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Post-Trenton @ museum

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  • Evan Koblentz
    A few of us, led by Degnan, are coming back to the museum after Trenton (this Saturday) to work on the exhibits, etc. Degnan: It s very important that I attend
    Message 1 of 7 , Mar 6, 2012
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      A few of us, led by Degnan, are coming back to the museum after Trenton (this Saturday) to work on the exhibits, etc.

      Degnan: It's very important that I attend the Trenton evening banquet, so I will give my museum keys to you with some instructions, and I'll arrive in Wall a couple of hours later.
    • B Degnan
      ... OK. Anyone who knows about the following types of repairs is welcome to join me CBM/PET (I will bring what power supplies I have, IIRC MARCH s PET has a
      Message 2 of 7 , Mar 6, 2012
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        At 12:17 PM 3/6/2012, you wrote:
        >A few of us, led by Degnan, are coming back to the museum after
        >Trenton (this Saturday) to work on the exhibits, etc.
        >
        >Degnan: It's very important that I attend the Trenton evening
        >banquet, so I will give my museum keys to you with some
        >instructions, and I'll arrive in Wall a couple of hours later.

        OK. Anyone who knows about the following types of repairs is welcome
        to join me

        CBM/PET (I will bring what power supplies I have, IIRC MARCH's PET
        has a bad supply. I will at least determine if the 8V, etc is
        working, maybe set up a temp supply for testing

        PDP 11/20 - power supply testing and checkout. I have been working
        on H742 power supply systems in prep for this, assuming the 11/20 is
        similar enough.

        There's a short in the SWTPc 6800, not sure if this is fixed.

        remind me of the priorities. I know we wanted to try to get a mini
        running, I know most about DEC stuff so I will start there.

        etc

        Bill
      • Evan Koblentz
        ... Micros: - PET 2001 - SWTPc (short in cassette interface, I think) - Xerox 820 / IBM 5100 -- both have memory trouble As for the minis: If the 11/20 can be
        Message 3 of 7 , Mar 6, 2012
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          >> A few of us, led by Degnan, are coming back to the museum after Trenton (this Saturday) to work on the exhibits, etc.
          >>
          >> Degnan: It's very important that I attend the Trenton evening banquet, so I will give my museum keys to you with some
          >> instructions, and I'll arrive in Wall a couple of hours later.
          > OK. Anyone who knows about the following types of repairs is welcome to join me
          >
          > CBM/PET (I will bring what power supplies I have, IIRC MARCH's PET has a bad supply. I will at least determine if the 8V, etc is working, maybe set up a temp supply for testing
          >
          > PDP 11/20 - power supply testing and checkout. I have been working on H742 power supply systems in prep for this, assuming the 11/20 is
          > similar enough.
          >
          > There's a short in the SWTPc 6800, not sure if this is fixed.
          >
          > remind me of the priorities. I know we wanted to try to get a mini running, I know most about DEC stuff so I will start there.

          Micros:
          - PET 2001
          - SWTPc (short in cassette interface, I think)
          - Xerox 820 / IBM 5100 -- both have memory trouble

          As for the minis: If the 11/20 can be disconnected from the rack's
          overall power supply and plugged into straightforward 110, then great.
          If not, then we'll reconsider what to do.

          But, on Herb's page (in the section titled, "How did MARCH acquire the
          PDP-11/20?," -- http://www.retrotechnology.com/pdp11/) he wrote:

          "Main chassis without power supply, in rack mounting .... Power supply
          for above, H720e .... The power supply (included) has been separated
          from the main chassis for convenience in handling."

          I'm not sure if he meant the HUGE power supply mounted to the bottom of
          the chassis, or a smaller, separate unit that we stored someplace else
          -- if he meant the latter, then the good news is we know which one it
          is, because Jeff J. and I just saw it last weekend.
        • B Degnan
          ... OK...I will bring stuff for that. The IBM 5100 will be fun. ... Understood. ... I spent about 5 hours on my pdp 11/40 power supply this weekend. (H742
          Message 4 of 7 , Mar 6, 2012
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            >
            > >
            > > remind me of the priorities. I know we wanted to try to get a
            > mini running, I know most about DEC stuff so I will start there.
            >
            >Micros:
            >- PET 2001
            >- SWTPc (short in cassette interface, I think)
            >- Xerox 820 / IBM 5100 -- both have memory trouble

            OK...I will bring stuff for that. The IBM 5100 will be fun.


            >As for the minis: If the 11/20 can be disconnected from the rack's
            >overall power supply and plugged into straightforward 110, then great.
            >If not, then we'll reconsider what to do.

