APPLEBOX 
   
   

 
     The DISK][ Drive - a classic storage system
 

   

 
page about calibrating the track zero
 
 
  I really donīt want to disencourage anybody, but the task of recalibrating the track zero is really tricky, it requests some experience and its
  only possible to execute the task with special software and special disks - and its also strongly recommended that the user is able to handle
  ( with at least basic knowledge of ) and work with an osciloscope. there are different kinds of attempt to the task depending to the availiable
  items. If one of the listed items is missing it still might be possible to solve the task - but it becomes more complicated requests more time
  and more advanced experience to overcome such a handicap.

  I will explain the different possible tasks again in the order sorted by difficulty from simple to more difficult and finaly i will explain the
  "mission impossible" ( thats an attempt with missing tools and "try and error" method to get at least a drive able to read and write but
  but not with accurate calibration but rather more to say a "somehow acceptable result" ).
 
 
 
  First of all again weīll start with the basics - so lets examine how the Apple works normal, when it starts accessing a disk and what part 
  of the game the track zero plays in that game and what happens if the track zero is not recognized by the system.
 
  
Any kind of access to the disk performs the following steps:
1. recalibrate diskdrive ( thats the knocking noise when
    the read/write-head is pulled back to the outside of
    the disk and after the read/write-head sled hits with 
    the positioning-limiter some times the positioning
    stepper motor  and then moves the sled one step
    ahead towards the center and assumes this to be the
    track zero )
2. the controller tries to read this track and expects
    this track to contain the information determined to
    be at track zero ( this information track should
    contain the FAT and the information of the diskformat
    ( i.e. dependent to the operationsystem - how many
    tracks, the amount of sectors per track, the track
    where additional parts of the FAT is allocated and
    further information * )
    remark: FAT = File Allocation Table
                   * = further more detailed information at
                         the end of this page !
    The information in this track zero is normally written
    first time to the disk when disk becomes formatted or
    initialized by the INIT-command. Thereafter this track
    becomes updated, if the contents of the disk is
    modified (i.e.  update amount of free sectors ).
3. Then the read/write-head-sled is moved ahead
    towards the inner part of the disk to the desired
    track and sector to start reading or writing to the
    disk.
 
      4. In case of booting from disk its the same procedure and the steps from 1 to 3 are repeated step after step to get the data from the FAT,
          reading the sectors where DOS is stored sector by sector untill DOS is loaded completely to memory, then the computer performs the
          instructions of DOS itself - i.e. it looks for the program that was left as initial startup program in DOS - mostly common the "hello"
          program in DOS or the SYS-file in proDOS.

   *) this explenation is at the very end of the page !

     If one of the steps above fails the computer or DOS will display an errormessage ..... If the track zero isnīt found - the ROM F8 with the
     autostart routine will display the message "no System" or similar - if the mistake occurs later i.e. a part of DOS was not loaded the
     system will display a message like "read error" and if the mistake happens more later i.e. DOS loaded but "hello" not loaded due to
     malfunction the message will be something like "read error" or "missing file" or "file not found". In some occasions DOS simply crashes
     to the monitor-prompt.... this is for example a common kind of proDOS to crash.... with some experience and advanced knowledge you
     might be able to determine where the crash occured by the adress displayed at the monitor prompt..... - but thats another story....

    Before we start talking about the hardware here some things to remember / keep in mind:

    Of couse before taking next steps a cleaning and speedadjustment should be performed just to make sure that none of the other mistakes
    cause errors and making proof of the fact that the drive will be useable after readjustung the track zero...
( - at least, if you have another
    drive to boot from ).
    Allthough a drive might be misaligned - it still might be used.... the trouble is just that it canīt read disks from other systems and that disks
    written with this disk canīt be recognized or read by other drives
( so at least this should be detected before starting to attempt the
   hardware..... - if a second drive is availiable that is aligned proper you should set that drive to be first drive and move the misaligned drive to
   the second place to checkout some basic functions: does the drive pass the task of formatting  or INITīializing a disk and can the drive read
   back data that has been written to this disk by itself
( i.e. not from another drive written ) ? Does it pass for example a speedtest and certify
   correct speed ?
If it does and if the first drive can read write disks that can be exchanged with other drives because it is aligned correct, do
   you exchange disks containing data with other systems ? If not - you could for example dicide to use the other misaligned drive exclusive
   for own data and abuse that drive as a kind of encryptic security system, being sure nobody can access your private data .....
   Disks could be marked with special sign on label to indicate with which drive they may be used....
   Bear also in mind if you are using ADT this whole trouble might not bother you, if the disks you use are generated and used only by this
   drive...
  the trouble of misalignment only affects to you, when there is somehow a use with other drives too.....
   If you have judged this facts and dicide to proceed and go ahead to align the track zero, then go ahead with this page...
 
