MFM drives are really unreliable
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- เผยแพร่เมื่อ 28 ก.ย. 2024
- #retro #mfm #seagate
Last week, we took a look at five MFM hard drives and controllers used to hook them up to a computer. In this week's video, let's try to get those drives working.
Part 1: • Not forgotten: MFM har...
Part 2: This video
--- Info
Drives in this video:
Seagate ST-225
Micropolis 1325
Computer Memories Inc. CM 3426
PTI - Peripheral Technology Inc.
Seagate ST-4051
--- Video Links
Seagate ST-225 Service Manual:
www.minuszerod...
MFM hard drive emulator:
• This thing can backup ...
IBM PC AT 5170 Series (talking all about BIOS patching):
Part 1: • IBM PC/AT Model 5170: ...
Part 2: • IBM PC/AT Model 5170: ...
Part 3: • Fixing and improving t...
IBM PC AT 5170 Patched BIOS for faster hard drives:
archive.org/do...
SpeedStor:
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Spinrite II
winworldpc.com...
Mac 512k with a MFM drive inside:
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Thanks to the resourcefulness of my viewers, I've been pointed to the service manual for the ST-225! I love this community. www.minuszerodegrees.net/manuals/Seagate/Seagate%20ST225%20-%20OEM%20Manual%20-%20Oct85.pdf
Hey Adrian, thanks for the video; I was suspecting my hard drive to have scratches as well, so I followed your instruction to take the disks out in order to polish them - they do look fine now, after the polishing - but I forgot the right order to put them back in... does it even matter in which order I put them back in if I low format it?
...I'm obviously just kidding... 😂 great video mate! 😁👍
A lot of those drives even from that era may need to be actually 'PARKED' which could be a large cause of the not spinning up properly, or the heads not reading properly.
I have a few SCA SCSI drives and they make that sound quiet!
@@llwellyncuhfwarthen this also explains the high number of broken drives from the era... people turned off their computers without prior parking the drive properly.
Great content man, Thanks for the manual!
Many years ago I was given an ST225 with bad sectors in the boot tracks. With nothing to loose, I opened the drive and moved the track 0 sensor inwards a little bit. Closed the drive, formatted it OK and used it for years!
I had a 40 mb ide with a stuck stepper motor. I took the top off, gave the heads a nudge and put back together. Never had a problem after 😳.
My hvac class had a ps/2 that had bad sectors in the boot track as well. Just made a floppy boot disk, and all data and programs were accessible (including the games) 🤣
@@kd7cwg OMG yes I also had an old Conner drive that was pretty big for its time that I got at a computer market / hall with a bad sector 0. Booting from floppy then accessing it worked fine indeed! Man thinking about this I had so much old broken stuff I just bought from computer market junk piles for next to nothing that I got working through creative means. None of which I'd really rely on very hard, but eh it was good enough for hobby stuff. Also getting super cheap old SGI workstation monitors with weird connectors like 13W3 and getting them to work in linux by manually crafting X modelines until it gave a stable picture..20" CRT's that would heat your house for the price of a beer or two lol.
ST-225s are immortal.
The main trick besides not breathing over or talking near the drive while the cover is off is to *always* put the cover on with the drive spinning.
@@kd7cwg The system disk of my first digital recording studio's Atari refused to start one day, so I opened it up, gave a little spin to the platters and it restarted like nothing had happened. For the following few years the morning routine was open the drive, turn everything on, help the drive spin, put the cover back and just pretend it was normal :D
Brings back memories of what a PIA setting up a hard drive could be!
Indeed, heads, cylinders and sectors was a PITA. Varied from BIOS to BIOS
ruined the data on 0 track on someone one time thinking the settings on the PC was wrong and wasn't utilizing the whole drive.
Turned out back then the CHS on the BIOS was skewed to what the HD/controller expected.
Believe it or not, I was able to recover almost all of what was on the drive.
How you ask?
Folders are actually files, almost all subfolders and files were in folder, and almost everything on the drive was one cluster or contiguous clusters.
Using tools that could read the drive raw, searched for sectors containing '.' and '..'. Those would be folder entries.
Get the size of the folder, calculate the # of clusters, and slowly made a map of what the cluster table/File Allocation Table (FAT) should be. Get the file entries in the folder entries and repeat.
I only had a handful of situations where if I assumed contiguous clusters, I ended up with file chains that would appear to have cluster collisions.
