---
title: "Resetting Track 0 and Other Tweaking"
type: "article"
slug: "resetting-track-0-and-other-tweaking"
url: "http://localhost/article/resetting-track-0-and-other-tweaking/"
markdown_url: "http://localhost/article/resetting-track-0-and-other-tweaking.md"
published_at: "2026-10-22T23:59:40+00:00"
modified_at: "2026-10-22T23:59:40+00:00"
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  url: "http://localhost/wp-content/uploads/2022/04/20230809-041332.jpg"
excerpt: "I wrote this originally a couple years ago and a recent conversation with Bob Swoger discussing resetting track 0 on a drive brought this to mind. While we both have successfully reset a Tandon TM 100-2A drive to track 0 again we both used different methods. While I haven't tried Bob's method I have heard/read…"
category:
  - name: "ZXir QLive Alive"
    slug: "zxir-qlive-alive"
    taxonomy: "category"
    url: "http://localhost/category/periodicals/zxir-qlive-alive/"
indiv:
  - name: "Bob Swoger (K9WVY)"
    slug: "bob-swoger"
    taxonomy: "indiv"
    url: "http://localhost/indiv/bob-swoger/"
  - name: "Donald Lambert"
    slug: "donald-lambert"
    taxonomy: "indiv"
    url: "http://localhost/indiv/donald-lambert/"
publication: "ZXir QLive Alive"
publication_r:
  id: 10286
  title: "ZXir QLive Alive!"
  type: "periodical"
  url: "http://localhost/periodical/zxir-qlive-alive/"
authors: "Donald Lambert; Bob Swoger"
volume: "2"
issue: "3"
issues_articles:
  - id: 26807
    title: "ZXir QLive Alive! v2 n3"
    type: "issue"
    url: "http://localhost/issue/zxir-qlive-alive-v2-n3/"
pages: "15-18"
pubdate: "Fall 1992"
archive_link: false
volumeissue: "v2n3"
---

# Resetting Track 0 and Other Tweaking

I wrote this originally a couple years ago and a recent conversation with Bob Swoger discussing resetting track 0 on a drive brought this to mind. While we both have successfully reset a Tandon TM 100-2A drive to track 0 again we both used different methods. While I haven’t tried Bob’s method I have heard/read of the set screw that locks the head assembly to the track stepping mechanism loosening which leads me to believe that his method might be best to use since you are moving the head back where it had been originally.

If a drive will FORMAT a disk and SAVE a file to it and can LOAD the files but no other drive will LOAD the files and this drive cannot load other drives’ files than either track 0 is off or else speed is off. (In early days of computing some computer manufacturers deliberately set either track 0 or speed off so that you had to use their repair services and had to buy disk drives from them.) All drive resetting methods require the disk drive power supply, a few tools and a working computer and disk drive interface.

### *** One word of CAUTION ***

IF THERE IS NO TERMINATOR RESISTOR IN THE SOCKET LOCATED BETWEEN THE TWO I.C.s IN LINE LEFT TO RIGHT WITH TP13 NOT ONLY WILL IT BE IMPOSSIBLE TO SET SPEED BUT ALSO IMPOSSIBLE TO SET THE TRACKING.

I had a drive that just seemed to want to vary the speed and also would not take a track adjustment until I realized that the resistor was missing.

### * Another word of CAUTION *

It might be safer to wrap masking tape on the screw driver shaft to insulate it. Also it is best to have a disk in the drive all the time that the spindle motor is running to put a load on it like when it is in use.

The first thing I did was check and reset the speed of the drive motor. For that you will need a fluorescent light and a small blade screwdriver to turn the adjustment screw in the potentiometer on the board on the end of the drive and you will need a jumper, a piece of insulated wire with a flea clip on each end to go between the square pins on the top board. With the disk drive on the table top side up and the drive door facing you, you will find a square pin located just to the right of the left hand board mounting screw by 5/16 of an inch and about a 1/16 of an inch closer to you than the screw and labeled TP10 (TP = test point) with the letters upside down. Fasten one end of the flea wire with the flea clip to the square pin. Up at the other end of the board is a row of connectors and the one labeled 11 will be directly in line with the square pin TP13 which is 5/8 inch this side of the connector. Fasten the other end of the wire using the flea clip to TP13 square pin. The purpose of the wire is to cause the disk drive motor to turn on when you turn on the power.

Speed is best set with a disk in the drive. I set the speed before I connected the interface cable to the drive. Now with the drive power cord plugged into the disk drive turn the disk drive on its side to expose the flywheel of the disk spindle with the paper and the bars printed on it exposed to the fluorescent light and watch the outer ring (60 cycle) and if the bars are seen to go either clockwise or counterclockwise then turn the screw in the end of the potentiometer on the back board (the motor drive board). The bars may waver but unless there is a definite movement in either direction the drive speed is correct, any movement should be seen in fifteen or twenty seconds. When the speed checks right remove the jumper between TP10 and TP13.