 
 So now after this basic explenation lets get to the hardwarepart with pictures and connect that with the explenation above......
 
First of all looking to the picture at the right side -
those parts that are not within the game of alignment have been cóvered with gray.


If you canīt read or remember the comment just switch back to the picture at page 1 to read within the large picture.

For this task only three groups become important:

       the fixed group of the 2 steelbars (1) and the
       topframe (2 ) that guide the sled.

       the sled itself (3 ), that carries the movable parts of
       the drive ( on top: diskcenteringwheel (4) , and the
       lever with the disk-pressdown-foam  (5) - on the
       bottom: the read/write-head (6) , the sledcarrier  (7)
       with the guidance notches (8) running along the
       steelbars (1), and
       very important: the steelspringplate
(9)  with the
       slideball (10), and the hardplastic positioningdisk
      
(11) with the guidingnotch for the slideball (12), and
       the slidinglimiter
(13) and
     
      at the bottomside the positioningsteppermotor (14)
      with its alignment screws
(15).

and now the pictures in detail with the mentioned parts (1) to (15):  
 
 
 Required Tools                                           

spacing template
Set with an .008 to .010 gage steel.
Apple says .010, but with .008 it will be rather better adjusted.

Such a tool isnīt too expensive and you can get it at ebay for about $5.
Of course better ones will amount up to $20 but probably you can lend it from somebody, who is familiar with repairing himself cars or motorsycles, because this tool is very common there - its needed to set adjustment at the mechanic of the ignition-breaker.

Other possibility of substitute will be a small drill that you know that it has the requested diameter.
   
 
 
   Parts to pay attention to    The numbers are corresponding to the numbers listed above !
 
 
 
   Dismounting the Drive

 
   
   Dismounting Analogboard

   The analogboard is rather simple to dismount: unplug at the front the cable to the
   read/writehead and pay attention not to issue any force to the thin cables themselve.
   The unplug the MotorPCB-cableplug in the center of the rear. Its a good idea to also
   unplug the cable to the controller.
   Then you might loosen the 2 screws at the front edges. The AnalogPCB then will
   slide forward toward the front out of the notches of the plastic Frame.
   Finally the drive then should look like this. Deposit the analogboard on a antistatic foam
   or in a antistaticsleeve!

   Next will be the dismounting of the topframe. Loosen the 2 screws at the rearside of the
   frame and the frame will slide with the frontdoor of the drive out of the notches of the
   frontpart of the drive. Be carefull at this step and donīt damage the lever of the toppart
   of the sled that carries the diskpushdownfoam.
   short remark besides: the diskpushdowmfoam can become a source of trouble when using both sides of
   a disk.... because if turning around the disk to write at the opposite side at the same time that material slides
   along the side that has been written..... if material became bad it can scratch the durface of the disk....
   so its very important that this material is soft and very clean ( without any kind of dirt ! ). So keep care of this !
 
   Dismounted Topframe



     The next step will be explained besides the next picture.

     First of all the cable to the Read/Write Head should be removed from the notches of the plasticframe
     very gently and carefully without damaging or tearing with force ! That cables are thin and very sensitive
     to force.

     Dismounting Steelbars

     In this step the steelbars will be dismounted. First the 2 screws at the rear of the drive shall
     be loosened and taken out. Then the centering screw with the centering blade at the front
     of the steelbars shall be released.

     Then the steelbars can be removed together with the read/write-head sled and the bars can
     be pulled out gently and carefully. Be sure to avoid any kind of force against the read/writehead
     itself and handle this sled with very much care ! Protect the read/write-head from dust or dirt and
     deposit it while  storage in a antistatic-bag !

      In this stage you will be able to see the entire positioningdisk - this one is still uncleaned and i want
      to guide your attention to the 4 small spotmarks drilled into the material. They mark 4 important points
      and are from the factory ..... they indicate the position where the steelball of the steelspringplate should
      be when the sled is positioned to "fixpoints" at :
      track 0
      track 20
      track 35
      track 40.
      This indicates that this positioningdisk was manufactured by a company, that also delivered this disk to
      thirdparty customers that made drives that also could handle 40 tracks ( as most of the drives could... ),
      the limitation to 35 tracks was also in those days rather unusual and it was related to the fact that Apple
      did not use specialized chips for diskhandling on their PCBs. So due to the use of standard chips the
      use of the "inner 5 tracks" ( with more compressed data and higher demands to the electronic read/write
      compensation were higher and Apple decided to stay away from this inner tracks and believed them to
      be not safe with the DISKII analogboard.
 
