Deunan wrote on 2021-07-22, 13:02:
I never had to do a repair like this but I remember reading about this issue. I have some "suspect" second-hand floppies but they don't seem to be progressing into worse state, I do wonder if maybe some heads work better then others - due to shape maybe? Keeping them clean helps as well. Also there was a mention of unusual noise when floppy surface is peeling off and accumulating on the head - never witnessed that either. I have one noisy floppy but it looks fine, seems to be a problem of the envelope, not media.
I use a scope+IMD combo to align heads, first with old floppies that I won't miss much if they get damaged and when that works well I switch to original software - the assumption here is these floppies were written with near-perfect aligment so are good templates.
BTW I wanted to ask, did you install MASM to use it or just for the editor? I switched to NASM but the DOS version requires 386+ CPU (and it better be a fast one). Most often then not it's easier and faster to develop DOS apps in VM or using DosBox and only doing the low-level HW testing (and benchmarking) on actual DOS PC.
I installed MASM 5.1 because I found a copy of it locally and I find it fun developing little bits of software on the host computer. Similar to using TMP on Commodore 64 or ASMOne on my Amiga 500.
I ended up getting the M editor (from the Editor install disk in the MASM 5.1 package) installed on the XT using a disk image and some imaging software to make a new disk. It seems to not be great in MDA mode, and I've just ended up using the MSDOS 5 EDIT program so far instead. The "Hello World" I typed in using EDIT compiled and linked just fine using MASM so I might just keep using that.
As for the disk drive, it's an original full-height IBM branded Tandon drive and they aren't easy to come by in Australia. I don't really have any other 5.25" drives I can drop in so it was 100% worth it to me to repair the drive. I'm having to regularly tinker with it to keep it aligned. I've got one of the half-height YE Data drives coming in from overseas with the plan of using the blank half-height bay for a 720k drive if I can find one of the original blue-button 720k drives IBM optionally shipped with the XT and XT286, similar to the AT and PC Portable 3.5" drives but with a textured black bezel for the XT and XT286. If this happens i'll take out the Tandon drive and use it for spares if I ever manage to get a 5150 for a decent price.
I'm not pulling the drive apart any time soon, but attached is an image of the head after an attempt to solder it back in place. This isn't how it looked in the end, as I ended up adding a very small piece of stripped magnet wire to the joint to sure it up and had to spend a few hours over several attempts getting the head Azimuth in the right ball park.