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Re: [midatlanticretro] WTD: Morrow Wunderbuss Thinker Toys Motherboard Schematic/docs

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  • Dan
    I almost posted a lengthly explanation on the march group list before I noticed you posted the pic on cctech. The power supply in that circuit is a -12V not
    Message 1 of 12 , May 7, 2007
      I almost posted a lengthly explanation on the march group list before I
      noticed you posted the pic on cctech. The power supply in that circuit
      is a -12V not +12V. The voltage regulator part # on there is a 7912
      which outputs -12V. The part that is blown on there is an electrolytic
      cap, not a zener (note the + sign on each end of the cap). Both of those
      parts below the 7912 are the same type of part.

      Caps always dry up and blowout--they don't last forever. That's why it's
      good to have a Variac when powering equipment that hasn't been on for a
      long time--a homemade current limiter helps too if no variac is available.

      But I'm not sure of the value, it can't be very high in value, possibly
      only 3.3uf or 4.7uf considering the size, this isn't very critical , so
      long as you keep it in the ballpark. The caps for the 7805 regulator on
      there beside it are only 2.7uf. I would suggest changing both of them,
      for sanity's sake--they both might be damaged.

      The other important issue is to check the traces for damages when you
      remove the bad parts. They could have burned through creating an open
      circuit. So you'll have to splice the traces back together if this is
      the case. Some skinny telephone copper wire always does the trick. And
      last but not least, is the 7912 voltage regulator. You should check the
      -12V power before you plug in any cards.


      =Dan


      [ My Corner of Cyberspace http://ragooman.home.comcast.net/ ]



      B. Degnan wrote:
      >
      > Herb/Anyone else..
      >
      > I have a 1977 Morrow Wunderbuss "Thinker Toys" S-100 Motherboard with a
      > blown Zener diode near a 12+V position at the back of the board. Anyone
      > have a schematic? I checked Herb Johnson's site, there is nothing for
      > this
      > board listed. I would like to determine the exact type of diode so I can
      > replace it.
      >
      > What would cause a Zener diode to pop?
      >
      > Thanks.
      > Bill
      >
      > _
      >
    • B. Degnan
      Dan, As always, thank you for your help. Bill
      Message 2 of 12 , May 8, 2007
        Dan,
        As always, thank you for your help.
        Bill



        >The power supply in that circuit
        >is a -12V not +12V. The voltage regulator part # on there is a 7912
        >which outputs -12V. The part that is blown on there is an electrolytic
        >cap, not a zener (note the + sign on each end of the cap). Both of those
        >parts below the 7912 are the same type of part.
        ><snip>
        > The caps for the 7805 regulator on
        >there beside it are only 2.7uf. I would suggest changing both of them,
        >for sanity's sake--they both might be damaged.
        ><snip>
        >The other important issue is to check the traces for damages when you
        >remove the bad parts. They could have burned through creating an open
        >circuit. So you'll have to splice the traces back together if this is
        >the case. Some skinny telephone copper wire always does the trick. And
        >last but not least, is the 7912 voltage regulator. You should check the
        >-12V power before you plug in any cards.
      • Herb Johnson
        Bill Degan posted here a request for zener diode information for a Morrow Wunderbus card; he said I did not have that manual listed. Bill also sent me a
        Message 3 of 12 , May 8, 2007
          Bill Degan posted here a request for zener diode information for a
          Morrow Wunderbus card; he said I did not have that manual listed. Bill
          also sent me a request privately.

          In fact, I DO have that manual listed on my site, and I replied to
          Bill with some zener information. Meanwhile Dan replied here at MARCH:

          Dan <ragooman@...> wrote:
          >
          > I almost posted a lengthly explanation on the march group list before I
          > noticed you posted the pic on cctech. The power supply in that circuit
          > is a -12V not +12V. The voltage regulator part # on there is a 7912
          > which outputs -12V. The part that is blown on there is an electrolytic
          > cap, not a zener (note the + sign on each end of the cap). Both of
          those
          > parts below the 7912 are the same type of part.

          ..among other comments.

          This is why I don't do diagnosis of S-100 problems by email. There IS
          a zener diode on the Wunderbus, and I conveyed to Bill the information
          about it, and offered a manual to him. As for the picture, I've not
          seen it, so I have no idea what the actual problem is. I don't follow
          cctech simply because I can't keep up with traffic. I can't really
          keep up with it here "in" MARCH for that matter.

          For those who don't know: I have a very very large collection of S-100
          manuals, from which I offer good photocopies for a modest fee per
          page. Yes, there are free PDF's on the Web: my customers tell me that
          my copies are superior, and I have manuals not otherwise available.
          The fees I charge allow me to continue this service, year after year.

          http://www.retrotechnology.com/herbs_stuff/s100.html

          Oh, and the title at that home page advises "I let the MANUALS do the
          talking". Most S-100 manuals provide schematics, circuit and
          programming descriptions at length: some include source code listings.

          Herb Johnson

          Herbert R. Johnson, New Jersey USA
          <a href="http://www.retrotechnology.com/herbs_stuff/"> web site</a>
          <a href="http://www.retrotechnology.net/herbs_stuff/"> domain mirror</a>
          my email address: hjohnson AAT retrotechnology DOTT com
          if no reply, try in a few days: herbjohnson ATT comcast DOTT net
          "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
          S-100 IMSAI Altair computers, docs, by "Dr. S-100"
        • B Degnan
          Here is a pic of the effected area on the board: http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg Bill
          Message 4 of 12 , May 8, 2007
            Here is a pic of the effected area on the board:

            http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg

            Bill
          • Herb Johnson
            ... Shorted tantalum capacitors. They do that with age, short out and then try to conduct a few amps until they flame on. Literally. Schematic says....1 uFd
            Message 5 of 12 , May 8, 2007
              "B Degnan" <billdeg@...> wrote:
              >
              > Here is a pic of the effected area on the board:
              >
              > http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg
              >
              > Bill

              Shorted tantalum capacitors. They do that with age, short out and then
              try to conduct a few amps until they flame on. Literally.

