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TRS 80 Model II Restoration Update

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  • B Degnan
    *TRS 80 Model II Restoration Update *After re-seating the chips and checking all of the connections, etc. I was able to get farther. Now the screen comes up,
    Message 1 of 4 , Oct 5, 2008
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      TRS 80 Model II Restoration Update

      After re-seating the chips and checking all of the connections, etc. I was able to get farther. Now the screen comes up, but I cannot boot any disks, even previously thought-to-be-working disks. Instead I get the following error:

      BOOT ERROR DC

      Here's what I found on this error:

      Floppy disk
      controller error.
      a. Defective a. Try a different
      diskette. diskette.
      b. Floppy disk b. Turn on the
      expansion unit. floppy disk
      not on. expansion unit.
      c. Defective FDC c. Contact RSSC.
      Chip or Drive.

      NEXT: Replace the disk drive with a replacement. Note - I am pretty sure I have at least one working disk, and I have tried booting with both a terminator in the expansion drive port AND also with a expansion drive attached to the port. I don't think that this is the problem.

      I have noticed that the system will notice if I put a disk in the wrong way, so I believe the controller is OK (or more likely to be). The drive belt spins the disk, but the drive motor does not move the head unless I extend it out manually. In this case it just returns it to track 0 and stops.  Maybe this is normal.  Maybe all my disks are simply bad.

      Anyone in the know here - If this happens to you, what turns out to be the common cause.  Am I correct to swap drives or do you think it's the controller?  I forget if there is a way to get into BASIC without a disk, and if so, I don't know if there are commands one can run to shake free a drive/test the stepper motor.

      Bill
    • Aaron Brockbank
      First off, hello to all MARCHians. Yes, I m from Australia, and have read this group for about a year. I m sorry if it s just for those on the other side of
      Message 2 of 4 , Oct 7, 2008
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        First off, hello to all MARCHians.

        Yes, I'm from Australia, and have read this group for about a year.
        I'm sorry if it's just for those on the other side of the pond, but
        when Bill needs help with his Model II, I felt that I should jump in
        now, and properly introduce myself in another message.

        Onto the post; B Degnan <billdeg@...> wrote:
        >
        > *TRS 80 Model II Restoration Update
        >
        > *After re-seating the chips and checking all of the connections,
        etc. I
        > was able to get farther. Now the screen comes up, but I cannot
        boot any
        > disks, even previously thought-to-be-working disks. Instead I get
        the
        > following error:
        > BOOT ERROR DC

        [snip]
        > NEXT: Replace the disk drive with a replacement. Note - I am
        pretty sure
        > I have at least one working disk, and I have tried booting with
        both a
        > terminator in the expansion drive port AND also with a expansion
        drive
        > attached to the port. I don't think that this is the problem.

        Which version of the FDC/PIO card do you have? One with two
        connectors (for internal and external drives) or one connector for
        both? Termination is generally only needed on the 'one for both'
        connection [the earlier of the two schemes].

        > I have noticed that the system will notice if I put a disk in the
        wrong
        > way, so I believe the controller is OK (or more likely to be). The
        drive
        > belt spins the disk, but the drive motor does not move the head
        unless I
        > extend it out manually. In this case it just returns it to track 0
        and
        > stops. Maybe this is normal. Maybe all my disks are simply bad.

        The normal boot action (after the "Insert Diskette" notice is
        cleared from the screen) is for the FDC to be sent a 'Force
        Interrupt' twice, then all drives are selected and stepped in
        (towards 76) by five tracks, and then drive 0 only is stepped back
        out to track 0. If drive 0 is not showing TRK0, the process is
        repeated twice more - if this fails then it displays ERROR DC.

        I'm assuming you have the later ROM that attempts to boot from any
        attached HD before Drive 0. I'm not sure about the earlier ROM, as I
        don't have a copy to disassemble and see.

        > Anyone in the know here - If this happens to you, what turns out
        to be
        > the common cause. Am I correct to swap drives or do you think
        it's the
        > controller? I forget if there is a way to get into BASIC without
        a
        > disk, and if so, I don't know if there are commands one can run to
        shake
        > free a drive/test the stepper motor.

        There is no BASIC in ROM on a Model II.

        If you swap drives, make sure that the last drive on any cable is
        terminated. What version of TRSDOS are you attempting to bring up:
        1.x or 2.0? Both can take some time to do their diagnostics before
        displaying anything.

        If I can help in any other way, please let me know.

        Kind regards
        Aaron (from Australia)
      • B Degnan
        ... Thanks Aaron. Our little group is becoming an international phenomenon! ... Two connectors. It does not hurt to use the terminator anyway, or just to
        Message 3 of 4 , Oct 7, 2008
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          Aaron Brockbank wrote:
          First off, hello to all MARCHians. 
          
          Yes, I'm from Australia, and have read this group for about a year. 
          I'm sorry if it's just for those on the other side of the pond, but 
          when Bill needs help with his Model II, I felt that I should jump in 
          now, and properly introduce myself in another message.
          
            
          Thanks Aaron.  Our little group is becoming an international  phenomenon!
          Which version of the FDC/PIO card do you have? One with two 
          connectors (for internal and external drives) or one connector for 
          both? Termination is generally only needed on the 'one for both' 
          connection [the earlier of the two schemes].
            
          Two connectors.  It does not hurt to use the terminator anyway, or just to see what happens.

          The normal boot action (after the "Insert Diskette" notice is 
          cleared from the screen) is for the FDC to be sent a 'Force 
          Interrupt' twice, then all drives are selected and stepped in 
          (towards 76) by five tracks, and then drive 0 only is stepped back 
          out to track 0. If drive 0 is not showing TRK0, the process is 
          repeated twice more - if this fails then it displays ERROR DC.
          
          I'm assuming you have the later ROM that attempts to boot from any 
          attached HD before Drive 0. I'm not sure about the earlier ROM, as I 
          don't have a copy to disassemble and see.
          
            
          I think I have a model from around 1980-81.
          There is no BASIC in ROM on a Model II.
          
            
          unfortunately!
          If you swap drives, make sure that the last drive on any cable is 
          terminated. What version of TRSDOS are you attempting to bring up: 
          1.x or 2.0? Both can take some time to do their diagnostics before 
          displaying anything.
            
          I have multiple disks of 1.x and 2.0.  What I plan to do next:

          1.   Test the disks on my known to work Model 12.  This way I can eliminate the variable "do these disks work?"

          2.   Test the expansion drive with the Model 12 (if possible).  This way I can eliminator the variable "does the expansion drive work?"

          3.  Swap out the drive 0 on the Model II, replace with a believed-to-be-new drive that I have had lying around for some time.

          4.  Test the working disks, and let you all know how it turns out.

          I may not get to this until the weekend, I have a packed schedule this week.

          Best

          Bill Degnan
          http://vintagecomputer.net - where I will also post pics and results.




        • Evan Koblentz
          ... read this group for about a year. Welcome! All are welcome. But I am curious how you found us!
          Message 4 of 4 , Oct 7, 2008
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            >>> First off, hello to all MARCHians. Yes, I'm from Australia, and have
            read this group for about a year.

            Welcome!

            All are welcome. But I am curious how you found us!
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