Otrona Attache: The adventure continues

Date: Thu, 2 Oct 2008 00:55:26 -0700 From: derschjo at msu.edu To: Subject: Otrona Attache: The adventure continues Thanks to TonyM, I have a replacement power supply that works and I now have the Otrona mostly running. (I do intend to repair the original power supply -- I found what looks to be a bad transistor and I've ordered a replacement (can't find it at the local shop.)). The Otrona almost works properly, it just won't boot from floppy. I need a bit of help debugging the floppy controller. Thus far I've verified that the following are good: - The drives themselves and the disks I'm trying to boot from (hooked the drives up to my PC and used ImageDisk to dump the disk contents successfully) - The drive cable - The NEC 765 controller (was originally bad! replaced with a known-good 765 from an old PC floppy controller and this improved things somewhat.) Symptoms are: Drive spins up, seeks to track 0 but won't boot; running the ROM diagnostics (thanks to Bob for a scan of the service manual!) helps narrow down things a bit: - The "Format" diagnostic runs, which means the heads load, the drive seeks, and enough is working so that the Otrona thinks it's formatting. I've tried reading the resultant diskette using ImageDisk and it chokes on it, so I'm not sure it's formatting correctly. - Reading or Writing a sector on a known good, CP/M formatted floppy fails. The error code returned (4004) indicates a missing Sector ID. There aren't a lot of chips involved in the floppy controller (about 12 or 13) so I'm hoping this shouldn't be too hard to track down. Any suggestions on where to start? (Schematic at http://oldcomputers.net/Attache_Schematics.pdf on page 6). Would it make sense to start investigating the chips leading back from the /RD DATA pin? Thanks as always, Josh