... or fixing several 1541 drives for fun ;)
1541 fixing chaos
Part of you already knows that some time ago I've bought quite a few computers,
but I didn't mention that 15 Commodore 1541 floppy drives came along with this lot.
Only one of whole 15 units was working without a problem, which quickly resulted in a total disassembly mess :D
Apart from above, I've also diagnosed quite a few faulty chips. Few fried VIA chips, some 6502 and in one particular unit, an electric motor controller plus a 74LS14 was fried. Nothing really new, common issues and fixes that are really well documented in da Internetz, so I'll skip the full description of 'em.
With all cases and mainboards fixed, clean and ready, fixing drives was the only thing that was left to be done.
I've encountered a couple of interesting issues here.
There was one drive that was extra noisy and I couldn't figure out what was causing this noise.
After a bit of deeper looking, I've found a problem.
It was a slightly dirty floppy holder wheel.
Cleaning and lubricating it sorted an issue.
There was also a problem with a loud floppy motor in another unit, but that was sorted out by simply injecting a tiny drop of silicon-based lubricant into bearings.
Testing and further fixes
I must say that ALPS(brown) drives are damn indestructible if compared to MITSUMI.
All ALPS drives worked without a problem after cleaning and tweaking. On the other side, there is MITSUMI, only one out of seven units was working. I was curious how that is possible so further testing was needed but let's see what was done to all working drives first.
To test the drives, I've used a cartridge image from an excellent website www.worldofjani.com
I've flashed it to an EasyFlash3 and I was ready to go ;)
Ok, back to MITSUMI drives problem. These drives didn't pass any test. It looked like there is a reading problem. After a bit of Internet browsing, I've found that fried coil in a head might be the cause.
1541 drive head has two coils inside - one for reading and writing and another for erasing.
Turns out that simple multimeter resistance measurement can reveal if coil is fried or not.
It also turned out that all MITSUMI drives that I have, has at least one of two head coils dead. I've decided that I'll take a deeper look at it.
Here are some pics.
Coils are sealed in some sort of silicone compound
I've managed to gently remove this silicone gooey and have a closer look inside with my USB cam.
I was hoping that maybe something else is a problem, not the winding itself. I've checked for continuity and unfortunately, it turned out that in all heads one of the windings is fried.
I am currently trying to figure out how to repair or replace these broken heads so no h4x here yet. Sorry ;)