Can you find out what's driving the diagnostic LEDs that are mentioned in the Servicehandbuch? Maybe that could tell you more.
I found the disks of the Test and Diagnostics System that is mentioned in the Servicehandbuch. I hadn't mentioned them before because they wouldn't boot, and I thought they'd be corrupted. Tonight the TDS came up fine, so I'm posting them here.https://dl.dropboxusercontent.com/u/55419307/Siemens%20PC-D/PC-D%20TDS.zip
They are in a different format than regular PC-D disks.
It's always exciting to see additions to the PC-D driver mentioned in the SVN history - thanks folks!