 
     Cleaning and lubbíng the positioningdisk

 
    

     In case of doubt please reread the explenations at page 1. Donīt use aggresive cleaning fluids !
     The positioning disk was cleaned with isopropanol-alcohol ( 70% ). Be sure to also clean every
     bit of dirt  out from the sliding-notch ! Then apply very few grease in the notch and wipe it all
     along the entire notch with a Q-Tip. Thereafter clean again the entire top of the disk with a soft
     tissue and just leave the grease within the glidingnotch. Then the disk should look like the one
     in the picture at the right side......
                and cleaning the Read/WriteHead

        Cleaning the read/write-head should be performed very careful.... avoid any kind of aggresive
        power..... donīt produce scratches and only use very clean isopropanolalcohol from a pharmacy
        with 70% to 95%.
Use a very soft tissue for cleaning and dry afterwards carefully and gently.

        Then you can start to remount the drive again. NEVER touch the screw that fixes the sliding-
        limiter ! It is upmost important to keep this part exactly in the position as it left the factory !

        The following pictures are just for information and display the parts in very detail to become
        familiar with the parts. Recognize the exact position and view of the steelspringplate !
        This is the very part that is responsible for the positioning of the sled and therefor extremly
        important later when calibrating the track 0 !
The steelball runs within the guidingnotch of the
        positioningdisk. It might turn out that the steelspringplate became weak throughout the years
        so its a good idea to bendup that plate a little ( not too much ! ) to make sure that later the
        steelspringplate will press down the steelball firmly in the guidingnotch - but not to firm !
        If the positioningdisk is turned the sled must slide gently and perfect forward and backward
        - but the steelslideball shall remain within the notch !
 
 
      The Read/Write-Headsled in detail

 
                                                                                                                
 
 
   Remounting the drive for alignment

 
      
      Put the steelbars again back in the correct position of the sled and apply
      a little grease to the steelbars and then just gently lay the steelbars in the
      position of the driveframe - at this moment the very position of the sled
      is not that important. Insert the screw and the alignmentplate at position 1
      and start gently to turn the screw till it gets grip in the frame..... then gently
      tighten the screw - but just that far that you still can adjust the position/length
      of the steelbars to make sure that they are plain with the backside of the frame
.
      Maké sure that there is space between the slidinglimiter and the axis of the
      positioningmotor. Now tighten the screw! Next you should insert the screw and
      the fixingplate at position no. 2....... and tighten that screw. up to this moment
      the position of the sled was not important due to the fact that the sled still is
      lifted up at the outer side a liittle bit. But now you should turn the positioning-
      disk till the steelslidingball slips into the guidingnotch and turning the disk
      moves the sled forward and backward. Move the sled somewhere to the middle
      range area and then fix the outer steelbar with the screw and fixingplate at
      position no. 3.
      Now turnback the disk clockwise till the sled is at the rearside and the slideball
      is just opposite to the drillmark that i explained few pictures above to indicate
      the position of track 0 like in the picture below at the right side.










     Text is continued in the next cell below.


   Now we will remount the topframe. Gently let the door slide into the notches (6) 
   of the frontpanel and make sure that the door is in horizontal position to make
   sure that the 2 metalclamps donīt block when slightly sliding in that door in
   position ... - then lift up the lever that carries the diskpushdownfoam so that the
   arm of the lever slips to the sliding area (5) of the topframe and then slide the  
   topframe gently to the position so that the hole of the rear steelblades are right
   on top above of the desired hole that are determined for the screws.

    Now tighten the screws 7 and 8 and donīt be irritated - when tightening that
    screws the topframe will lift upwards because this is the purpose of the
    steelplates at the end of the topframe. After the screws have been tightened
    you should add a little bit of grease in the notches at position 5 and 6 and
    shut and open the door to make sure that this does not cause noise and that
    the mechanic operates smooth and the door locks gently.
 
 
 
     Aligning the Track Zero

 
 
          A  - untighten the screws but leave them in the frame....
           they just shall be unfastened that far that the Steppermotor
           can be slided gently to both directions and thereby turns the
           positioningdisk at the other side smooth.....
           then follow the instructions below....
 