Analyzed the data in the sectors assumed to belong to the files, and I could figure out where the next cluster actually was an for which file.
But when you only have a few 10's of MB, you could do that. Forget trying that with GB or TB!
Something I always used to do when testing hard drives, is I would always write the date when I wrote notes on the drive. Makes it easier on you in the future! Let's not forget, when you open these babies up, be sure to grab the neodymiums... Free magnets are always great. Fun stuff...
those don't use voice coils, watch the previous video
It was nice to hear those old Seagate drive sounds again. Growing up, our computers were made almost entirely of broken parts. The only reason we had hard drives at all was because they had died for someone else (mostly at my dad's work). For the most part, the old Seagates could be brought back with a low level format. Stiction was a thing, and we got in the habit of rotating the entire PC case while flipping the switch. They would occasionally get flakey again, but we kept backups. Later, Spinrite became a thing and it brought back those drives in-place, data and all. That tool was a godsend. We also had a 600MB Micropolis SCSI drive at one point that took so long to spin up that the controller would timeout. It was very loud, but was very reliable. Ah memories...
Upvote for the spin rite reference. That was an awesome tool
i saved many 'dead' drives using spinrite. stiction was definitely a thing with seagate st-225's made during a 4-6 month period, i have 2 st-225's in my 10mhz xt clone. the boot drive always starts up, the second one always sticks if it sits for more than a week. i was told that the stiction problem was due to the heads being too-well lapped and smooth, which causes them to stick to the platters. if the drive doesn't stick, it's because the heads are rough. go figure...
You know it's gonna be good when Adrian has to drop regular noise warnings in!
Sad to see none of those drives worked. Was fun to see the insides of them though! I’ve actually had incredibly good luck with MFM drives, and most of them I’ve gotten have worked fine with little effort. I actually just tested all of my spares recently and they all still work fine. Some of them I’ve had for years too.
I will go to great lengths to repair them sometimes as well. For example, I did a spindle motor replacement on a Miniscribe recently, which was 100% successful!
Obviously, I’ve definitely gotten some bad ones over the years though, but I’d say probably 80 percent or more of them I’ve bought worked fine in the end!
Seagate and “most likely to work” two things I never thought I’d hear together.
Thanks for this video! I remember the sound of the old ST-225 and similar drives. The good old days! You put forth a great effort on these. Much appreciated.
This reminds me of the efforts we make to un-stick antique refrigerant compressors which have become stuck from dried up oil or other problems. The only difference is that we use 240 or even 480 volts of raw power to get them broken free. Thankfully, opening them up doesn't equal death with these devices!
Yes, unless you burn out the windings, an old compressor is probably a lot hardier than a delicate hard drive of this vintage
this certainly was a blast from the past. I recall servicing drives suffering from "sticktion" or however you'd spell it. we called it that as well and the root cause I was given was that the spindle lubricant would cool and harden beyond the initial torque point of the spindle motor. as crazy as it sounds, the fix that worked most consistently for us was to actually drop the drive flat onto a table from a few inches up. well within the engineering g-force tolerances but enough of a bump to knock the spindle loose and boot the system for imaging.
Enjoyed seeing inside the drive while it was spinning and moving the head. Fun stuff!
I really enjoyed hearing those spinup sounds. Very nostalgic.
I had a ST-225 WAY back in the day. I'll note that those often get SUPER hot, which is part of what causes "sticktion". Even the best of them got hot enough to effectively melt and then boil away any lubricant used. I had one that after running for a day or two solid got hot enough to literally to unsolder it's own components. Seagate's answer to this was to always mount it with the metal body pressed against the cage to act as a massive heatsink. Always good to see older technology of yester-year.
Also, most of the ST-225 were from the age where you could use MFM or RLL. Given then RLL would make the same drive about 38M (vs 23M), I'd bet the one you had was formatted as RLL.
Whether the hardware works or not it is never a failure when you learn something useful, I call this a success with a twist.
Stiction was also an issue in large CDC sealed drives. We discovered that if the heads didn't move, the Teflon surface of the platter would get hot and effectively become an adhesive so when the heads landed, it would effectively "glue" the heads to the disk surface. What we finally ended up doing was modify the HD driver to rapidly move the heads around any time we went some number of minutes (I forget the actual time) without being accessed. We would that move the heads to a random sector.
Those old drives that had voice coils for the head movement have excellent magnets. I've got a couple of voice coil magnets from an old Micropolis 9GB SCSI drive and those magnets are super strong.