              Schematic says....1 uFd (one microfarad). Probably should be 25 volts
              or higher. Mind the polarity when you install them! note the "+" markings.

              Herb
            • B Degnan
              Herb, Thanks. I am learning more every day, thanks to you and others who reply to my questions so kindly. Bill ... -END-
              Message 6 of 12 , May 8, 2007
                Herb,
                Thanks. I am learning more every day, thanks to you and others who reply
                to my questions so kindly.
                Bill

                > "B Degnan" <billdeg@...> wrote:
                >>
                >> Here is a pic of the effected area on the board:
                >>
                >> http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg
                >>
                >> Bill
                >
                > Shorted tantalum capacitors. They do that with age, short out and then
                > try to conduct a few amps until they flame on. Literally.
                >
                > Schematic says....1 uFd (one microfarad). Probably should be 25 volts
                > or higher. Mind the polarity when you install them! note the "+" markings.
                >
                > Herb
                >
                >
                >
                >
                > Yahoo! Groups Links
                >
                >
                >
                >


                -END-
              • Bob Grieb
                Nice photo. Made me want to get some marshmallows... Do you have fire insurance? ... __________________________________________________ Do You Yahoo!? Tired
                Message 7 of 12 , May 8, 2007
                  Nice photo. Made me want to get some marshmallows...
                  Do you have fire insurance?

                  --- B Degnan <billdeg@...> wrote:

                  > Here is a pic of the affected area on the board:
                  >
                  > http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg
                  >
                  > Bill
                  >
                  >


                  __________________________________________________
                  Do You Yahoo!?
                  Tired of spam? Yahoo! Mail has the best spam protection around
                  http://mail.yahoo.com
                • Dan
                  Herb, I like all of the back stories on your website regarding the history of designing all the vintage microcomputers. That s something I always like to
                  Message 8 of 12 , May 8, 2007
                    Herb,

                    I like all of the back stories on your website regarding the history of
                    designing all the vintage microcomputers. That's something I always like
                    to collect too, beginning with the minicomputer company where I used to
                    work, SEL. There's a good book, if you haven't seen it, it's called the
                    Engines of the Mind, where it has many of the back stories from the
                    early machines up to the microprocessors.

                    =Dan

                    [ My Corner of Cyberspace http://ragooman.home.comcast.net/ ]



                    Herb Johnson wrote:
                    >
                    >
                    >
                    > For those who don't know: I have a very very large collection of S-100
                    > manuals,
                    >
                    >
                  • Dan
                    At my old job(Lucent), I had to troubleshoot across the pond using a vnc server on a HP16500 analyzer (unix) and a Motorola processor emulator from Amsterdam
                    Message 9 of 12 , May 8, 2007
                      At my old job(Lucent), I had to troubleshoot across the 'pond' using a
                      vnc server on a HP16500 analyzer (unix) and a Motorola processor
                      emulator from Amsterdam to Chicago.
                      Always alot better than email but it helps with someone at the other end
                      to wakeup and turn on the equipment (the 6hr time zone didnt help
                      either--Shanghai was even worse).

                      =Dan

                      [ My Corner of Cyberspace http://ragooman.home.comcast.net/ ]



                      Herb Johnson wrote:
                      >
                      >
                      >
                      > This is why I don't do diagnosis of S-100 problems by email.
                      >
                      >
                    • B. Degnan
                      ... LOL
                      Message 10 of 12 , May 8, 2007
                        At 03:32 PM 5/8/2007 -0700, you wrote:
                        >Nice photo. Made me want to get some marshmallows...
                        >Do you have fire insurance?
                        >
                        >--- B Degnan <billdeg@...> wrote:
                        >
                        > > Here is a pic of the affected area on the board:
                        > >
                        > > http://www.vintagecomputer.net/Morrow/wuderbuss_mb_s-100.jpg
                        > >
                        > > Bill
                        > >


                        LOL
                      • jack99rubin
                        ... with a ... Anyone ... for this ... I can ... Being on the digest version of the list, I m a little slow to get messages and being disorganized enough that
                        Message 11 of 12 , May 9, 2007
                          :
                          >
                          > Herb/Anyone else..
                          >
                          > I have a 1977 Morrow Wunderbuss "Thinker Toys" S-100 Motherboard
                          with a
                          > blown Zener diode near a 12+V position at the back of the board.
                          Anyone
                          > have a schematic? I checked Herb Johnson's site, there is nothing
                          for this
                          > board listed. I would like to determine the exact type of diode so
                          I can
                          > replace it.
                          >
                          > What would cause a Zener diode to pop?
                          >
                          > Thanks.
                          > Bill
                          >

                          Being on the digest version of the list, I'm a little slow to get
                          messages and being disorganized enough that it took a couple of days
                          to find my Wunderbuss manual, I'm a bit slow to respond...I think
                          Herb pretty much covered all the relevant points.

                          All I can add at this point is that the tantalum caps associated with
                          the voltage regulators on this board are listed as 1 ufd on the
                          schematic and called out as 20v parts in the parts list.

                          Certainly no reason not to go with a higher voltage replacement -
                          these guys tend to provide a common source of entertainment on many
                          S100 systems and also frequently self-destruct on Heathkit H89
                          systems. Yet another good reason to avoid leaning over a vintage
                          system when you first power it up after a long rest.

                          Always glad to pay my respects to Chairman Morrow,
                          Jack
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