Hi Tony and everyone, Thanks for the suggestions. All of the floppies that I substituted looked absolutely identical to the one that wasn't working. The last thing that I did was to try another floppy drive data cable (it's the standard PC-style dual floppy cable with the 34-pin IDC connector on the controller end and the card edge connector on the other end). When I simply replaced the original cable on the left-hand drive with the new one, the problem remained. When I swapped the cables to each drive (right going to left and left going to right), it worked perfectly! I assume that there must be some sort of drive select or other difference between the two floppy drives, but why the right one works in either location, and the left one works only as the primary (right-hand) drive is beyond me. After I convinced myself that everything was now okay, I physically interchanged the floppies (left to right and right to left) and took the opportunity to examine them very carefully to look for differences. I saw none. Even the date codes were identical! I'm not saying that there aren't any differences--in fact, there must be--but there wasn't anything obvious to me. The only difference with the 9836C that I notice now (besides the obvious lack of an error message at startup) is that the LED on the floppy controller board labeled "TR00" (those are zeroes) is no longer illuminated after the POST. I assume that is a Track 0 seek failure indicator, but I'm just speculating. Whatever the case, I'm delighted that it's fixed! Thanks to everyone for their help and suggestions! Regards, Stan From: ard(a)p850ug1.demon.co.uk (Tony Duell) Subject: Re: Problem with 9836C floppy drive To: cctalk(a)classiccmp.org Date: Fri, 24 Jan 2003 19:06:48 +0000 (GMT) Reply-To: cctalk(a)classiccmp.org low). I assume that's some kind of error code, which would be useful if the video side was malfunctioning. Anyone have a table of them? I assume you checked that the replacement drive was configured the same way (link settings, termination resistor pack) as the old one? What about the cables to this drive? Have you checked it's getting power (IIRC there's a conventional 4 pin power connector in there). Have you tested/swapped the data cable? -tony