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Alignment problems

P

per

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Joined
Jan 21, 2008
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3,052
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Western Norway
I was normally using one of my XTs, and I did some general work writing to a disk in the B: drive. It all went fine, but after I replaced the disk with another; it stopped working. When I tried to read it, it just span and after a while it gave me an error.

I did some diagnostic testing, and it is not the stepper-motor this time (that was the cause with the A: drive). I also figured it was not the rotation speed, and most diagnostic tests didn't really show that anything was wrong. The only thing I was left with then was that it had problems locating sector 0.

Then I tried to format a disk in the drive. It all went fine, and the disk could be used, but only in the B: drive. The disk failed in the A: drive and any other drive I tried to use it in.

By this, I have concluded that at least one of the heads of the B: drive has come out of align. Then comes the problem. I have no idea how to ajust the aligment of those old FH tandon drives. I know there should be some screws somewhere, and that I need a specially formated disk with a matching program that generates some kind of sound when the heads are in align. However, I don't know where to find any of those.

I would be very glad if anybody could help me.
 
unfortunately, the drivers are easier to come by than the software these days i believe, i have a number of FH drives, 1 made BY ibm FOR ibm, 1 tandon and 2 cmi drives. Go CMI if you can find one, those far outlast their tandon brethren
 
k2x4b524[ said:
unfortunately, the drivers are easier to come by than the software these days i believe, i have a number of FH drives, 1 made BY ibm FOR ibm, 1 tandon and 2 cmi drives. Go CMI if you can find one, those far outlast their tandon brethren
Click to expand...

I did some more research and according to Tezza's website, the only thing you need is a good formated disk and an osclioscope. I got both, but not at the same place. I should also need the manual for the tandon TM100 drives.

This drive came original in this unit, and I don't really want to replace it. I'll try to do wathever I can to repair it.
 
per said:
I did some more research and according to Tezza's website, the only thing you need is a good formated disk and an osclioscope.
Click to expand...

Not quite. In the absence of an T-100 alignment disk, you also need software (or in our case another machine with software) which will allow you to position the drive head over a specified track. Philip Avery used a cunning workaround by hooking up the drive to his TRS-80 Model III and using diagnostic software available for that machine (Floppy Doctor) to hold the head over specified tracks.

per said:
I got both, but not at the same place. I should also need the manual for the tandon TM100 drives.
Click to expand...

Grab a copy of the SAMS guide at http://www.classic-computers.org.nz/temp/Tandon_TM100-2-sams.pdf . Let me know when you have it and I'll take it off the temporary site.

Good luck with the repair!

Tez
 
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tezza said:
Not quite. In the absence of an T-100 alignment disk, you also need software (or in our case another machine with software) which will allow you to position the drive head over a specified track. Philip Avery used a cunning workaround by hooking up the drive to his TRS-80 Model III and using diagnostic software available for that machine (Floppy Doctor) to hold the head over specified tracks.
Click to expand...
I'd problably have to make my own software for that. I should have enough knowledge to do it, although I haven't done any programming for the floppy drive before.

tezza said:
Grab a copy of the SAMS guide at http://www.classic-computers.org.nz/temp/Tandon_TM100-2-sams.pdf . Let me know when you have it and I'll take it off the temporary site.

Good luck with the repair!

Tez
Click to expand...

Thanks, but I already got it. BTW, the one I got has some extra pages and are at the size of 11.5MB.
 
per said:
I'd problably have to make my own software for that. I should have enough knowledge to do it, although I haven't done any programming for the floppy drive before.
Click to expand...

Sounds like a good project for those long winter nights. :)

per said:
Thanks, but I already got it. BTW, the one I got has some extra pages and are at the size of 11.5MB
Click to expand...

No worries. It's no surprise that there is more than one scanned copy sloshing around the Internet.

If you do manage to write a program that does this, it would be worth making it available to the Vintage computer community generally. Disk alignment issues are a common problem.

As Philip Avery had a solution to the issue with his Model III and Floppy Doctor software we didn't look for similar software for older PC-type machines. Maybe it aready exists out there somewhere?

Tez
 
Code to step to a particular track

Code to step to a particular track

tezza said:
Not quite. In the absence of an T-100 alignment disk, you also need software (or in our case another machine with software) which will allow you to position the drive head over a specified track. Philip Avery used a cunning workaround by hooking up the drive to his TRS-80 Model III and using diagnostic software available for that machine (Floppy Doctor) to hold the head over specified tracks.
Click to expand...
There is BASIC code for that purpose in the ComputerFacts for the Shugart SA-455. The ComputerFacts indicates that the code is for an "IBM PC or compatible".

The code in the ComputerFacts is in error: OUT 1009 should be OUT 1010. The code is listed below (with the error corrected)

Note that the code controls drive B: If you want control drive A: instead, change the three "OUT 1010,37" statements to "OUT 1010,20".


The following Basic program can be used to step the Disk Drive head to a specific track. The program is set up to operate Drive B. Press the CONTROL and BREAK keys at the same time to stop the program. NOTE: It is not necessary to insert a diskette into the Disk Drive before running this program.

10 CLS
20 OUT 1010,33: OUT 1010,37
30 S=INP(1012)
40 GOSUB 200
50 OUT 1013,7: S=INP(1012)
60 OUT 1013,2: S=INP(1012)
70 GOSUB 200
80 GOSUB 200
90 INPUT "ENTER TRACK NUMBER";TR
100 IF TR>40 THEN 90
110 OUT 1010,33: OUT 1010,37
120 S=INP(1012)
130 GOSUB 200
140 OUT 1013,15: S=INP(1012)
150 OUT 1013,2: S=INP(1012)
160 OUT 1013,TR: S=INP(1012)
170 FOR T = 1 TO 500: NEXT T
180 PRINT "PRESS ANY KEY TO STOP"
190 A$ = INKEY$: OUT 1010,37: IF A$="" THEN 190 ELSE 10
200 OUT 1013,8: S=INP(1012): S=INP(1013): S=INP(1012)
210 S=INP(1013): S=INP(1012): RETURN
 
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I think I got all I need now, except an analog alignment diskette. Well, I can allways use a normal working disk, but I don't really know how many voltage response I should expect when perfect aligment are reached.
 
per said:
I think I got all I need now, except an analog alignment diskette. Well, I can allways use a normal working disk, but I don't really know how many voltage response I should expect when perfect aligment are reached.
Click to expand...

In my Blog entry Philip Avery says "A good signal on my scope is about 0.3V peak to peak from TP1 or TP2 when reading over any given track.

Hope this helps

Tez
 
You know, it'd be a very simple task to create a digital alignment diskette. Simply either modify a hub cup or machine a new one to be offset (eccentric) by a fixed amount.

Format the disk up and write a simple program to read the IAMs (address marks) and display them. When you're at dead-center of the track, the IAMs at either extreme displacement from the center would not be readable.

Heck, make a nice well-calibrated rig to do this and sell alignment kits for $50 the each. Instant money machine.
 
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