I had a Micropolis 1.2 G on my Amiga back in the '90s. One day I came home from work and I could hear it squealing before I got to the front door. Fortunately I was able to get all the data off of it by wearing tight headphones.
Wait... if it was running before you got home, who was using it? And HOW???
I never turn off my computers.
Years ago, I had a maxtor IDE hard drive with bad bearings, and oh my god that thing was loud. I'd have it running in a machine in the basement, somehow it ran windows 98 ok, and you could hear it clear from upstairs with the basement door closed. I also have an ST-225 MFM hard drive I'm trying to get working again, didn't think to use speedstor until watching this video. As always, thanks for the quality content!
I worked as a technician in the late '80s through mid-90s and we called it stiction too. I would lift the anti-static strap underneath and twist the spindle with a pair of needle nose pliers to get it started and then immediately back up the drive.
I enjoyed your video up to the last minute. I remember other HDU technology, called RLL or Run Lenght Limited, even more unreliably than MFM. Great video.
While working up at Seagate on contract got the opportunity to see them spin testing a large glass platter. That thing went off like a bullet! Forget what RPM they got it up to.
The fastest 3 1/2" drives were 15krpm. I believe I read somewhere that every attempt to go beyond 18krpm on commercial scale failed spectacularly. Also happened withCD/DVD drives that were 52x. A tiny imperfection of the disc was all it would take to shatter,
I live in maryland and there was a rock station out of DC and up to maybe 10 years ago they had some old computer running in the studio using a Seagate st-225 maybe ... just funny driving to work and I could hear that drive running in 20teens
Thanks for the video!
I had a seagate 20MB HD, probably the 225, that stopped working. So went out and bought another one. I think I paid $400 in '86 or so.
I too had the idea to swap the boards on the HD. BOTH WORKED! So then I had 40MB of storage. Whoo Hooo!
Your video brings back memories of the good(???) old days building/fixing/optimizing PC’s. Have forgotten how much an issue those old MFM/RLL disk drives had, esp. when larger drives came out that were not directly supported by the BIOS. Good walk down memory lanes. Thanks
You forget how noisy those old drives were. Even your home computer sounded more like a data centre.
I remember all those drives. The st225's always had problems, but could always swap the boards to get working drives out of batches of drives I would pick up. Still remember the days of nothing but noisy drives. My ears are still bleeding to this day from using whatever came in the door to give more storage space. Gone are the noisy, but fun days.
I remember them not being very reliable back in the day. I got my first pc a clone 286 because the mfm hard drive died and it was thrown out. I also remember that even later with some 386 clones that used ide that the bios was limited to specific drive geometries i used to get these very cheaply without the hard drives (not sure if they had broken or the drives were removed for security) there was a work round on these which i think was some sort of drive geometry translation utility, but i cant remember how it worked or what it was.
The ST-225 schematic is in the back of the ST-225 oem manual. Every time I post a link on TH-cam, TH-cam deletes my comment, but "minus zero degrees" has it.
Take the platters, drill a small hole near the edge. Take one of them and drill evenly spaced holes around it's edge. Suspend the single hole platters from the multi-hole one with light fishing line. suspend the whole contraption by fishing line strands attached to the multi-hole disk, and tied together. This gives you a great sounding wind chime. You can even drop one through the center with some salvaged polyamid cable to catch the wind & act as a clapper.
I owned a stepper-band driven SCSI hard drive for my Amiga 500. Yes they WERE that loud. I could hear it 2 rooms away, both the roaring of the fan/spindle and the chittering like a typewriter of the heads over the platters. They were bloody LOUD, Adrian. 🤢
That Micropolis drive is specified for 33 256-byte sectors per track. On a PC, sectors are 512 bytes, so that's why the capacity didn't match.
I remember some Winchester drives in a PDP-11 that sounded like a lot of loose change in the dryer when they spun up, but they worked fine! Compared to voice coil drives they are pretty robust.
Those were 14" RL01/RL02 possibly? I know there were some with 5MB fixed disk and a 5MB removable disk pack. These things were *loud* ..
"what am I doing watching someone mic up old hard drives" continues to watch.
I have an old Televideo 286 machine that has an ST-225 installed in it currently. I've made several attempts in the past to get the drive working, so I'm hopeful that I can apply what I learned from this video and give it another shot.