            Understood.


            >But, on Herb's page (in the section titled, "How did MARCH acquire the
            >PDP-11/20?," -- http://www.retrotechnology.com/pdp11/) he wrote:
            >
            >"Main chassis without power supply, in rack mounting .... Power supply
            >for above, H720e .... The power supply (included) has been separated
            >from the main chassis for convenience in handling."
            >
            >I'm not sure if he meant the HUGE power supply mounted to the bottom of
            >the chassis, or a smaller, separate unit that we stored someplace else
            >-- if he meant the latter, then the good news is we know which one it
            >is, because Jeff J. and I just saw it last weekend.

            I spent about 5 hours on my pdp 11/40 power supply this
            weekend. (H742 with H745/H754/H744's) That at least gives me the
            background about how to map out what's supposed to be happening, even
            if I simply diagnose the problems. It would be great to get just the
            11/20 system to power up, but we'd want to do a lot osystem checkout
            first. There are other DEC systems on hand I can check more than
            just the 11/20 as a candidate for "chase the lights" stuff.
          • jack99rubin
            ... Bill, The power supply for the 11/20 is single multi-voltage unit, more like an 8/E than the later multi-supply 11 s. You ll find all the info you need on
            Message 5 of 7 , Mar 7, 2012
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              --- In midatlanticretro@yahoogroups.com, Evan Koblentz <evan@...> wrote:
              >
              >
              > >> A few of us, led by Degnan, are coming back to the museum after Trenton (this Saturday) to work on the exhibits, etc.
              > >>
              > >> Degnan: It's very important that I attend the Trenton evening banquet, so I will give my museum keys to you with some
              > >> instructions, and I'll arrive in Wall a couple of hours later.
              > > OK. Anyone who knows about the following types of repairs is welcome to join me
              > >
              > > CBM/PET (I will bring what power supplies I have, IIRC MARCH's PET has a bad supply. I will at least determine if the 8V, etc is working, maybe set up a temp supply for testing
              > >
              > > PDP 11/20 - power supply testing and checkout. I have been working on H742 power supply systems in prep for this, assuming the 11/20 is
              > > similar enough.
              > >
              > > There's a short in the SWTPc 6800, not sure if this is fixed.
              > >
              > > remind me of the priorities. I know we wanted to try to get a mini running, I know most about DEC stuff so I will start there.
              >
              > Micros:
              > - PET 2001
              > - SWTPc (short in cassette interface, I think)
              > - Xerox 820 / IBM 5100 -- both have memory trouble
              >
              > As for the minis: If the 11/20 can be disconnected from the rack's
              > overall power supply and plugged into straightforward 110, then great.
              > If not, then we'll reconsider what to do.
              >
              > But, on Herb's page (in the section titled, "How did MARCH acquire the
              > PDP-11/20?," -- http://www.retrotechnology.com/pdp11/) he wrote:
              >
              > "Main chassis without power supply, in rack mounting .... Power supply
              > for above, H720e .... The power supply (included) has been separated
              > from the main chassis for convenience in handling."
              >
              > I'm not sure if he meant the HUGE power supply mounted to the bottom of
              > the chassis, or a smaller, separate unit that we stored someplace else
              > -- if he meant the latter, then the good news is we know which one it
              > is, because Jeff J. and I just saw it last weekend.
              >

              Bill,

              The power supply for the 11/20 is single multi-voltage unit, more like an 8/E than the later multi-supply 11's. You'll find all the info you need on bitsavers. Power to the bus is supplied through multiple paddles that insert into the backplane "above" the unibus, so it's very easy to isolate the supply by removing the paddles. This will still leave the fans (AC feed) hooked up to the main switch so don't worry if the fans come up when you think the p/s is isolated. The supply drops out of the chassis with a few screws and is pretty heavy so it makes sense that it was removed for shipping. It is approximately (from memory) 6x8x24 and sits in the side of the chassis. It is _not_ separately mounted. Vince Slyngstad suggested a nice way to start reforming the caps - grab a handful of 9v transistor batteries and appropriate snap-on connectors and just set up a battery on each cap for a while (I let mine sit for a week). The good caps reform and charge right up; leaky ones drain the battery. No muss, no fuss. Be sure to check for ripple - one of my 8/I supplies that seemed to be "about" right (voltage sort of close, but varying up and down a few volts either side of nominal) turned out to be mostly 120 Hz AC through a shorted rectifier leg. There's a lot of 8/I - 8/e in the 11/20 - chassis and hardware are quite similar, switches are the same, even though a different color, etc.

