectors
for even a little corrosion (edge, head, steppers etc.), especially if it has been
sitting around for a long time - same goes for config jumpers and option blocks
A good cleaning often does wonders!


dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools:
com             Collector of vintage computing equipment:
Received on Sat Jan 15 2005 - 20:24:24 GMT

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