Sunday, September 13, 2015

Commodore 8296D: De-Deutsch-ification

Some years ago I picked up a Commodore 8296-D from a kind fellow aus Deutschland (from Germany).

If you don't know about the C= 8296-D, it is a computer similar to a CBM 8096-SK, but with built in CBM 8250-compatible dual disk drives and the Execudesk rom and software package.  The 8096-SK, if you don't know, is the new-"Porsche" style of the CBM 8096 computer.  And the CBM 8096, in turn, is a CBM 8032 with 64k expansion.  The 8032 is the 80 column version of the Commodore PET 4032-12.  If you don't know what the PET 4032 is, shame on you.

Since I loved the 8296 so much, it quickly became a member of my official PETting Zoo.
Several reasons eventually put it on my workbench.  One is to "re-cap" the Matsushita drive mechanisms.  They are notorious for leaking capacitors, and that notoriety is well-known to this collection.  Every Matsushita drive I have inspected has had at least one leaking capacitor.

Another task was to fix the internal roms.  The computer had been born in Germany as an english 50hz 220V Execudesk computer, but at some point had been converted to a German 8096-SK-D by replacing the Execudesk rom with a German editor rom, and the addition of a Paperclip-software chip, both on hand-written 462532 EPROMs.

The last task had to do with the internal fan on its magical power supply.  For some reason I cannot explain, the power supply works perfectly at U.S. 110V.  Nice for me!  However, the fan only operated at 220V.  A simple fix.

The first task was to recap the drives.  These would be the 5th and 6th such drives I've done.  This wasn't exactly a "new" task, and yet on the second of the two, I had a hell of a time with two of the screws on the magnetic platter. In fact, these were the first unturnable screws I'd ever encountered.   After researching the problem on the internet and trying several things, I had only made the problem much worse.

The last thing I wanted to do was take a drill to them in order to use a stripped screw remover, but that is exactly what it took.  Luckily only one of these drives suffered this fate, and I'll know more to avoid it in the future.

The second task was the ROM replacement.  Unfortunately, I had no spare 2532 ROMs.  So I ordered some compatibles off eBay, and received TMS 2532As, which I discovered, to my great annoyance, are unprogrammable by either my Prominade C1, the parallel port-based programmer on my PC 50-II, or my modern PC's USB-based programmer.  In frustration, I ended up re-purposing the Paperclip rom (I had others).  I burnt the english Execudesk rom, same as the one on my U.S. CBM 8296 computer, and plugged it in.

To my surprise, this didn't work.  The Execudesk menu was shifted too far to the left.  While that was only a mild annoyance on that particular menu, a similar problem made BASIC unusable.  I had discovered that there truly is a difference between 50hz and 60hz PET editor roms, and what I needed was a 50hz Execudesk.  Some research uncovered the fact that my U.S. Execudesk ROM was identical to the PET Editor 4.0 60hz rom, with the addition of the menu code at the end.  So all I did to generate a 50hz version was to add the Execudesk code to the end of the PET Editor 4.0 50hz rom.  In the end, I got my PET Editor 4.0 50hz Execudesk rom, and the computer was in business.

The last task was the simplest.  Find a 3 x 3 x 1.5 inch 110V fan, and swap.  Easy-Peasy.

The PETting Zoo is whole again!

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