Hi all,
this week @GeoffB17 (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1489) sent me a floppy drive to fix, unfortunately the diagnosis wasn't good. The stepper motor (the one that moves the head back and forth) was making ugly noises and wasn't turning although it was getting the right signals. As I don't have a replacement motor (donations welcome), I decided to open it up and see what actually failed. Unfortunately I discovered that there is a rubber seal inside that has the same problem that we well know from floppy belts - Over time they turn to a gooey molten mess. I wasn't aware that there was rubber in the motor and unfortunately it might spell the end to many drives in the future :( Below you can see my hurried, badly drawn diagram of what's inside:
[attach=2]
The armature (the bit that rotates) has a stainless steel shaft with a nylon bushing around it, on top of this is a rubber seal that the permanent magnet is pushed onto. I assume the rubber is used to give some cushioning to the sudden jolts that the motor takes. Either way, the rubber is now in a semi-liquid state and the permanent magnet now has enough movement to touch the surface of the electromagnets on the stator. This obviously stops the motor from doing its job.
Due to the fact that I don't have a replacement and this motor is dead anyway, I've nothing to loose by trying to fix it. So I've started this thread to document my ham-fisted attempts at dismantling the motor, replacing the rubber with someting suitable and putting it all back together again. The chances of success are probably about 1%, but I thought I'd try it anyway.
I'll take some photos of the real motor later before I start ripping it to bits. Stay tuned....
Bryce.
Good luck, bryce, that is a really difficult fix. I guess that, at some point, we will have to start to assume that it is time to forget about the beloved 3" units... :(
I'm not sure all versions of drives used the same type of stepper, so maaaaaybe they won't all have this weakness?
Bryce.
Interesting find.
That also may explain why some drive lose they head alignment.
What is the drive reference ?
Quote from: ||C|-|E|| on 14:53, 05 October 15
Good luck, bryce, that is a really difficult fix. I guess that, at some point, we will have to start to assume that it is time to forget about the beloved 3" units... :(
Maybe the stepper motor can be bought somewhere, but it may be hard to find.
Quote from: gerald on 15:03, 05 October 15
Interesting find.
That also may explain why some drive lose they head alignment.
What is the drive reference ?
I'll check and add all the details when I post pictures.
@TFM (http://www.cpcwiki.eu/forum/index.php?action=profile;u=179): Highly unlikely, unless the exact same part was used on some popular 3.5in drive?
Bryce.
KecskeBak on Twitter just said to hang on to the drive even if you can't fix it now as he's seen people 3D printing rubber parts. Apparently a new technique but in a few years who knows?
Quote from: TFM on 15:05, 05 October 15
Maybe the stepper motor can be bought somewhere, but it may be hard to find.
Probably in the the same source where you buy the acid chip, because the parts appears in brokersites search in stock.
Oh man :o
Maybe you can find something compatible from rubber/teflon/silicon based ring.
So I've just taken it all apart and it seems that my diagram above isn't quite right. The rubber seal seems to have been just at the end of the nylon sleeve. I'm kind of confused now as to how it really should be. As you can see from pictures 2 and 3. The nylon sleeve (which has cracked and broken at some stage) was inside the magnet, but there's no obvious sign of how this was bonded to the steel shaft, but I assume it was. The rubber ring was only at the end of the nylon ring. This would stop it from sliding off the shaft, but would not ensure that the magnet would turn the shaft. My plan is to repair the nylon sleeve and then see if I can securely re-attach it to the shaft, which is how I think it originally was. Perhaps the sleeve was just tight enough to grip the shaft at some stage, but it definitely isn't now.
@Gerald: There isn't any reference number on the motor itself, the drive is an EME-156 from a very early PCW.
Enjoy the pics...
Bryce.
Outer case with Electro-magnets inside:
[attach=2]
Permanent magnet and nylon sleeve on shaft:
[attach=3]
Magnet and sleeve removed:
[attach=4]
Shaft without components:
[attach=5]
Quote from: dragon on 16:35, 05 October 15
Probably in the the same source where you buy the acid chip, because the parts appears in brokersites search in stock.
Sadly not, I got my ACID chips from a company only dealing with chips. But there could be other sources, which I don't know about.
ah, but ist a simply motor no?. I mean it no have inside a circuit as the other motor in the fdd. In this case maybe a modern mottor can sustitute it.
The motor that turns the disk is just a standard DC motor, the circuit inside just regulates the speed. The head motor is a stepper motor, ie: it doesn't just spin, it jumps a defined step each time it gets an alternating pulse. Finding an alternative would be rather difficult, because the amount of steps (step angle), case size and shaft would have to be identical for it to be useful.
Bryce.
So, is this definitive? Anyone else experienced something of the sort?
Sorry for posting that here, but imho it's related. I got 3.5' floppy drive where the head is exactly one track off. Instead of track 2 the head is located on track 1 for example. Can this be fixed?
Quote from: TFM on 21:57, 10 October 15
Sorry for posting that here, but imho it's related. I got 3.5' floppy drive where the head is exactly one track off. Instead of track 2 the head is located on track 1 for example. Can this be fixed?
Hardly worth it is it? 3.5 inch drives can be had for next to nothing and are common as anything.
Quote from: chinnyhill10 on 22:09, 10 October 15
Hardly worth it is it? 3.5 inch drives can be had for next to nothing and are common as anything.
Well not so easy to get one with a working Ready signal these days. But you are right. I'm just curious. :)
Quote from: TFM on 21:57, 10 October 15
Sorry for posting that here, but imho it's related. I got 3.5' floppy drive where the head is exactly one track off. Instead of track 2 the head is located on track 1 for example. Can this be fixed?