What's unusual about this machine is the floppy and MFM controller cards are integrated into a single card that was designed in-house by Televideo. The floppy controller part of the card works just fine, but the MFM controller portion seems to be completely dead. Although the chipset appears to be a common WD Winchester controller, I could not get Speedstor to recognize the controller at all, no matter what machine I had the card installed into. Either the card is so unusual that it's not compatible with my 486/Pentium machines, or more likely there's a fault with the controller itself. Perhaps the drive itself is dead, but I'm not certain because I don't have another drive or controller handy to properly rule out what's causing the problem.
Before someone asks, yes I'm the OP from that Vogons thread about said Televideo 286 machine. I made quite the blunder and decided to split open the drive to inspect the platters. Let's just say the other members in that thread weren't too happy about that. In short, I've since been on my own trying to figure this out. >.>
The drive platters make a pretty decorative mobile, I have one hanging in my window with a sign that says "Got Tape?"
I'm surprised this isn't a "II" video, but I'M HERE FOR IT. This episode borders on ASMR. Perhaps clip some out for shorts! LOL @ the QC Pass sticker.
Hey Adrian, do you still have that top board of that ST-4051?
I have a ST-4038 (which is the same drive, just with one less platter) with a broken top board. Mechanically the drive is in perfect condition, but there are a couple of broken components on the top board due to rough shipping.
It would be great if I could try to get that drive to work again with a donor board!
When I learned how to use MFM disks, Spinrite was the tool that they always told us to use to determine the interleave.
Please dig into the big drive. It would be interesting to see what's up with the drive.
I hope you saved the earth magnets inside the drives you took apart. They make awesome clamps for holding things in the workshop. Please be careful though when handling the magnets because they can really pinch pretty bad.
The really noisy drive actually had ferrite and copper disc material gouged out of the platters as if they were put through an engraving machine. When you spun it up without the cover, it sounded like Boston's MBTA light rail (We call them trolleys) pulling into Park Street and Boyleston stations. Look that up for the comparison! ;-)
I've taken many drives apart myself and yes, the parts are really amazing. It still amazes me today how complex they are and how much smaller the components have gotten while the storage has gotten bigger.
I had two of the magnets pinch the underside of my wrist. It took some skin with it. 😬
@@kd7cwg Ouch! That must've hurt!
I got my finger caught between them and ended up with a blood blister.
@@kd7cwg Ouch! Neodymium magnets are force to be reckoned with :(
Also at roughly 17:00 .. I had a weird one where a miniscribe mfm I had did what you had there.. wasn't initing properly. I could see the stepper motor moving so I assumed drive electronics. Then I exercised the stepper and felt it was a bit stiff.. used your video on lubricating those as a guide.. voila.. it worked. It had enough function to move the stepper convincingly, but not enough to move it all the way to the extremes for initialization I guess.
@16:26 -- there's that song that's like, "I whip my hair back and forth" -- I feel like this needs to be a t-shirt, "I whip my heads back and forth" with an Anthropomorphized harddrive doing that. 😅
Tbh the best part was seeing you have fun taking those drives apart haha!
I have had a lot of those ST-225 and don't think I've ever seen one with the SEAGATE logo on the bezel! Neat.
As for the loud drives I've had luck just letting them spin for an hour to loosen up the old lubricants. Plus I just love listening to them 😄
I've heard of an old hard drive cramming the head through its side, so I would not count on the electronics not allowing to move the head too far. We had a Seagate ST-157A at home (3,5" IDE). Long story short, due to some percussive maintenance, it got a bit of the case shaved into chips due to the platters hitting it. My dad opened the drive case, blew the shavings off, closed the case and it still worked flawlessly, not a single bad sector. Those things were rock solid, too bad Seagate hasn't seen that kind of build quality in pretty much decades...
You need a burst writer: Kinda like a servo writer, but those just needed the burst to be written. After it starts the YOUR heads are reset to track zero and knock against the backstop or inner stop, the burst is meant to stop this. I can't remember the actual name of the device off hand, but the inner tracks are written with a servo burst, the problem with these drives is that the head park area is over the burst area and so you tend to get head slap which is transit or shock damage caused by the heads leaving a group of four indentations. Without the burst data the head location when reset may end up several tracks in and not over the the outer track zero, if that occurs the drive will refuse to format. You can maybe adjust the head end-to-end backstops but this means opening the drive and definitely means rewriting the burst.
