I have an IBM 5162 that, aside from a failing ST-251 which I'm about to remove, works 100% perfectly. I've used it for many hours, tried lots of demanding software on it (timing-sensitive, custom hardware boards, etc.) and it runs everything perfectly...

...Except the actual 5170/5162 2.07 Diagnostics diskette. I've verified the disk, and a copy of it, read just fine on the 5162's floppy drive, but when I run it, I get strange combinations of characters that aren't printing out:


(in the screenshot, you can see 4 lines are mangled) Because I can't get the diags to work, I doubt I'll be able to test some of the option hardware I have installed that the diags supports... I can't even change the hard drive type (with this program). Again, I stress that the system works perfectly otherwise, it's just the diags that fail in this very odd way.

So, how does one diag the diag?