@ TFM
That was a form of protection used by some Larger Businesses to stop staff taking data home on a floppy .
Ray
Quote from: Gryzor on 17:16, 10 October 15
So, is this definitive? Anyone else experienced something of the sort?
As Gerald mentioned, you do get drives that won't stay calibrated. You calibrate them and after some usage they are off again. It's highly likely that they are suffering from a similar problem inside.
@TFM (http://www.cpcwiki.eu/forum/index.php?action=profile;u=179): It depends how the calibration is done on that particular drive, but it should be possible.
Bryce.
Holy crap, it actually worked! I glued the plastic back into the magnet, put it all back together and the head moves. A quick calibration and it's reading disks like it should! Serious result, I really wasn't expecting much success.
Bryce.
Oh! That simple then :D
So, @Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) performs more miracles!!
Wonders what a 'bit of glue' can achieve, although I'm certain a lot of the miracle is hidden behind the words 'put it all back together'!!!
I'll be able to check out all the bits I've still got hidden on some of the 3" disks I've got. I think that for long-term, I'll go back to the 5.25 A: and 3.5" B: that I've got now, as those disks seem far more robust.
Geoff
Quote from: GeoffB17 on 18:21, 11 October 15
So, @Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) performs more miracles!!
He's like MacGyver or the A-Team :laugh:
Quote from: arnoldemu on 19:58, 11 October 15
He's like MacGyver or the A-Team :laugh:
So I only use a swiss army knife??? Or I shoot hundreds of bullets without ever hitting anyone? :D
Na, lots of tools, steady hand and lots of patience. That's all it takes. Really pleased with this one though. Another 3in failure that I now know is repairable.
Bryce.
LOL. You can fix anything! ;D
Quote from: arnoldemu on 20:03, 13 October 15
LOL. You can fix anything! ;D
Indeed he can if there was a 'retrofixer of the month' @Bryce would get my vote.
Quote from: CraigsBar on 20:30, 13 October 15
Indeed he can if there was a 'retrofixer of the month' @Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) would get my vote.
If we vote every month then his wall will be like this:
(http://vignette4.wikia.nocookie.net/spongebob/images/5/5b/Eotm.jpg/revision/latest?cb=20120927210402)
Garfield?
Spongebob of course, although I see myself more like Patrick :D
Thanks for all the positive words guys. Just happy that I can keep as much retro stuff alive a little bit longer.
@GeoffB17 (http://www.cpcwiki.eu/forum/index.php?action=profile;u=1489): Your drive was sent out Monday evening. Report back when you've given it a go. It would also be nice to know how long it actually continues working? I suspect it may work for many years yet.
Bryce.
It is great that you managed to fix it! :-* The same problem could happen to any of us and this would help a lot!
I considered doing a photo tutorial for the repair, but I decided it really isn't something that should be attempted without a lot of experience. There's just too many things that could go wrong and make the drive irrepairable.
Bryce.
However, if you have the pictures, this would make a good entry for the wiki :)
Mainly just the ones I've posted in this thread. For re-assembly, just look at the pictures in reverse order :D
Bryce.
Greetings all,
Just to confirm, I have just now received my drive back from 'The Magician'.
So far, it's working TOTALLY PERFECTLY - maybe even better that it ever was (certainly seems quieter than I remember). Really WONDERFUL!!
Million Thanks to @Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225).
Started checking through my pile of 3" disks, found a few things I'd 'lost'. Incl my 'tweaked' version of CP/M with an altered font (script). Also the bits from the disk that came with the DK sound module (not so much there, but one extra file that might contain something useful ??)
Geoff
And that's why I repair hardware. What a result. Really happy that I could help you get these treasures back. :)
Yes, every moving part is greased, so it's as quiet as it ever could be at the moment.
Bryce.
Ok, I guess I missed the point. What did you actually do? The plastic did melt and you replaced it by glue?
Sorry, I didn't get it. :-X
No. I glued the original plastic back in and remounted it without the seal ring. Then I recalibrated it and it worked and seems to be stable. No magic involved really. ::)
Bryce.
The problem is that, as Bryce said, the whole process is quite delicate and you need to have quite a lot of experience in order to make it work again :)
OK, it's only been a couple of days, but my floppy is still working.
Well, sometimes, I think it is - I have to strain my ancient ears to hear even a hint of any activity, but yes, the screen suggests that it IS doing something.
I was wondering about the perished rubber whatsit that caused the problem. Maybe it was a bad batch of rubber component, and other drives will not suffer the same problem. Maybe they did other batches a different way. I can well believe though that the idea of glueing would NOT have been practical for a production line, as I'd guess they would need to put the motor together and then test it, and it would not be a good idea to seal up until they glue had dried, and CERTAINLY not a good idea to test until glue had totally dried, so they would have had thousands sitting around waiting for glue to dry??
OK for @Bryce (http://www.cpcwiki.eu/forum/index.php?action=profile;u=225) to wait for ONE to dry, he could be doing something else.
As for whoever had the bright idea of using the rubber whatsit to speed up the assembly - I wonder if (s)he was expecting the drive to be still in use 30+ years later?? I'd guess not!!
Geoff
The bit I glued was the broken plastic, the glue doesn't replace the function of the rubber seal. I just ignored / left out the seal to see if it works without it, which evidently it does. The plastic/magnet isn't glued to the shaft, it is just re-mounted and held with pressure, which is how it originally was.
Good to hear it's still working though.
Bryce.
Excellent news that the repair is holding :D
And well done to Bryce for the repair work :D
Mark