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Thread: Tektronix 4907 Floppy Drive

  1. #11


    One more 4907 update for today.

    It was pretty easy to convert one of the 4907's into a second drive enclosure.
    - change the drive select on the floppy in the 'slave' enclosure to DS1
    - remove the ribbon cable from the mainboard to the power supply board
    - use that ribbon cable to connect the two enclosures

    Everything works - UNIT 0 is in the master enclosure and UNIT 1 is in the slave enclosure. I did notice the UNIT Busy LED on the front panel is not working on the slave enclosure - signal could have been in the mainboard.

    Here is a photo of the stack of two 4907 next to my 4054A.
    There is also the 4050E01 ROM Expander and my small laptop on top of the 4054A.
    Below the 4054A is my Data I/O

  2. #12


    Good work getting the 4907 working and a really nice 4054!

    I would like to somehow emulate the 4907. Did you do any work on this or is it me remembering wrong? My GPIB project is still dormant.

  3. #13


    Quote Originally Posted by MattisLind View Post
    Good work getting the 4907 working and a really nice 4054!

    I would like to somehow emulate the 4907. Did you do any work on this or is it me remembering wrong? My GPIB project is still dormant.
    My GPIB project is still dormant too.

    But when I envisioned my project - I wanted to emulate the 4924 GPIB tape drive - but didn't have one.

    Now I have a 4924 tape drive - that I replaced the locked up capstan motor, and now use to rewind old tapes I have been replacing belts and recovering and posting the recovered files on my github site.

    I also now have a National Instruments GPIB to USB adapter that I have used with my HP 1630A logic analyzer to emulate an HP PCL printer and capture logic analyzer print output.

    Today, I expect to receive a Motorola 6800 CPU Preprocessor interface for the HP 1630A logic analyzer. I may be able to use it to debug the 6800 CPU in the 4924 tape drive issue with GPIB.

    If I get the 4924 working - I can dump 4050 to 4924 GPIB transactions - that I can use to emulate the embedded Tek BASIC interface to the 4924 that I want to emulate with Arduino code.

    I also have found in the 4907 Service Manual the 4907 test program written by Tektronix Support that shows RAW GPIB commands in the embedded BASIC ROM to the 4907. This may indicate a way to add "directory support" to the GPIB emulator - without needing the 4907 File Manager ROM cartridge.
    Last edited by nikola-wan; July 5th, 2019 at 03:36 AM.

  4. #14


    Here is a photo of loading the 4052/4054 Assembler program from the 4907 File Manager Unit 0 Floppy disk into 4054A memory, and then listing to the screen:

    First command at the top of the screen sets the 4907 clock date and time:

    CALL "SETTIM","08-JUL-19 20:01:00"

    That command only has to be done when the system is powered on. There is no battery backup, the clock is done in 6800 firmware based on a fixed interrupt period.

    Next, the command to mount one of the Unit drives, where A$ will receive the drive status.
    Unit 0 is the drive in the main File Manager system on top. Unit 1 is in the lower unit (ignore the 0 on that unit - I changed the drive address select to become the second drive).

    CALL "MOUNT",0,A$

    Next command lists all the files found on the floppy disk just mounted:


    The fourth file listed is "SCRATCHLIB/ASSEMBLER", where SCRATCHLIB is the default directory.
    So to load the ASSEMBLER program, you type:


    I then listed the program, which stops the listing when the screen is full until you press the PAGE key to clear the screen and the listing will continue.

  5. #15
    Join Date
    Mar 2006
    Salt Lake City, UT, USA


    Quote Originally Posted by nikola-wan View Post

    It sounds like you have a master unit - which only has a single drive and the dual floppy slave drive unit.

    You should only have to debug the single drive unit - if you have a working 4050 computer with the File Manager ROM Cartridge.
    They can also be used with some of the 411x terminals, IIRC. I'm not sure if any of my 411x terminals have the necessary I/O option in them for the external floppy drive. At least one of my terminals has the floppy drive integrated into the terminal housing and it's likely they used the same electronics and just placed it in the housing of the terminal instead of a separate enclosure.


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