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Re: [midatlanticretro] can a terminal damage a computer?

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  • Mr Ian Primus
    It s going to be really rare for a terminal to damage a computer... beyond possibly burning out the 1488/1489 chips if there is something horribly wrong with
    Message 1 of 22 , Apr 7, 2013
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      It's going to be really rare for a terminal to damage a computer... beyond possibly burning out the 1488/1489 chips if there is something horribly wrong with the terminal, wired wrong, etc. From what I've read, RS232 spec was designed so that any of the wires could be shorted to any of the others without damaging it. Not that it's foolproof, but...

      Now, there is an exception here if there is bad wiring in the building. If the computer and the terminal are on separate circuits, and one device isn't grounded, AND another fault occurs, then Bad Things can happen, because it's very possible to get a 120v differential between grounds. But, this will be a rather spectacular show of sparks and burning smells. Not a subtle device failure.

      I have many dozens of terminals, and I've never had one damage a computer.

      I had one weird occurrence several years ago while copying some files on an Apple IIe, however. I had the Apple II connected to the PC's RS232 port, and was using Kermit to transfer some stuff back and forth. And, this was one of those rare occasions when all of the covers were actually on everything. Cover on the PC, cover on the Apple II, monitor sitting on top. It was winter, so the air was dry, and in my computer room, I had one of those plastic chair mats, and a wheeled office chair with plastic wheels. This room is wired correctly, and properly grounded.

      I had been typing on the Apple II, moved a foot or two to do something else, went back, and habitually touched the metal bottom casing of the Apple to discharge any static. I get a respectable static zap from it, and then start typing. The serial line isn't responding. I spend a few minutes checking cables, and assume that I must have damaged the RS232 chips in the Apple with the static. Swap out the SSC in the Apple - nothing. Then I happen to try the other RS232 port on the computer - it works. So, I'd burned out the RS232 chip in the computer. The original SSC from the Apple was fine. The only damage was the PC.

      Later on, I happened to have the computer apart and there was a little crater in one of the RS232 line driver chips on the computer's motherboard. Interesting that I was able to blow out the chip like that, with static, on properly wired, correctly grounded machines.

      That has never happened since, and I can't explain it. You'd think the static would have damaged the Apple before the PC - and either way, the metal casing of the Apple is directly grounded. So is the casing of the PC.

      -Ian
    • Wesley Furr
      Perhaps the chip was marginal to begin with, thus a very small jolt was enough to cause it to fail? Seems odd it would generate in the Apple II (where you
      Message 2 of 22 , Apr 7, 2013
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        Perhaps the chip was marginal to begin with, thus a very small jolt was
        enough to cause it to fail? Seems odd it would generate in the Apple II
        (where you touched) and go across the serial line without damaging the II...

        Wesley


        -----Original Message-----

        Later on, I happened to have the computer apart and there was a little
        crater in one of the RS232 line driver chips on the computer's motherboard.
        Interesting that I was able to blow out the chip like that, with static, on
        properly wired, correctly grounded machines.

        That has never happened since, and I can't explain it. You'd think the
        static would have damaged the Apple before the PC - and either way, the
        metal casing of the Apple is directly grounded. So is the casing of the PC.

        -Ian
      • B Degnan
        ... Thanks everyone for your useful suggestions. I was burying the ground line in a coffee can full of dirt but I should be adding water occasionally to keep
        Message 3 of 22 , Apr 7, 2013
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          Evan Koblentz <evan@...> wrote:

          >>> Bill might just be forgetting to turn the computer on!?
          >
          >There is precedent .... the time he declared our PDP-11/20 power supply
          >
          >dead, until yours truly observed that * the computer wasn't turned on
          >*. :)
          >
          >
          >
          >------------------------------------
          >
          >Yahoo! Groups Links
          >
          >
          >
          Thanks everyone for your useful suggestions. I was burying the ground line in a coffee can full of dirt but I should be adding water occasionally to keep it a little muddy. That keeps the electrons flowing better.
          --
          Sent from my PDP 8/e.
        • joshbensadon
          ... lol. On this note, I think the electric company may be giving us used electrons (and charging us for new ones). I have no way to verify this, does anyone
          Message 4 of 22 , Apr 7, 2013
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            --- In midatlanticretro@yahoogroups.com, B Degnan <billdeg@...> wrote:

            > >
            > Thanks everyone for your useful suggestions. I was burying the ground line in a coffee can full of dirt but I should be adding water occasionally to keep it a little muddy. That keeps the electrons flowing better.
            > --
            > Sent from my PDP 8/e.

            lol. On this note, I think the electric company may be giving us used electrons (and charging us for new ones). I have no way to verify this, does anyone here have an electron microscope?

