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Tandon 5.25" FDD failure: Jammed stepper-motor

P

per

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Some time ago I posted about a problem with the FDD in my XT. It was concluded that the issue was caused by lack of lubricating, and it seemd lite it was fixed by applying something to lubricate the rails.

However, since then, the problem has reappeard several times (and quite often), so I think there must be something else wrong. Quite lately, it has gone really bad, and now the drive can't be used because it jams so often it's almost impossible to use it.

Some things I have observed are:
  • It seems like it only jams when the head assembly is returning to track 0.
  • After it jams, it will not move unless the computer is reset (then it tries to move it off the uppermost track durning initalazion, before it imediately jams again close to the uppermost track).
  • It seems to recover from a jam if the head is manually moved to track 0.

I think the stepper motor migth have some issues, or it may be the cirquits controlling the stepper motor. It may also be something wrong with the head assembly, but it's unlikely since it moves quite easily when the computer is off.

Any suggestions for fixes or similar experiences?
 
per said:
Some time ago I posted about a problem with the FDD in my XT. It was concluded that the issue was caused by lack of lubricating, and it seemd lite it was fixed by applying something to lubricate the rails.

However, since then, the problem has reappeard several times (and quite often), so I think there must be something else wrong. Quite lately, it has gone really bad, and now the drive can't be used because it jams so often it's almost impossible to use it.

Some things I have observed are:
  • It seems like it only jams when the head assembly is returning to track 0.
  • After it jams, it will not move unless the computer is reset (then it tries to move it off the uppermost track durning initalazion, before it imediately jams again close to the uppermost track).
  • It seems to recover from a jam if the head is manually moved to track 0.

I think the stepper motor migth have some issues, or it may be the cirquits controlling the stepper motor. It may also be something wrong with the head assembly, but it's unlikely since it moves quite easily when the computer is off.

Any suggestions for fixes or similar experiences?
Click to expand...
Sounds like you may have a problem with the track 0 sensor; can you step it manually back and forth by grounding the select line and pulsing the step line with the direction grounded or not grounded as necessary, and check the voltage on the track 0 pin?

http://www.interfacebus.com/PC_Floppy_Drive_PinOut.html

The signal lines are all open collector, so you don't have to worry about grounding them; a dual 5.25/3.5 cable is really convenient for this since you can use the 3.5 connector to insert jumpers.
 
Could be an open circuit winding (or duff contact or dry joint in drive circuit). Depending on how it's driven, a stepper motor will sometimes work for a seek or two provided it starts in the "right" position. Otherwise it just buzzes & fannies about aimlessly. it could be a shorted drive transistor, but that's unlikely as that tends to stop the motor moving altogether when on power.
 
On the TM-100-2 drives, the driver ICs for the positioner are particularly prone to failure. They're 2 8-pin DIPs near the rear of the PCB. I'd start there, as they're easy to replace.

Or just trash the damned piece of junk (is there any other 5.25" drive that has more problems than the TM-100?) and replace it with a Teac FD-55BR. :)
 
Chuck(G) said:
On the TM-100-2 drives, the driver ICs for the positioner are particularly prone to failure. They're 2 8-pin DIPs near the rear of the PCB. I'd start there, as they're easy to replace.

Or just trash the damned piece of junk (is there any other 5.25" drive that has more problems than the TM-100?) and replace it with a Teac FD-55BR. :)
Click to expand...

But the drive is original to that machine... I've been quite a perfectionist when it comes to exactly that system (only IBM cards, keep everything as original as possible).
 
I'm sure that others know, but without peeking at my O&A, I know that one of them was a CDC/MPI unit. Can't recall the other type off the top of my head...
 
Chuck(G) said:
I'm sure that others know, but without peeking at my O&A, I know that one of them was a CDC/MPI unit. Can't recall the other type off the top of my head...
Click to expand...
C'mon, Chuck, the Tandons weren't that bad...; FWIW, they used a lot of Qumes, but they might all have been half-height.
 
MikeS said:
C'mon, Chuck, the Tandons weren't that bad...; FWIW, they used a lot of Qumes, but they might all have been half-height.
Click to expand...

I went from Micropolis "built like a tank" drives to the Tandon TM-100. The difference in build quality was stunning. Some of the engineering was questionable.

When was the last time on this forum that floppy inquiries were dominated by "How do I repair my Teac FD55 drive?" questions?
 
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Chuck(G) said:
I went from Micropolis "built like a tank" drives to the Tandon TM-100. The difference in build quality was stunning. Some of the engineering was questionable.

When was the last time on this forum that floppy inquiries were dominated by "How do I repair my Teac FD55 drive?" questions?
Click to expand...
Wellll... I didn't say Tandons are great, just not quite that bad; you must be talking about different Micrapolis (oops, sorry, MicrOpolis) models, cuz I had trouble with every one of mine but out of more than a dozen TM-100-2s in pretty regular use only two or three had a problem in ~8 years or so.

No question that the Teacs (and other Japanese drives) were substantially better, but I think most of them are a little newer than the TM-100s, no?
 
What's a source for the analog alignment diskette, 224/2A, mentioned in the docs for these drives?
 
MikeS said:
No question that the Teacs (and other Japanese drives) were substantially better, but I think most of them are a little newer than the TM-100s, no?
Click to expand...

Not that much newer--and MPI/CDC and Shugart were exact contemporaries. Don't see many posts on those either.

Let's take some other products that Tandon was involved in. Kalok hard drives. JTS hard drives. Real quality stuff.
 
Chuck(G) said:
Not that much newer--and MPI/CDC and Shugart were exact contemporaries. Don't see many posts on those either.

Let's take some other products that Tandon was involved in. Kalok hard drives. JTS hard drives. Real quality stuff.
Click to expand...
Well, OK, no argument about Kalok and JTS, but at least in my experience the TM100-2s weren't that bad; considering how many more Tandons were in use (except for the old Perscis, Cromemco used Tandons exclusively, and every FH PC and XT drive I've seen has been a Tandon) it's not surprising that there are more posts about them than Shugarts (never seen a 5 1/4) or MPIs (have two, don't look any better than my TM100s). But like most of these differing opinions, it depends a lot on individual experience and judgement I suppose and you've no doubt seen many more drives than I have.
 
All I can say is that I really agree with Chuck !

Much past experience with Tandons - Teacs never had any issues.

Maybe there were some good Tandons and you got one - hearty congrats !

Check my past posts for more details.

The volume of Tandons for IBMs and Kaypros was astounding during that period - so expected "issues" and we got them.

But if you want to be a perfectionist, fine, but others want a working vintage computer to do things with and not be in the shop repairing it all the time.

Frank
 
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