A friend had problems with his Duo 210 recently, and I thought a brief exposition of how we solved them might prove useful to Duo users and anyone who does trouble-shooting. Bill has a Duo 210 and a Duo Dock, although no monitor at the time. He could to print to his serial DeskWriter, but printing to a PostScript LaserWriter or to a PostScript file (with or without background printing on and from almost any application) caused his Duo to hang. However, when he printed from PageMaker using the Aldus driver, it worked fine. He tried the standard procedures, booting without extensions, replacing the LaserWriter driver, and even reformatting his drive (getting more space by repartitioning in the process) and reinstalling the System and his applications from scratch. Nothing worked. After he had an Apple Express Modem installed, his serial DeskWriter acted up as well, but we solved that by installing the DeskWriter 3.1 driver and fiddling with the many Control panels that control the port mapping.
Finally he brought his Duo, Dock, and DeskWriter over here so we could test on my network and use my 13" monitor with the Dock. Three problems arose quickly, and all the problems occurred whether or not the Duo was docked. First, the DeskWriter in AppleTalk mode hung halfway through printing if extensions were on. Second, when I tried to copy Conflict Catcher from my hard drive over the network to the Duo, I received failures with error #-37. Third, printing to my QMS-PS 410 PostScript laser printer caused a hang after the first "starting job" message.
Running Conflict Catcher in Conflict Test mode identified the elderly SNDPatch extension as the culprit for the DeskWriter printing problem. One down, and a win for Conflict Catcher since Bill had a slew of extensions that would have taken hours to test.
We then spent an hour trying to figure out why the Conflict Catcher files wouldn't copy, and eventually chalked it up to network daemons when we realized all other files copied fine. We finally ended up copying the Conflict Catcher files in an archive, and CopyDoubler author Dave Heller of Fifth Generation Systems told me several days later that the problem stemmed from the fact that those two filenames started with an ASCII 0 character to make them sort first. Apparently, an ASCII 0 character first in a filename confuses network copying to no end. On to the printing problem, which was the main one anyway.
Booting without extensions made no difference, and neither docking the Duo nor using the LaserWriter 7.2 driver was any more encouraging. Finally, we laboriously modified a copy of the Disk Tools disk so we could boot from floppy and print. You need a System, Finder, Duo Enabler, and Chooser in addition to LaserWriter, and there is barely enough disk space. When we booted from that disk, the QMS came to life and printed correctly. Replacing the System and the Finder with the versions on the floppy made no difference, so we copied the entire boot floppy's System Folder to the hard drive and blessed it in favor of the old System Folder. That worked, which isolated the problem to the old System Folder. We gradually moved folders over to the new System Folder (testing as we went) and it worked fine until we moved the Fonts folder (remember, this is a Duo, so 7.1 is necessary). Aha, a corrupted font! I hadn't thought to check Bill's fonts since I'm not used to System 7.1 and the System file hadn't been the problem, but it turned out that he had a herd (or maybe fonts come in gaggles or troops?) of public domain TrueType fonts.
At first we thought it might be related to the fact that he had some fonts loose and others in suitcases. Bill had heard that loose fonts can cause troubles, but packing his loose ones in a suitcase didn't help, and it ended up being a matter of testing each font, one at a time. Too bad Conflict Catcher doesn't help with fonts. Bill isolated the rogue font to be London, edging out the one we suspected on principle, Nixon in China.
The curious part is that we were easily sidetracked because of unrelated problems that seemed to point to AppleTalk and the LaserWriter driver. The fonts were also disguised by the fact that he had printed all them, including the corrupted one, via the serial driver for his DeskWriter. Yet, somehow the LaserWriter driver looked at all fonts, even those not used, and crashed when it hit the corrupted one.
There are three morals to the story. First, the Duo can be a mega-pain to troubleshoot if you don't have a floppy drive and an appropriate dock, although booting from a stripped RAM disk should have had the same effect and I'm still kicking myself for not having suggested that earlier. Second, corrupted fonts can cause seemingly unrelated problems, which I also should have considered, and if you don't do a clean install, those fonts exist in a new System as well. Third, in many trouble-shooting situations, booting from a clean system disk like Disk Tools can crack open a problem.
Incidentally, Tonya and I were talking about ways switching among multiple Systems, and we thought of a simple way of un-blessing (cursing?) a System Folder. In the System Folder, create a self-extracting archive of the Finder, and when you want to un-bless the System Folder, throw out the Finder. When you want to bless that System Folder again, expand the self-extracting archive (which will stick around for the next use), close the folder, and open it again so the active Finder realizes what you've done. It's generally a bad idea to have two potentially-active System Folders on the same disk, and this provides a low-tech way to switch systems without a switching utility.