            :)J
          • Jeff Jonas
            ... The Altair serial port blew one of those chips at the MARCH exhibit at the MAKER fair a few years ago. I m unsure if it was damaged there, or before. But
            Message 5 of 22 , Apr 7, 2013
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              I defer to Ian's experience:

              --- In midatlanticretro@yahoogroups.com, Mr Ian Primus <ian_primus@...> wrote:
              > It's going to be really rare for a terminal
              > to damage a computer... beyond possibly burning out the
              > 1488/1489 chips if there is something horribly wrong
              > with the terminal, wired wrong, etc.

              The Altair serial port blew one of those chips
              at the MARCH exhibit at the MAKER fair a few years ago.
              I'm unsure if it was damaged there, or before.
              But it sure ruined our day :-(

              > Now, there is an exception here
              > if there is bad wiring in the building.

              As you vividly demonstrated at VCF with your Prime :-/
              Perhaps I ought to demonstrate my
              fiber optic RS232 adapters.
              No metal between the systems,
              and it can reach over a km without repeaters!

              > I had one weird occurrence several years ago
              > while copying some files on an Apple IIe, however ...
              [static zap]
              > So, I'd burned out the RS232 chip in the [PC] computer.

              It's a crime not to socket those chips.

              <mild rant>
              The Univac is made up of hundreds, perhaps thousands of
              teeny PC boards because it required constant maintenance.
              Even televisions of the 70s were modular.
              But now everything's surface mount
              and so highly integrated into the motherboard
              that the mobo is considered a FRU (field replaceable unit).
              Happily, my car is not that way (yet!)

              <slightly off topic>
              Using a laptop/netbook/tablet (with software terminal emulation) with a USB to RS232 adapter sounds reasonably safe because the external adapter is the only thing at risk. Sadly, the Trenton Computer Fest's flea mkt is too small to offer them cheap as in years past :-(

              There are 2 chips inside those dongles
              - a FTDI FT232RL USB to serial adapter (or Prolific part)
              but that's 5V TTL serial
              (Adafruit's FTDI friend is just that chip
              http://www.adafruit.com/products/284 )
              - a Maxim MAX232 driver/buffer for TTL to RS232 levels
              with built in power supply so it's +5V only
              (also available as a teeny board:
              http://www.mikroe.com/add-on-boards/communication/max232/ )

              I just soldered up a RS232 to current loop adapter should MARCH need to interface to a current loop terminal.
              It's not opto-ioslated but it was good enough to be a kit!

              I'm unsure when or if I'll ever interface Bluetooth to that for wireless links to the vintage TTY.

              -- jeff jonas
            • B Degnan
              ... think. ... greatly useful was to put the devices on a ground fault interrupt outlet. If there is a ground problem then the GFI trips without destroying
              Message 6 of 22 , Apr 7, 2013
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                On 04/06/2013 04:37 PM, B. Degnan wrote:
                >> I have had a few computers fail while using my laptop as a terminal,
                >> recently. Is there something a rs232 port can do to a computer to
                >> cause it to fail, like the 1488/1489 drivers? Just seems odd. Corey
                >> was mentioning that he had problems with his laptop after upgrading OS
                >> drivers, but I have not done anything like that, I am using the same
                >> Win 2000 computer I have had for years. Thinking I am just being
                >> superstitious but thought I'd throw that one out there to see what others
                think.

                >As other have noted, could be grounding problems. One thing I've found
                greatly useful was to put the devices on a ground fault interrupt outlet. If
                there is >a ground problem then the GFI trips without destroying either the
                computer or the laptop. Also using a 1:1 transformer (Isolation
                >transformer) is probably not a bad idea.

                --------------------
                ------------
                ---

                But seriously, my problems are all independent of each other. I do
                everything through the grounded power supply of a battery backup with surge
                protector so I would think I would get bad news lights if there was a
                problem. I often solder at a different station than my laptop terminal.

                The 1488/1489's do die, and I have had to replace a few for sure. Better
                these than other parts.

                I have other devices that are quite stable with my laptop as the terminal.
                I think in my case it's just the computers/devices themselves, I try to not
                to short things but I am not the most dexterous.

                Bill
              • Dave McGuire
                ... [raises hand] I do. However, inspecting electrons with an electron microscope is tough, because you have to stain them for them to become visible. I once
                Message 7 of 22 , Apr 7, 2013
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                  On 04/07/2013 09:58 AM, joshbensadon wrote:
                  >> Thanks everyone for your useful suggestions. I was burying the ground
                  >> line in a coffee can full of dirt but I should be adding water
                  >> occasionally to keep it a little muddy. That keeps the electrons
                  >> flowing better.
                  >
                  > lol. On this note, I think the electric company may be giving us used
                  > electrons (and charging us for new ones). I have no way to verify this,
                  > does anyone here have an electron microscope?

                  [raises hand] I do.

                  However, inspecting electrons with an electron microscope is tough, because
                  you have to stain them for them to become visible. I once had a bottle of
                  stain that was made from quarks and muons, but the guy who sold it to me (who
                  had the oddest green scaly skin) isn't answering his phone anymore.

