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PC 5.25" floppy disk drive repair

H

Half-Saint

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Does anyone here have experience fixing floppy disk drives?

I have two 1.2MB 5.25" disk drives that are faulty. The Mitsumi's head moves back and forth during boot but the spindle motor doesn't spin. I can move it by hand no problem. The second drive is a Teac FD-55GFR and this one also performs the floppy seek upon boot, spindle motor spins but it refuses to read any disks.

Any ideas?
 
The Teac symptoms are what I would expect from dirty heads. Try a cleaning diskette if you have one. Opening the drive to make sure the read/write heads are still attached is a good idea if the cleaning doesn't work. It is possible to clean the drive heads without a cleaning diskette but that requires a lot of care to make sure the heads aren't bent in the process. Be very gentle. There are other things that could be checked and adjusted like alignment but the ones I think of can take a lot time with limited chances of success so try cleaning first.

Mitsumi: I haven't found a manual for it. Couple of likely possibilities would be that the power connector has fallen off the spindle motor, the spindle motor itself is burned out, or if the drive has a belt, the belt has failed. Note that without a manual, I have no way of knowing if the drive had a belt. It's just that overall, belt failures are a common cause of drive failures.

Double check the jumpers. I doubt that would cause the symptoms but it is something easy to verify. Maybe take a few pictures of the drives with the cover off. Maybe something visual will provide a better clue as to the cause.
 
That first drive that does not spin - are you absolutely sure you don't have a cabling problem? What you describe is common if a wrong or faulty cable is used. Check the connector on the drive for any damage. Also check any jumpers on the drive's logic board, sometimes they can control motor enable. Check that any plugs or connectors going from the logic board to the motor are connected properly. I'd try manually enabling the motor enable line and see what happens.

The second one that does not read - what happens if you try to format a disk with that drive? Ideally, trying to dump a disk with a device like a kryoflux might give some idea of what the drive thinks it is reading, even if it not something a FDC will recognize (for example, no data at all, all static, a garbled signal, signal on the second head only, wrong track under the head, wrong speed, and so on).
 
Thanks for the input, guys. I forgot to mention that I cleaned the heads with a q-tip and some alcohol. I've done this many times so not worried about damaging the heads.

SomeGuy said:
That first drive that does not spin - are you absolutely sure you don't have a cabling problem? What you describe is common if a wrong or faulty cable is used. Check the connector on the drive for any damage. Also check any jumpers on the drive's logic board, sometimes they can control motor enable. Check that any plugs or connectors going from the logic board to the motor are connected properly. I'd try manually enabling the motor enable line and see what happens.
Click to expand...

I'm not sure which cables you have in mind? I used the same FDD cable to test both drives as well as a known working one. The 5-wire flat cable that goes from the main PCB to the motor PCB is soldered on both ends. I tested the voltages on the main PCB and they're 5V and 12V respectively so at least I know that the Molex connector and the attached cable are okay. I did remove the motor cover and everything looks fine inside at first glance. How would I go about enabling the motor enable manually?

SomeGuy said:
The second one that does not read - what happens if you try to format a disk with that drive? Ideally, trying to dump a disk with a device like a kryoflux might give some idea of what the drive thinks it is reading, even if it not something a FDC will recognize (for example, no data at all, all static, a garbled signal, signal on the second head only, wrong track under the head, wrong speed, and so on).
Click to expand...

I don't know what happens, I only tried to boot DOS from it. I'll give it a try when I have some free time. Unfortunately I don't have kryoflux.
 
I'll add one tip: Before you suspect that the drive alignment is off (it rarely happens), inspect the track 0 sensor. Remember that it's the reference point for all positioning. Very often, dirt can get into the works and affect where the drive considers track 0 to be. With a contaminated sensor, adjusting the alignment can be frustrating at best.
 
In my experience, 90% of Mitsumi drive heads have open coils at this point. It's actually rare I find one that still works. I guess the wires inside them have corroded with age. Especially most of my Commodore 1541 drives with Mitsumi/Newtronics mechs had bad heads now.
 
rittwage said:
In my experience, 90% of Mitsumi drive heads have open coils at this point. It's actually rare I find one that still works. I guess the wires inside them have corroded with age. Especially most of my Commodore 1541 drives with Mitsumi/Newtronics mechs had bad heads now.
Click to expand...

Maybe but the problem is not in the heads, it's something to do with the spindle motor.
 
rittwage said:
In my experience, 90% of Mitsumi drive heads have open coils at this point. It's actually rare I find one that still works. I guess the wires inside them have corroded with age. Especially most of my Commodore 1541 drives with Mitsumi/Newtronics mechs had bad heads now.
Click to expand...
We are talking about a 1.2MB PC disk drive here. Yes, the ones used in the 1541 are mostly all dead by now, but these are completely different drives mechanisms.

A non-working spindle motor can have many causes. It could even be just a wrong jumper set on the drive, causing it not to react to MOTOR_ON correctly.
 
SImple test for motor functionality: Hook the drive up to a power supply and ground pin 16. If the spindle motor runs, your problem lies elsewhere.
 
rittwage said:
In my experience, 90% of Mitsumi drive heads have open coils at this point. It's actually rare I find one that still works. I guess the wires inside them have corroded with age. Especially most of my Commodore 1541 drives with Mitsumi/Newtronics mechs had bad heads now.
Click to expand...

Strange, but I'm stumbling upon alot of Mitsumi 5.25" drives and all of them work perfectly fine... Maybe 1 per 10 or so has problems. While in case of Teac 55-series drives it's fifty-fifty. And the symptoms are like the OP described - drives spins and seeks, but won't read. Cleaning doesn't help. Sometimes it's an issue with jumpers (ie. some jumper fell off), but usually it's not. I havn't found a solution to this problem yet.
 
There's cleaning and then there's cleaning where heads are concerned. If you used your drive to scrape off the oxide from a bunch of Wabash floppies, isopropanol isn't going to do the job. Freon TF might, but you can't get the stuff anymore.

I use heptane, which is fairly friendly to plastics and does a good job of cleaning. Perchloroethylene is also okay, but not plastic-friendly.

If you think that cleaning up after Wabash floppies is bad, try it with a reel of 1/2" Wabash tape (and that's after "baking").
 
Chuck(G) said:
I've used a lot of Teac FD55BRs and I don't recall a single one of them ever failing. Maybe I'm just lucky.
Click to expand...

I have a box of around 5-10 dead 55BRs and GFRs :(
But again, those were floppy drives which were stored for long periods of time in (likely) harsh environment (like a moist basement or shed outside) I guess that properly used and serviced Teac drives will long forever.
 
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