Floppy repair guides

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troed
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Floppy repair guides

Post by troed »

I'm going to [have to] start repairing at least two broken floppy drives, maybe four, in the somewhat near future. I've tried looking for guides for the different models used in Ataris but so far none of them cover the issue I have with one of them and I find it somewhat unclear what to do about the other. I'll happily write up a pretty guide with pictures myself, but I don't have enough understanding of electrical engineering to figure out possible causes and solutions by myself.

(I have six STs of various configurations and I'm now running low on working drives. I would really like to repair some rather than butchering working machines)

#1: 1040 STE, small button drive. Will add photos of PCB etc, but will start with describing the fault: Sometimes the motor simply doesn't spin up. It might also suddenly stop and start spinning as it pleases (immediately, binary, there's no rpm drop/rise). I've recently found that if it hasn't spun up a slight press of the eject button will kickstart it into action.

#2: Mega STE, small button drive. Just got this one, and it did read at least a boot sector once. After that it reported the wrong (too low) free space on a disk, and when I formatted a disk it said there was the same (and also too low, 4KB more than a single sided disk) bytes free. Curiously enough, that disk was actually correctly formatted and worked in another machine. After those tests all I'm now getting is the "krr krr" usually heard when trying to read unformatted disks no matter what I do. The drive does sound "tired" when it spins.

Most discussions of broken floppy drives I see center around "replacing the belt". I wouldn't immediately suspect the issues above to be caused by that though.

/Troed
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Re: Floppy repair guides

Post by Kubik »

#1 - looks like broken contact, wire or solder joint. One drive I have (Epson?) has the wires powering the motor PCB exposed on the side of the drive. When you slide the drive into it's place (it comes with some sort of cage that's screwed to the ST case, and the drive is just supposed to slide in), there's a good chance you'll cut some wires or at least damage them.

#2 - I'd try the diag cart, and measure the drive rotation speed. Could be the bearing is tired or stuck and it slows the drive down.
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Re: Floppy repair guides

Post by troed »

Kubik wrote:#2 - I'd try the diag cart, and measure the drive rotation speed. Could be the bearing is tired or stuck and it slows the drive down.
(Thanks, the fact that I have a diag cart just completely slipped my mind there)

1) Quicktest
"Disk A: SS Fail. Cannot write drive A: Fail at cycle:000001"

2) Read Alignment Disk
Reading track 40 just hangs - had to reset out
edit: The flappy disk (see below) makes one seek, then hangs. The other disks continuously seek over and over.

3) N/A

4) Disk Exerciser
F5 Write Protected Disk A: Side 0 Track 00
.. and then the same up to track 04 where it stops.
(No, the disk isn't write protected)

5) Check copy protect tracks
F5 Write Protected Disk A: Side 0 Track 80
Fails
(No, the disk isn't write protected)

6) Test Speed
Steady at 200 rpm
- but, and this might be significant. Only one one disk (and it also gives off a "flappy" sound when spinning). The three other disks I just tested with gives "Timeout waiting for index" instead. It's the "flappy" one that I had in mind when I said the drive felt tired - but rpm is obviously fine.

/Troed
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Re: Floppy repair guides

Post by exxos »

All the belt driven drives I've had here have had to have new belts, then they work fine after.

I've have no end of trouble with epson 380 drives lately, possible some others. Never had any spinning up issues. Some drives only seem to work by pushing the head down slightly. I've tried changing caps and messing about with these drives and just end up giving up with them.

It probably would be useful to document the model numbers and the faults you find with them. Ones which mostly work tend to be fixable with adding more caps. I've been doing that on the drives I've sold over the past several months.
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Re: Floppy repair guides

Post by troed »

So I spent yesterday going through my drives ..

#2 above is an Epson 380.

I had another Epson 380 laying around, and it showed mostly the same symptoms except _one_ single boot where I could suddenly hear motor going on and then it passed. And then nothing again.

I also had an Epson 480 that I've previously noted wasn't working as it should - and it produces better results, but something's not right when it steps. And the diag cart also shows that in all tests it's the "F4 Seek error" that happens. So if the stepping was "fixed" that drive would probably work.

And then I have another Epson 480 which I took from a 1040STFM (breaking the guarantee seal, yesterday!) which works just fine. I've put that in the Mega STE and now it lives.

The drive in my regular work STE (#1 above) I didn't do anything with yet.
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Re: Floppy repair guides

Post by frost »

Hello Troed and all,

Did you manage to get your faulty drives working ?

I hope you won't mind if I hijack this topic as I see a strange behaviour with one floppy drive that came from a 520 STf. At first, when I first booted the computer without putting a floppy disk into the drive, I thought the drive was broken as the motor spinned but the ST booted right to the desktop without showing the floppy drives. Then I tried to put a floppy disk inside and to my surprise, the ST booted, showed the unit A: and B: on the desktop and was able to read files without any problems. Btw, I tested on 2 STs, same behaviour. And the 2 ST work flawlessly with another drive that I know to work.

Has anyone a clue of what goes wrong ?

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Thomas
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Re: Floppy repair guides

Post by czietz »

With no disk inserted, afaik TOS relies on the "track 0" status line to detect if a drive is there. I.e. it selects a drive, tells the FDC to seek that drive to track 0 and waits for the track 0 line to go low. Maybe your drive is misconfigured (or faulty) and does not provide a "track 0" indication when no disk is inserted?
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Re: Floppy repair guides

Post by frost »

I guess the drive is faulty, as it's a STf type drive, with the big eject button. I have to get some testing hardware to go further in this problem, but it's definitely very helpful.
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Re: Floppy repair guides

Post by troed »

Over at a retro Facebook group a faulty Sony MPF110-03 (from inside a 520) turned up today. The symptoms were that it couldn't read or format any disks, it just seemed to seek slightly when accessing known good disks.

It was fixed by replacing the two caps (4.7uf and 47uf).
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