Synthezisers & retro computing
Revival of a 365E floppy drive unit - Part 1
About 2 year ago while i was trying to replace the belt on the Thinkpad 365E slim floppy unit (IBM calls them FRU 41H8387/41H7444 depending on if they are internal or external in a case) i unfortunately snapped one of the read-heads off (due to temporary "sausage fingers" :) ). I immediately started to search for the various FRUs given by this page:
ThinkWiki floppy connector guide
but failed miserably to source a replacement unit (they are rarer than hens teeth).
Fast forward to the current time and i took a closer look on the drive and i noticed the Mitsumi stamp on it - the unit is actually manufactured by Mitsumi and (in the IBM shroud) the model is called "D353FE2". Googling for that comes up with nothing, but lo and behold, apparently Mitsumi has a model just called "D353F2" (googling for this will give quite many hits).
What the Mitsumi original unit looks like:
And here is what the IBM branded unit looks like:
Naturally, IBM did not seem to just use a bog standard Mitsumi unit because in the IBM branded version, the connector is of the protruding kind with pins (which then "snapped" to the laptop) while the standard unit has this flat-cable connector.
Internally, the connector is stuck to this small control-board and i suspected that it might be worthwhile to source a standard Mitsumi D353F2 unit and then swap these boards between them? Would it work? What did i have to loose (you guessed right. Nothing :))
So i got to work, effectively swapping out the guts of the Mitsumi unit, putting the IBM unit contents in there
PCB with Protruding connector is IBM, the other is Mitsumi.
and i tried it out. No dice. I could hear the drive ticking inside the machine, but it surely was not reading any disks. Time for step two - the drive belt.
I measured the old belt using my digital caliper and found that it was 1.45mm wide, 0.48mm thick and ~22.4cm long. Taking into account that it most probably had stretched during its life (and dried out quite a bit), i assumed that the correct specs would be:
1.5mm wide, 0.5mm thick and 22cm length
and so i found a nice shop on Ebay who had one that could fit according to the potential measurements (sold as new for a Matsushita EME-279TC unit). I got the small package home and took the drive apart again, mounting the new belt. Time for the grand finale. Would it work? I grabbed one of my floppies off the shelf and tried to format it - it gave me a message that track 0 was bad. Bummer. I then used an unused floppy and retried it and this time it actually formatted the whole thing properly. YES!!
Now i was able to create files and reading them back worked. One odd thing that i noticed was that the newly formatted floppy reported back 1,1MB available (where it should really be closer to 1,4). I then took this same floppy and used it on another machine and to my dismay i saw that the new machine could not actually see my newly created text-file (from the 365E). Bummer again. I then wrote another textfile to the floppy and tried to read it on the 365E but the machine could only see the actual file that itself created in the first step. This probably means that the read-heads are out of alignment...
But those trials and tribulations will probably be in the next post here ;)
Posted at 11:13PM Dec 03, 2021 by my03 in Technology | Comments [0]