Those disc plates from modern hdd's are quite useful as a mirror when you shawing head with straight razor.
MFM drives were always terrible, but cheap. Easily serviced too. Considering the tolerances were gigantic by today's standards. For mobile computing, we tied them to our bicycles and rode all over town. You could basically fill them with sand, throw them at the wall, and still get them to work again. It's nice to see all the old fixes again, and so many ideas we never thought of.
I know the Micropolis HDDs Xerox used in their 6085 Star Workstation, made nearly zero noise. You had to crawl down behind the case and listen closely for any activity. While reading they made a noise which sounded like a very quiet coffee percolator. ;)
I remember in the late 90s I got an old MFM similar to your type 2. It wouldn’t be detected and quit. I ended up opening it and using speaker coil wire to connect the head to the board: ie the flexible cable toward the head was broken. I closed it and it worked. Out of 20mb, I lost some 2mb.
The Seagate 40MB HDD's used in A600/1200 had the sticky head problem.
I sincerely thank you for not talking and letting us enjoy the rare motor sounds!
I seem to remember some drives had a small hold on the bottom side where you would nudge a flywheel. The fault was rare where you would need to use that, because it only happened when the drive spindle happened to come to a rest at a "dead spot" between the coils.
A few even had black and white lines for usage with a stroboscopic light for fine speed adjustment.
If I remember correctly for an MFM hard drive to work the drive has to be formated with the specific MFM controler card. I was building computers back in the days when MFM and RLL drives were in use but I only sold new IDE drives. I had to recover a lot of data off MFM drives. Most of these were 10 to 20Mb and it could take several hours to pull the data off a drive.
I completely forgot just how loud those things were
Now I'm thinking to hook up all my old drives and move the bad ones to the scrap pile.
Back in the 80's to 90's I frequented a local repair shop to buy parts...I bought a bushel basket of MFM drive pulls for 10 bucks. There were 10 or 12 CMI drives and 6 0r 7 Seagates in there. I found out later IBM had to recall all the AT computers with the CMI drives - I took the tops off and the rust was slung off the platters on the inside periphery of the case..but I got 5 of the Seagates working.
Great video! I got once a bunch of old drives and turned their plates into fancy coasters
12:20: This is the first time I've noticed that Adrian's Digital Basement Quality Control sticker (on the FDD), and I just wanted to point that out. :-)
Your reactions to the hard drive sounds were awesome. It looked like the old family dog had passed wind next to you and it had just reached your nose.
I like your entertaining comments about "unhappy harddrives" and " belly up" (I did not know this phrase yet) companies, it makes me grin 😄 The sound reminded me of my first 20MB Kalok harddrive.😂 I have found an interesting "manual", it is called "CSC Hard Drive Bible 7th Edition 1994".
32:50 Oh come on, it just needs a little love and some oil, do not kill it. 🤣
I am so happy that my MFM HDD is Working Well. My ST-225 Makes the Knocking noise just at the beginning, and then it runs well.
OMG, the sounds that first drive made. It was begging for you to make it stop!!!! Hehehe...
Sticktion happens when the vax on the disk used on certain disks to protect against disk head crashes, melted during warm periods and after the disk spun down, it froze, leaving the head stuck to the platter.
My first drive was a Rodime full-height 5 1/4" drive hooked up to a CP/M system. This gave a whopping 4MB capacity. It couldn't boot from the harddisk, it needed an 8" floppy to run from. The disk controller actually didn't know how to seek beyond track 255. I reverse engineered the CP/M BIOS and got it to double the number of tracks, so I could do 8MB on a later Vertex drive of some type.
Had plenty of fun with Micropolis stepper motors going bad, Maxtor XT2190 sticking etc.
I don't miss those old hard drives. I do enjoy disassembling them with a 12 gauge slug though.
Those old cast iron shell turn to dust by itself.
That first drive sounded like something out of a horror movie, which would be appropriate if it had important data and started failing.
I remember having to create partitions, then format, when we disposed of hard drives we had to use software to delete everything on the drive, then rebuild them.
This brings back bad memories. We have become so spoiled with modern hard drives, and now ssds.
The technology behind hard drives is amazing. The distance between the head and the platters is far less than the diameter of something like the covid-19 virus particle. That's insane!
Not sure if that was the case with those old drives too, though.
I've been told that HDDs are some of the most precise mechanical devices ever made.
