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Aligning Tandon TM100-2A - A whole track out!

mikeyp

mikeyp

Experienced Member
Joined
Apr 16, 2019
Messages
84
Location
Leicestershire, UK
I have picked up a cheap non-working Tandon TM100-2A. The drive is cleaned and lubricated but I can't get it to align. It's a whole track out! The cam only seems to want to adjust it within the bounds of the one track. I have it reading nicely, just to the wrong track. What do I adjust on this to make a more drastic adjustment and get it reading the correct track please? Track 0 does read correctly but from track 1 onwards it reads track ID-1 so 20 reads 19, 30 reads 29 etc.

A disk formatted in the drive itself seems to work ok though I suspect it would have issues since track 0 and 1 must overlap.

Testing for alignment is being done with a disk from the good drive. Testing from other known good drives can be done too if needed.

The image below shows my XT with some cards removed, good drive installed and new drive sitting atop the HDD.

By the way, replies to this will be quite delayed as getting this all out is a bit of a mission and can only be done when my wife isn't home...


image0.jpegimage1.jpeg
 
Image Disk aka IMD. See this page for info.

Seriously though, don't align drives if you believe them to be untouched. 99 times out of 100 they're just dirty. The heads just need a REALLY good clean with IPA and a cotton but and the rails cleaned and lubed. This one is WAY out and I have nothing to lose messing with it at this point.
 
Start with cleaning the Track 0 sensor. Dirt in that thing can really throw things off. I doubt that the radial alignment on a drive can vary the amount that you're claiming unless (a) someone has already tinkered with it; or (b) there's something seriously mechanically wrong with the drive.
 
Chuck(G) said:
Start with cleaning the Track 0 sensor. Dirt in that thing can really throw things off. I doubt that the radial alignment on a drive can vary the amount that you're claiming unless (a) someone has already tinkered with it; or (b) there's something seriously mechanically wrong with the drive.
Click to expand...
Good point I'll have a go at cleaning the sensor later. I suspect it has been tampered with. I have the other Tandon seen in the photo as well as several other drives which read the disks just fine. It doesn't appear to have anything significantly wrong with it other than having needed a really good clean and being WAY out of alignment. IMD at least identifies the track it's reading vs the track it thinks it's on which is why I provided the screen shot above where it's trying to read T11 but reading 10 instead.
 
The last Tandon drive that I worked on, the track zero adjustment had just completely come loose and I had to adjust it and lock it down again. That adjustment/lock screw is in the worst place ever. You have to remove the spindle motor to get to it.
 
Weird, I was just reading that Tezza link this morning while eating breakfast. BTW, my wife lets me take over the kitchen table with my projects when I don’t want to work in my basement workshop. ;)
 
I don't think it's the track 0 sensor, though it's related. The track 0 stop/adjustment must be correct as that's the only track that reads correctly. Various people have said both privately and in the thread modem7 linked to above that the carriage has slipped on the stepper spindle and I need to back it off a little on the spindle. Track 0 is determined by both the switch and one of the 4 positions/poles the stepper motor stops at. I'm not explaining it very well but I understand the logic. My plan is to adjust the cam adjustment screw to it's middle-most adjustment, head for track 16 where it will read track 15, loosen the screw on the stepper motor spindle, back off to track 15 without the carriage actually moving, tighten the screw, then hopefully adjust the cam until it picks up the track correctly.

It'll be a few days before I can try this so I'll report back when I do. If anyone has any further tips or advice on this, let me know. Thank you again.
 
Well, think about it--you have a stepper that's connected to a capstan wrapped with a taut band connected to the head carriage. The track 0 serves as only as a reference for the whole affair. When all's right with the mechanics, every track is a certain finite number of steps out from Track 0. If something is slipping or stuck, then you get problems.

Oh, BTW, did you check head azimuth? That can cause things to get progressively worse as you step in toward the spindle.
 
Don't know how to check the azimuth but I don't think that's out if what you say is true as it's consistent between tracks 1 and 39. I'm really hoping that is all that is wrong and nothing else will need adjusting.

I suspect the reason I'm getting track 0 correct is it's trying to move to -1 but is being stopped by the stop at the end. I'm going to leave that well alone. If I can adjust it back one track, it should start working.
 
In case anyone hasn't noticed over the years, I hate Tandon TM-100 floppy drives of any flavor. Back in the day, they were among the cheapest.
 
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