              Have fun,
              Jack
            • Evan Koblentz
              ... Yeah, that s definitely the component we saw last weekend.
              Message 6 of 7 , Mar 7, 2012
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                >> It is approximately (from memory) 6x8x24

                Yeah, that's definitely the component we saw last weekend.
              • B Degnan
                Thanks Jack helpful info. Fortunately my 8e has never needed any power supply service, but I can compare and contrast them then. bd
                Message 7 of 7 , Mar 7, 2012
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                  Thanks Jack helpful info. Fortunately my 8e has never needed any
                  power supply service, but I can compare and contrast them then.
                  bd


                  At 11:22 AM 3/7/2012, you wrote:


                  >--- In midatlanticretro@yahoogroups.com, Evan Koblentz <evan@...> wrote:
                  > >
                  > >
                  > > >> A few of us, led by Degnan, are coming back to the museum
                  > after Trenton (this Saturday) to work on the exhibits, etc.
                  > > >>
                  > > >> Degnan: It's very important that I attend the Trenton evening
                  > banquet, so I will give my museum keys to you with some
                  > > >> instructions, and I'll arrive in Wall a couple of hours later.
                  > > > OK. Anyone who knows about the following types of repairs is
                  > welcome to join me
                  > > >
                  > > > CBM/PET (I will bring what power supplies I have, IIRC MARCH's
                  > PET has a bad supply. I will at least determine if the 8V, etc is
                  > working, maybe set up a temp supply for testing
                  > > >
                  > > > PDP 11/20 - power supply testing and checkout. I have been
                  > working on H742 power supply systems in prep for this, assuming the 11/20 is
                  > > > similar enough.
                  > > >
                  > > > There's a short in the SWTPc 6800, not sure if this is fixed.
                  > > >
                  > > > remind me of the priorities. I know we wanted to try to get a
                  > mini running, I know most about DEC stuff so I will start there.
                  > >
                  > > Micros:
                  > > - PET 2001
                  > > - SWTPc (short in cassette interface, I think)
                  > > - Xerox 820 / IBM 5100 -- both have memory trouble
                  > >
                  > > As for the minis: If the 11/20 can be disconnected from the rack's
                  > > overall power supply and plugged into straightforward 110, then great.
                  > > If not, then we'll reconsider what to do.
                  > >
                  > > But, on Herb's page (in the section titled, "How did MARCH acquire the
                  > > PDP-11/20?," -- http://www.retrotechnology.com/pdp11/) he wrote:
                  > >
                  > > "Main chassis without power supply, in rack mounting .... Power supply
                  > > for above, H720e .... The power supply (included) has been separated
                  > > from the main chassis for convenience in handling."
                  > >
                  > > I'm not sure if he meant the HUGE power supply mounted to the bottom of
                  > > the chassis, or a smaller, separate unit that we stored someplace else
                  > > -- if he meant the latter, then the good news is we know which one it
                  > > is, because Jeff J. and I just saw it last weekend.
                  > >
                  >
                  >Bill,
                  >
                  >The power supply for the 11/20 is single multi-voltage unit, more
                  >like an 8/E than the later multi-supply 11's. You'll find all the
                  >info you need on bitsavers. Power to the bus is supplied through
                  >multiple paddles that insert into the backplane "above" the unibus,
                  >so it's very easy to isolate the supply by removing the paddles.
                  >This will still leave the fans (AC feed) hooked up to the main
                  >switch so don't worry if the fans come up when you think the p/s is
                  >isolated. The supply drops out of the chassis with a few screws and
                  >is pretty heavy so it makes sense that it was removed for shipping.
                  >It is approximately (from memory) 6x8x24 and sits in the side of the
                  >chassis. It is _not_ separately mounted. Vince Slyngstad suggested a
                  >nice way to start reforming the caps - grab a handful of 9v
                  >transistor batteries and appropriate snap-on connectors and just set
                  >up a battery on each cap for a while (I let mine sit for a week).
                  >The good caps reform and charge right up; leaky ones drain the
                  >battery. No muss, no fuss. Be sure to check for ripple - one of my
                  >8/I supplies that seemed to be "about" right (voltage sort of close,
                  >but varying up and down a few volts either side of nominal) turned
                  >out to be mostly 120 Hz AC through a shorted rectifier leg. There's
                  >a lot of 8/I - 8/e in the 11/20 - chassis and hardware are quite
                  >similar, switches are the same, even though a different color, etc.
                  >
                  >Have fun,
                  >Jack
                  >
                  >
                  >
                  >
                  >------------------------------------
                  >
                  >Yahoo! Groups Links
                  >
                  >
                  >
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