retrohax.net

… or fixing several 1541 drives for fun 😉

[Intro]

A challenge!

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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 the whole 15 units was working without a problem, which quickly resulted in a total disassembly mess 😀

Cases were first to go.

It took a while but finally, I’ve restored ’em.
…except one just for comparison 😉



One of the cases was badly injured 😉 I had to sort it out too.

De-dusting with an air compressor was kinda mandatory.
Here is an absolute winner of a “Grow your dust” compo 😀







Other competitors were quite dirty too 😉

In the meantime, I’ve started working on electronics.

You can’t spot a problem here, can you? 😀

Apart from the above, I’ve also diagnosed quite a few faulty chips. A few fried VIA chips, some 6502, and in one particular unit, an electric motor controller plus a 74LS14 was fried. Nothing new, common issues and fixes that are well documented in da Internetz, so I’ll skip the full description of ’em.

Next, I had to clean all the motherboards.
The winner could be only one … codename: the hairy 1541 🙂

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 extra noisy drive 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 were 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 😉

All the drives had the speed set to 300 RPM as close as possible.



I’ve also corrected a head alignment in all working drives.

MITSUMI drives

Ok, back to MITSUMI drives the problem. These drives didn’t pass any tests. It looked like there is a reading problem. After a bit of Internet browsing, I’ve found that a 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 a simple multimeter resistance measurement can reveal if the coil is fried or not.



It also turned out that all MITSUMI drives that I have, have 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.

Here is how the first coil looks.

and a second coil is here.

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 😉

An outcome

So here are all drives that I’ve managed to repair. All of ’em have ALPS drives because MITSUMI ones are waiting for the solution.

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