                  -Dave

                  --
                  Dave McGuire, AK4HZ
                  New Kensington, PA
                • joshbensadon
                  ... Perhaps the static only shorted one transistor, but if that transistor was the constant current source (now unlimited current source) for some other
                  Message 8 of 22 , Apr 7, 2013
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                    --- In midatlanticretro@yahoogroups.com, Mr Ian Primus <ian_primus@...> wrote:
                    > Later on, I happened to have the computer apart and there was a little crater in one of the RS232 line driver chips on the computer's motherboard. Interesting that I was able to blow out the chip like that, with static, on properly wired, correctly grounded machines.

                    Perhaps the static only shorted one transistor, but if that transistor was the constant current source (now unlimited current source) for some other transistors... then it's game on!

                    :)J
                  • joshbensadon
                    ... I think the best advice is to ground yourself more often. Like Ian said, he would touch metal before computer. I have personally seen in my professional
                    Message 9 of 22 , Apr 7, 2013
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                      --- In midatlanticretro@yahoogroups.com, "B Degnan" <billdeg@...> wrote:
                      >
                      > But seriously, my problems are all independent of each other. I do
                      > everything through the grounded power supply of a battery backup with surge
                      >
                      > The 1488/1489's do die, and I have had to replace a few for sure. Better
                      > these than other parts.
                      >
                      > I have other devices that are quite stable with my laptop as the terminal.
                      > I think in my case it's just the computers/devices themselves, I try to not
                      > to short things but I am not the most dexterous.
                      >
                      > Bill

                      I think the best advice is to ground yourself more often. Like Ian said, he would touch metal before computer.

                      I have personally seen in my professional work how some people are more likely to create a static charge. I don't know if it's clothes, physical chemistry or personality but there is a definite difference.

                      Before you work on that COSMAC Microkit, you better touch wood and metal!

                      :)J
                    • DuaneCraps
                      Josh, Unless you have a DC feed from the power co., you are not getting any new electrons , only the same ones jogged back and forth. You might, however, be
                      Message 10 of 22 , Apr 7, 2013
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                        Josh,
                         
                        Unless you have a DC feed from the power co., you are not getting any new electrons , only the same ones jogged back and forth. You might, however,  be sharing some with your neighbors who are on the same transformer. It might be worthwhile to invest in a whole house isolation transformer to assure that  you don’t get defective electrons from your neighbors. Can’t be too careful these days.
                         
                        Duane
                         
                        Sent: Sunday, April 07, 2013 9:58 AM
                        Subject: [midatlanticretro] Re: can a terminal damage a computer?
                         
                         

                        --- In mailto:midatlanticretro%40yahoogroups.com, B Degnan <billdeg@...> wrote:

                        > >
                        > Thanks everyone for
                        your useful suggestions. I was burying the ground line in a coffee can full of dirt but I should be adding water occasionally to keep it a little muddy. That keeps the electrons flowing better.
                        > --
                        > Sent from my PDP
                        8/e.

                        lol. On this note, I think the electric company may be giving us used electrons (and charging us for new ones). I have no way to verify this, does anyone here have an electron microscope?

                        :)J

                      • corey986
                        Yep I had a terminal Pop the serial driver chips, but the terminal was apparently hacked . When I found a switch inside that I flipped, it stopped killing
                        Message 11 of 22 , Apr 7, 2013
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                          Yep I had a terminal Pop the serial driver chips, but the terminal was apparently "hacked". When I found a "switch" inside that I flipped, it stopped killing drivers.

                          So in my case you could say the 1488/1489 drivers were not victims of normal circumstances, but of a short or mis-wiring.

                          In the end no biggie. I have a bunch of NOS drivers for my 3P+S, it's just my sio-A MITS serial card I'm won't risk on an unknown terminal.

                          Cheers,
                          Corey

                          --- In midatlanticretro@yahoogroups.com, "B. Degnan" <billdeg@...> wrote:
                          >
                          > I have had a few computers fail while using my laptop as a terminal,
                          > recently. Is there something a rs232 port can do to a computer to cause it
                          > to fail, like the 1488/1489 drivers? Just seems odd. Corey was mentioning
                          > that he had problems with his laptop after upgrading OS drivers, but I have
                          > not done anything like that, I am using the same Win 2000 computer I have
                          > had for years. Thinking I am just being superstitious but thought I'd
                          > throw that one out there to see what others think.
                          > b
                          >
                        • joshbensadon
                          The PC Museum here in Ontario has an IMSAI 8080 that I plan to get operational next weekend. It doesn t have the original 8080 board and without it the front
                          Message 12 of 22 , Apr 7, 2013
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                            The PC Museum here in Ontario has an IMSAI 8080 that I plan to get operational next weekend. It doesn't have the original 8080 board and without it the front panel can't work, so I've built a replacement 8080A cpu card and loaded it with RAM, I/O, and a Disk Emulator.

                            Does anyone have any CP/M software I can run on it for a decent demo? Wumpus perhaps?

                            Thanks,
                            Josh
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