To reset the track stepping mechanism if the drive will not read track 0 (the directory of files) you will need a larger screw driver (insulate the shaft of the screw driver with tape) and an allen wrench size .109 or 7/64 of an inch. Turn the drive over and you will see down near the disk flywheel a pair of allen screws which are sealed on the side with green sealing material. Loosen the two screws and turn the drive back right side up and on the back of the drive above the disk motor board is a metal projection that has a slotted screw head in an oblong opening and with the drive door facing you the slotted screw will be on the right side of the metal projection. To the left and slightly towards you is another allen headed screw also with the green goop on the side of the head. You might make a mark on the plate next to the screw the location of the screwdriver slot for reference. Loosen that allen screw and test with the screw driver to see if the turning the screw moves the metal a trifle. The screw only has about a 180 degree adjustment (some drives will have 360 degree adjustment). I had the best luck adjusting by turning the screw to the most counterclockwise position.

The reason to insulate the screwdriver is to prevent touching the bare pins that stick out above the adjusting screw.

Now with the interface cable plugged in and the drive power supply plugged in select a disk SAVEd on a good drive (be sure to use a copy in case something happens to the disk) and first try to CAT the disk (I was using a TS2068 and a LarKen interface) when you get an error watch the metal slide and just turn the screw enough clockwise so that you see it barely more. Then once more re-try the CAT and repeat until suddenly the entire directory is listed as it should. I usually made one or two very slight more adjustments and then tried to LOAD a file on the first of the directory and then one on the last of the directory. If both had LOADed on a good drive and they LOAD on this one then power down and tighten the three allen screws and then re-try the CAT and the first program and the last program. If they LOAD you have it reset. With the LarKen and the TS2068 on failure to CAT you will get a CRC error and then garbage for the directory. Then as you get close to the track with the adjustments you might see one or two of the first files named then garbage, then suddenly all files appear. While the drives are rather mysterious (to me) in how they work it was rather more mechanical to make the adjustments. Of course other defects are handled differently.

I had one drive in which the track 0 switch was off. What it did was give a series of thunking sounds as it tried to read track 0. With the back of the drive facing you is the projection that holds the track 0 adjusting mechanism and to the right of that and slightly above it is a slotted screw with green goop on it. I adjusted that and the drive stopped clunking and loaded the directory. However, on another drive that did not help. I removed the spindle motor and then I could adjust the micro switch located where the track stepping mechanism could actuate it. Whether that adjustment was a fluke or not the drive could be reset on track 0 and it worked. While all the Tandon TM 100-2A drives look alike at a distance, close examination does reveal differences. I have one Tandon with a soldered in gang DIP switch in place of the DIP socket normally used for the jumpers for drive selection. Also, I have a drive labeled as a Texas Peripheral Co. but they used a Tandon frame including the TANDON name in the casting. But the other parts are not similar to the Tandon.

I now turn you over to Bob:

***

Don mentioned that I fixed a drive with the stepping motor set screw only but I wish to tell you that it took hours to accomplish. These drives probably fail in the first place because the screw that holds the stepping mechanism to the shaft of the stepping motor was too loose. It should be tightened first.

Don mentioned in his last paragraph that he heard the drive make a ‘series of thunking sounds’. This sound can be heard if the head tries to advance past track 83 or if it fails to activate the end of travel microswitch while seeking track 0. There are programs written with a bug that tries to send the heads to track 249. Since the drive can only travel to track 83, the head mechanism bangs until you turn off the system. If the head carriage, trying to travel past track 0, doesn’t activate the end of travel microswitch to let the system know that it has arrived, the head carriage will bang until you turn off the system. These two circumstances will cause the stepping motor shaft to slip inside the band spool if the set screw is the least bit loose.

The purpose of the screw Don mentions in his last paragraph is to push the head off the microswitch and back unto track 0. This screw is set to be just short of resting against the head carriage when it is over track 0.

Before loosening the three screws that hold the stepping mechanism in place, remove the top PC board and tighten the set screw on the stepping motor shaft. Then proceed as Don describes.

If you have a oscilloscope or capacitively coupled AC voltmeter handy, you may wish to make a final adjustment of the track setting screw in the following manner. Prepare a disk using George Chambers’ utilities that has been formatted and saved on a known good drive. Save a program on track 20 (middle track of a 40 track drive) that is about 5000 bytes long and LOADs itself continuously.

Place either a capacitively coupled AC voltmeter or oscilloscope between TP3 and ground. Load in the program and turn the track setting screw for maximum output on the AC voltmeter or both maximum amplitude and best symmetry on the oscilloscope. You will note that the signal level goes up and down, Use the lower level signal to set the screw for maximum as it is the signal from track 20. Tighten the three set screw down and check that the setting didn’t move.

If you do a VERIFY while watching the AC voltmeter or the oscilloscope you will notice that the output level goes down considerably as the heads travel to track 83, this is normal. It has to do with the fact that the data passing the head at track 83 is traveling so much slower than the data passing the head at track 0. An AGC circuit levels the output signal before it leaves the drive.

Thanks to Mark Farrell of the Glenside Color Computer Club of Illinois for the above education. –==Bob Swoger==–