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Thread: Tektronix 4907 Floppy Drive

  1. #11

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    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

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    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

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    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

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    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:

    DIR2,"@"

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

    OLD "ASSEMBLER"

    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
    Location
    Salt Lake City, UT, USA
    Posts
    382

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    Quote Originally Posted by nikola-wan View Post
    legalize,

    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.

  6. #16

    Default EBAY 4907 and 4907 Option 30 two more 8 inch drives - both WORK!!

    Encourage by my success in getting two Tektronix 4907 drive systems working - I just received two more from EBAY, one more 4907 controller with one drive and one dual 8 inch floppy slave unit for the 4907 controller.

    Here is a photo of the dual drive slave unit - on top of my two 4907's:



    Before powering this unit on, I checked the following:

    • Rear Fuse - good
    • Power configuration - 120VAC good
    • Power supply board fuse - good
    • Unplugged all the cables to the two 8 inch drives to test the power supply board
    • Plugged in the power cord and turned on the switch
    • Rotron fan in the rear fails to rotate - checked the 120VAC to the fan - 120VAC is ok, fan has failed
    • Power supply +5V - good
    • Power supply +24V - not good


    Checked the service manual - you must add a jumper on the CONT pins if the Slave Drive unit is not connected to a 4907 controller.
    Plugged in the jumper - +24V good, removed the jumper.
    Turned off the power switch.

    I checked the stepper motor on both drives - one turned easily, one didn't turn.
    I put in an allen wrench into the setscrew on the stepper shaft and got it to start turning - I slowly moved the head back and forward and noticed the head seemed to catch at a couple of places.
    Both the Tektronix service manual and the Shugart 8 inch drive manual indicate - do not oil or grease the shaft.

    Plugged in the cables to the drives, connected the Option 30 two additional drives to my 4907.
    I left the cover off the two additional drives as in the photo above and pointed a desk fan at the drives for cooling.

    Both the left and right drives showed errors trying to read my formatted disks.
    I carefully cleaned the heads on both with isopropyl alcohol on a cotton swab.

    Now the left drive was able to read my formatted disks!

    The right drive gets an immediate error trying to read data on the first track - I'll work on this one later.

    Here is a screenshot of reading the disk directory on the left drive:



    Now it was time to test the 4907 that I purchased at the same time.

    I checked the rear fuse - the fuse ejector was broken, so I took a photo - it looked ok.

    I plugged in the power cord and the 4907 powered up and turned on the CLOCK LED, which I new meant the 6800 passed self test, memory test and was waiting for the clock time to be initialized.

    I connected this 4907 to my 4052, sent the CALL "SETTIM" command with the current date and time - and the CLOCK LED turned off - I think the 4907 is working.

    Now I inserted a formatted floppy, and CALL "MOUNT",0,A$ worked! I was able to load and run programs from that disk.

    Here is a photo of the EBAY 4907 - replacing the two drive Option 30 on top of my other two 4907's:



    And now for the finale - I inserted my new Adventure program disk and the game loaded and ran!



    The 4907 controller also had its fan fail - so I'll replace both of them.

    There were also a couple of cosmetic issues - the lens in the power switch on both units was missing, and the left drive write protect switch cover was broken off, and the switch was very hard to turn off. I can fix those too.

    All, in all - success in getting computer equipment dated 1979 working.

  7. #17
    Join Date
    Sep 2006
    Location
    Silicon Valley
    Posts
    2,242

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    Quote Originally Posted by nikola-wan View Post
    Encourage by my success in getting two Tektronix 4907 drive systems working - I just received two more from EBAY
    Nice to see you were able to save them.
    Did you get any of the tapes?

  8. #18

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    Quote Originally Posted by Al Kossow View Post
    Nice to see you were able to save them.
    Did you get any of the tapes?
    Al, yes I got eight tapes with them. I recovered all but the NAVY DEMO tape - which was on a Verbatim tape cartridge. I've had no luck recovering any Verbatim tapes - maybe they stretch?

    I'll be posting about the recovered files in my thread on 4050 programs.

    Monty

  9. #19
    Join Date
    Jul 2012
    Location
    Switzerland
    Posts
    115

    Default

    Quote Originally Posted by nikola-wan View Post
    Encourage by my success in getting two Tektronix 4907 drive systems working - I just received two more from EBAY, one more 4907 controller with one drive and one dual 8 inch floppy slave unit for the 4907 controller.
    So that┤s why I cannot find a 4907 : Monty is hoarding them all !

    Seriously, any chance of a 4907 firmware dump, if possible a straight dump of the 6800 ROM space ? ( i.e. with the patch rom details already included ? )

    Once you take modern RAMs and ROMs, leave out parity etc there is not al that much left of the 4907 hardware : a somewhat modernized copy of the hardware may be less work than re-
    inventing things from scratch... ( SD-cards etc etc )
    And the software would be identical.

    Jos

  10. #20

    Default

    [QUOTE=jdreesen;614275]So that┬┤s why I cannot find a 4907 : Monty is hoarding them all !

    Seriously, any chance of a 4907 firmware dump, if possible a straight dump of the 6800 ROM space ? ( i.e. with the patch rom details already included ? )

    Once you take modern RAMs and ROMs, leave out parity etc there is not al that much left of the 4907 hardware : a somewhat modernized copy of the hardware may be less work than re-
    inventing things from scratch... ( SD-cards etc etc )
    And the software would be identical.

    Jos[/QUOTE

    Jos,

    I consider it saving from the scrap pile ��

    I posted the auction on this forum and a Tek 4051 facebook group and after 2 weeks decided to buy them to get a real slave drive for me, and get more data points on the drive to drive incompatibility I’m seeing.

    I now have two drives that can reliably read each others data, one that reads mostly, one that begins to mount and then fails and one that immediately errors on mounting a good disk.

    I suspect drive alignment - but can┬’t find an 8┬” hard sector alignment disk.

    I believe the 4907 service manual quote - not to use a soft sector alignment disk as the drive wont be able to read disks from other drives.

    When this covid-19 pandemic is over, I plan to ask the Living Computer museum to loan me the two 8┬” floppies recorded by Tektronix to use to align all the drives.

    I have replaced the two bad Rotron fans with new Orion OA80AP-11-3TB fans and they work great and are quiet.

    I also found last night, the replacement C&K lever switch with LED to replace the broken front panel write protect switch and indicator: 7101J62CQE32 and ordered it.

    I will try to recover the ROM image as patched, but wouldn┬’t it be easier to capture the ROMs and Patch FPLA separately?

    I guess I could build a breadboard with address and data latches to capture the ROMs as patched?

    Jos, I would certainly like to send you a 4907 main unit - but shipping cost would likely be too high.
    Do you travel to the US?

    I think your idea of emulating the 4907 hardware instead of a tape drive has lots of advantages, although it would have to be combined with the 4907 file manager ROMs.

    I have found it very easy to mod 4050 tape programs for 4907 disk.

    Another advantage is the multiple directory support, which easily allows multiple tapes to be saved to one ┬‘disk┬’.

    Monty

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