 
   Final remounting before testing with the software

 
    
      Remount the cable with the wires to the read/write-head very carefully the
      same way as displayed in the pictures at the right side and take care not to
      damage that thin and sensitive cables ! The black covers should be fixed in
      the notches and the cable should slide gently through that covers.... leave
      at the rearside enough cable that permits the sled to glide along the entire
      area without getting force applied to the cable.


     Take the analogboard and position it in the correct orientation and then
     let the board slide into the notches of the plasticframe at the positions
     G and then fix the screws at the positions H. Thereafter plug the read/write-
     head cable to the connector at position I and take care of the correct
     orientation indicated by the missing pol.  

     Then plugin the connector with the MotorPCB-cables at position J. Take
     care of the plastic lockers marked by the arrows ! Then plugin the
     flatribboncable at position K. Take care that the side of the cable indicated
     by a  colorside or with the brown or black  ribbonside is oriented towards the
     side indicated in the picture with pin 1.

     Remark: Its a common accident that the plug of the flatribboncable is pluged
     in the wrong way around at the controller and that kills chips in the electronics !
     So it is wise to also mark at this point the cable at the other side by a
     penmarker and mark the side where pin1 is at that plug at the controllerside
     too to avoid such an accident in the future !
 
 
    Now we are at the point that we can test the adjustment.
    If the drive passes the test itīs fine....
otherwise the entire procedures must be
    repeated with the alternating distanceblades.......

    Be aware that this test only works with the original disk and that copies of the
    disk or disks generated with ADT wonīt work ! In that case the only kind of
    verification will be, to boot from a disk written by a drive that is known to be
    aligned correct and then write a disk and try to read that disk completely in the
    recommended other drive known to be aligned correct !
 
 
 
 
   The only software that was released to the public, that offers a test of
   the track zero alignment is from Datalife the "
Datalife Disk Drive Analyzer" !
 
 
   
 
   
 
   
 
   
 
 
   If you went along the above displayed menus and options
   and recieved this display -  congratulations !
   Youīve solved the task successfully !
 
 
 
   This Part is related to the topic if you want to use the oscilloscope instead of the software

 

   If the Track is aligned correct the signal measured at Testpoint 2 ( in the circuitplan at the very right
   side ) in the picture of the analog board at the top left ( close to the read/write head connector )
   should look very similar to the picture of the right side.... - if the alignment is wrong the signal will
   have less amplitude and the signal will be "noisy" ( i.e. the signal wonīt be clear but rather more
   "disturbed by spikes" and "rounded edges" at the corners of the rising and falling edges. Also the
   amplutiudes if the single bits will be with "rising" or "falling" rooftops and the bottomline will be
   very "noisy" to because the read/write head will try reading beside the track....

   you might compare this to the driving with a car on the road..... if the car is on the road the noise-
   level will be low.... - but if you leave the road with 2 tires at one side "off from the road" those
   tires will be runnung very noisy in the dirt !
   
   
   
   
   
   






 

 
   *) Allthough the DOS ( Disk Operation System ) from Apple started with diskformat and a drive that only was able to handle 35 tracks - Steve
    Wozniak was aware of the fact, that within a short period of time drives could be availiable with more than 35 tracks and that the format of
     the disk might change (i.e. like the fact that first they started with 13 sectors and later changed to 16 sectors ) as it was also performed with
     the other larger computer of that days ( remember about the also common 8" diskdrives with more tracks and more sectors ).... not to forget
     that parts of the DOS-system from Apple were similar to other versions of DOS from those days ( it will go to far at this moment to tell stories
     about the influence of "big copycat Billy "the Kid" Gates" in the development of the DOS-version used by Apple  ..... thats a story for
     insiders...  )
     Besides the information of the format ao the disk the track 0 also contains the FAT or at least in one sector the information
     where the FAT is located on the disk ( tracknumber and sectornumber ... ) - this FAT ( File Allocation Table ) can be compared to the
     roadmap together with a adressbook - and it tells the computer which file is located in which track and which sectors and the amount of sectors
     used to store the file... if the FAT get larger the last sector of the track contains information in which track and sector the FAT is continued....
     ( this is for example valid for ProDos and there the track- and sectorinformation is converted to "blocknumbers" ) ... but in the days of DOS and
    CPM the space granted to the FAT was limited .... this was one of the reasons that at DOS the size if filenames was limited in length and the amount
    amount of files to be stored was limited to maximum of 96 files regardless if the disk was full or not.....

 
 
 
    download this page as PDF-file 

    turnback to page about speedadjustment of the drive

    turnback to page about basic mantainance of the DISK II

    continue to the page about advanced adjustment of the offset
    of the electronical Read/Write-Head compensation cycle