The Basic DISK II Pages
   Page No.:H084-2a
         the write protection and modifications of the write protection project  
The DISK][ Drive - a classic storage system

   Important Warning ! Never dismount or open drives unless they have been disconnected
   from the computer ( i.e. unplugging the drive from the diskcontroller ) and are without power !
   Disobeying may leed to a damaged computer or damaged drive !
Only in very few tasks power will be needed and
   this will be mentioned within the text at the correct place pointing to the needed precautions!
 page about write protection in the drive  back to previous page

 In former days using the old 5,25 " floppydisks and later the 3,25" disks the drives detected the write protection by the presence of a so called
 "Write protection notch".This notch was located at the right upper side oof the disk. Because in old days the floppydisks have been very expensive
 most users also used the revers backside of the disk to and in such a case they had to punch with a so called "disk-notcher" a second notch at the
 left upper side of the 5,25 floppydisk. In case that the notch was present ( or if the notchslider at the 3,25 disks where slided that way to open the
 diskwriteprotection notch the user could write data to the disk. If the notch was closed by a so called "writeprotection label" ( or at the 3,25 disks
 the slider was pushed towards closing the "writeprotection notch"  ) the disk was "write protected" and the drive refused writing data to the disk.

 To enable the writing again to the disk the user had to remove the disk "write protection label" or slide back the "write protect tab" to the position opening the
 notch again. In the early days the detection of the status of the write protection notch was performed with a microswitch and later that system was replaced
 with a light barrier system.


 In the classic DISK II drive of Apple the detection was performed by a microswitch that was located here:


 The pictures below show at left a closeup of the microswitch and the detection lever and at the right picture the opposite ( outside ) of the steelframe is displayed
 to show the adjustment-screw. In case of malfunction of the write protection often the lever is misaligned and by untightening the adjustmentscrew the switch
 with the lever can be adjusted again in a position where the switch surely indicates again the presence of a notch or itīs absence. Then the user can tighten
 again the adjustmentscrew in the re-adjusted position.


 At the drives of the Apple IIc the writeprotection is located here:


 In case of replacing the writeprotection at the AppleIIc drive with an alternating switch you can see how to perform that task in the pictures below:


You must pay attention at the pictures at the right side and the numbers marking the cable-block ! The picture shows the cable-block "twisted" around and viewing the reverse "backside"!

 At the DISK II the modification by adding an alternate write protection switch is shown in the next pictures first the "simple version":

 At the circuitplan and at Apple documentation this infoīs are relevant to the write protectionswitch ( the write protection line is colored ):
 the "luxury version" of the write protection modification is this way:


    download this page as PDF-file 

    turnback to previous page about DISK II ( speedadjustment)

    continue to the page about calibrating the track zero

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

    common mistakes at the Disk ][ drive and the controller

       making a homebrew replacement of the DuoDisk Cable
       due to european laws and german court decision:
 I hereby declare no responsibility to any "deep links" resulting from the links in this page. I have no influence to the pages linked hereby in this page and the
 contents in those pages. I therefor canīt take any kind of responsibility to contents in the pages, where these links direct the readers browser to nor to the
 contents resulting from following up links from those pages. The reference to contents by this links is dependent ro the status of the date when the links have
 been set ( April 2013 ) and it might occur that references and contents may change by the fact that domains may have been discontinued from their former owners.
 In such cases i canīt take any kind of responsibility to the changed contents. this is specialy valid to banners, advertisements or merchandising links in the targeted