Arkanix wrote on 2021-07-22, 07:01:
Managed to get it fixed up. One side of the bracket that holds the top head had snapped, so the head had to be soldered back onto its mount. It had to be soldered at JUST the right angle otherwise it'd read the outer tracks but fail to read the inner tracks due to the smaller radius of the tracks closer to the centre.
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.