36:16 - sounded like a bad violin :D
Spinrite is one of the best utilities I ever purchased, although when I tried to use version 6.0 recently on a modern 3TB SATA drive it didn’t want to cooperate.
Excellent video as usual Adrian!
My first hard drive was a full height 10meg IBM 3030 drive. It was SO much faster than booting from floppies.
Years ago, I come across about 20 AT and XT PC's and near all MFM's (SEGATE 225 and KALOK I do not remember the model )and FDD's worked ! BTW I didn't knew about glass disk platters in the modern HDD's :)
43:12 that Micropolis disk looks like the rings of Saturn. Pop a ping pong ball in the middle to make your own ringed planet. 🪐
Back in the day, we used to call them MiCRAPolis.
i love what you do. i had to subscribe
Very interesting video. I recently had a hdd go bad and I let my young son take it apart. He was fascinated by it. Things didn't go so smooth when I asked him to put it back together lol
This is great! Lubricating oil for HDDs has come a long way! A little drop of oil in the right place would probably fix a lot of them, at least for a while. Too bad it's nearly impossible to get to those places.
still worth lubricating the bearings and stepper motors whenever this sort of stuff comes in, even if it doesn't work, gives at least a little bit better of a possibility that it works.
As I mentioned on part one of the MFM Drive Saga, I had a Seagate IDE ST-57A (that also has a stepper motor still) that I could get to cold-boot if I literally preheated it. I wonder if that also was the same 'stickiness' problem. It did however work for years with this problem as it was in a home server that almost never spun down. But 10 minutes at an oven on 50 degrees Celcius made it spin right up.
Also had another Quantum IDE drive of about 80MB that was stuck that I got working by opening it up and manually turning the motor. I was very careful to keep it upside down while open to avoid getting any or much dust in it. That one had a regular voice coild though. It survived for years as well, with 32KB of bad sectors.
By the way, you said that video was a bust. On the contrary! I've found it very interesting and have opened my fair share of (modern) hard drives.
Really interesting.
Always clean contacts with white rubber (the one for erasing pencils)
I actually miss the old hum of older hard drives and the click of the heads accessing data.
If these drives are like the old Quantum drives, most of those had stuck spindles. dropping flat from about 1-2 inches would free the spindle motor stuck bearing.
Uh, that brings back painful memories. The frustration, incredulity, and sadness. As a poor student, affording a drive was bad enough, forget about backups. When these drives died, they did without warning, and just like here, with teaser sounds that makes you think they might be a little alive. I do not pine for those days, hardware is so much more reliable today and spinning rust so cheap can you can raid it and have backups.
I was opening up one older HDD just yesterday and somehow the algoritm showed me this ;-)
The drive had more corrosion on one platter then yours... but as far as I know never been thrown in water. Must have sucked up all moisture from around.
I thrown out most of my old drives out some time ago...
1st HDD: Watch out!! it's an alien invasion!!!
Wow, throughly enjoyable to (of course) hear the sounds of these drives trying to start (the subtle beeps) and the dissection 🤣
And yes, these are last ditch efforts to try to resuscitate these drives once they're on the brink of death - certainly nothing that should be expected to be reliable in the end..
I'm reminded of the old XTs that one of my schools used to have. Their HDDs made adorable beep-like noises when seeking.
Is there some archive of HDD sounds? It would be interested to detect or try to guess manufacturer/model based on its sound.
I used service manuals from the manufacturer in the ARMY. I have never seen one sense but I am sure there are some out there somewhere.
Another fun thing you can get from trash hard drives are magnets, REALLY strong magnets used to move the head stacks.
They weren't 'that' loud, but not far off!
Actually, only modern 2.5" drives are glass. I've opened many dead drives and all the 3.5" ones have had aluminum platters. Also, the magnets in HDDs are endlessly useful. I also got a 2.5" IDE drive to work by opening it up. The top cover was slightly bent which prevented the motor from spinning properly. It worked long enough for me to copy the data off it which is all I needed.
Adrian invents the first electronic lathe
Probably outlast a modern drive
Those drives sound scary dangerous.
You know how friction has a coefficient of static friction before the objects start moving relative each other, and a coefficient of dynamic friction, after they start moving? Stiction is the "STatic frICTION", or the frictional force that keeps two objects in contact from sliding apart.
My main issue with MFM drives is stiction . I have a pair of Seagate ST 124's that will only spin up again reliably once you park the heads. These do not have auto park. The bigger 40MB ST251's do.