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TRS-80 drive realignment experience

nice bit of work, tezza. i’m not familiar with Floppy Doctor—we used our own diags—but it seems to have worked well for you. good thinking on being a track off!

on those drives the head assembly is attached to the stepper with a metal band and screw. if that screw is loose, that could explain the noise and what caused your drive to fail. be worth checking if it fails again. not sure if it’s worth going back in to find out.
 
^^^^

I've had that set screw loosen in nearly all Texas Peripherals and Tandon drives that I own (some almost new). I think it takes one bad disk that causes the head to overstep its bounds (loud grinding) and alignment gets thrown off if that screw is the least bit loose. The first time it drove me crazy, align the drive perfectly and a day or two later it would be off again. Now it's the first thing I check. Never seemed to be an issue back in the day...never paid attention, but I wonder if they put a drop of loctite on those screws which didn't age well?
 
Problems which mysteriously appear and disappear always come back!

On the old C64 alps drives, there is a stepper motor pulley and shaft and eventually the head knocking will loosen them and it will spin in place. You can loc-tite it, or better yet, drill and pin it to fix it permanently.
 
tezza said:
I've written this drive alignment adventure up for those who might be interested.
https://www.classic-computers.org.nz/blog/2020-03-31-trs-80-model-4-drive-realignment.htm

Tez
Click to expand...

Thanks for the new article. I actually read your original article about the Philip Avery method to learn where things were and what to adjust. I went a little off book in that what i ended to doing was putting the floppy as drive zero, inserting a known good floppy in the drive, and i would adjust the screw a little and hit the reset button until it would boot properly. I tested and refined it afterwards with the floppy doctor disk . That seemed to get me there. I didn't have a scope at the time and meant to revisit later after i got one but it's been working fine so i haven't bothered.
 
Thanks for those comments guys. Yea, all the screws holding the stepper assembly did seem tight enough when I had to loosen them. That's not the say whatever they were screwed into did not go awry despite that. Anyway, yes, if it happened once and a reason was not discovered it might happen again. That's why I'll keep it as Drive 1 rather than Drive 0. With a FreHD to keep the Model 4 company, that's likely to be the least used drive in the whole system.

Tez
 
so, there are screws to align the stepper and there is a single screw that fixes the stepper band to the head. it’s the latter that we’re talking about.

C712BB79-D95A-4ACC-B03A-C6DC6C518190.jpeg

not my best artwork, but you get the idea. just want to make sure we’re taling about the same screw.
 
shank said:
so, there are screws to align the stepper and there is a single screw that fixes the stepper band to the head. it’s the latter that we’re talking about.

View attachment 60036

not my best artwork, but you get the idea. just want to make sure we’re taling about the same screw.
Click to expand...

Yea. Here's the Avery article (see link). The screws in Photos 1, 4 and 5 all seemed relatively tight when I came to loosen them prior to adjusting the cam screw.
https://www.classic-computers.org.nz/blog/2010-06-28-alignment-tandon-m100.htm

Tez
 
thank you for the articles, Yours and Avery's, since seemingly its impossible to find an alignment diskette now a days, I will work on the TP & Tandon 2a drives I have, to see if I can resurrect some "disk error" spewing ones.
I know a few other floppy drives are missing the (tm-100-a mind you) the soft counter pad to the head and I have yet found substitute to those but i guess that is another subject.
thank you again for the other ways to "align" a FDD.
 
on loctite... be sure to use the non-permanent kind.

substitute alignment disks could probably be made by writing a pattern on the “alignment” track and different patterns on adjacent ones. should see the difference with a scope easily. who has a drive in perfect alignment? :) that’s just head radial, there’s still track zero and index sector timing.

the head pad pressure “buttons” were a common replacement item. perhaps someone with 3d printer skills could help with replacements. i think a soft, durable fabric could work—maybe like corduroy, for the part that contacts the disk.
 
shank said:
the head pad pressure “buttons” were a common replacement item. perhaps someone with 3d printer skills could help with replacements. i think a soft, durable fabric could work—maybe like corduroy, for the part that contacts the disk.
Click to expand...

I do have a 3d printer but haven't had to repair these parts yet. I'll be honest though, I'll try to keep the drives working as long as I can, but I'm not going to put much effort into it. Unless someone does a kickstarter or something for new floppy disks (unlikely as the equipment and supplies to make them no longer exist), our efforts are much better spent in implementing non physical media solutions.
 
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