Retrochallenge 2009
      Mark Wickens
      12-Jan-2009 20:01
                                       Hardware Issues

      So, I'm going to keep this entry short today, because I've probably been
      overdoing it a bit and my eyes are totally wonky. We had a risky deployment of
      code at work today - one that had been totally planned for, but an event that
      anyone in software knows attracts the gremlins - second only to demonstrations.
      As it happens, although there were a few issues and some initial excitement and
      investigation, the deployment went well and didn't have to be reverted.

      As if out of sympathy for the situation, however, the VAX 4000/90 started acting
      strange. Yesterday I had to reboot it because it had hung (or at least that is
      how it appeared) although in hindsight that may have been a similar symptom of
      the problem today. Yesterday a few computer-related items went a little bonkers,
      which means we might have had a power-spike or drop out. Anyway, today I noticed
      initially that the keyboard was only letting me type in UPPERCASE and I could
      not exit out of the ALLIN1 mail reader using the EXIT button. Then it got more
      serious - the HOLD, LOCK, COMPOSE and WAIT leds all lit up on the keyboard and
      it was game over.

      This particular LK201 had come in a shipment with a VT320 terminal from someone
      who had not been able to sell it on ebay, so I got the two for £5 plus £7
      shipping. They were both wrapped well but had clearly had a hard life, the
      keyboard being ingrained with a combination of dirt and sand - it looked like it
      had been stored in a garden shed for a few years.

      Most people who know me (and especially my wife!) know that I am partial to the
      odd keyboard of vintage era. I 'cut my teeth' on an 80's vintage IBM Model M[1]
      and have owned various other keyboards, including the Gateway 2000 programmable
      keyboard[2], the PFU Happy Hacking keyboard[3], Sun Type 5 keyboard. In terms of
      Digital keyboards, the VAX 4000/90 came with an English and German LK401 and
      then I have purchased a couple of LK201s[4] - my DEC 3000/600 came with the
      LK421[5].

      I generally strip down the keyboards and give them a good clean when I get them.
      I looked around for the best way of doing this (including using a dishwasher -
      don't leave it in on the heat cycle!) but found the most useful advice from the
      clicky-keyboards site[6]. I remove all the keys and put them in a bowl of hot
      water containing a scoop of clothes washing detergent. Leave them in for 30
      minutes and most of the grime will be lifted without any scrubbing! You can use
      the detergent solution to scrub the plastics - a rubber-based scrubber/foam
      sponge works very well. If you follow the LK201 and LK401 links at the bottom
      you can see the keyboards in their stripped conditions.

      Anyway, I digress - this particular keyboard had to be completely disassembled
      to get it decently clean, and as a result I had to disconnect the membrane
      conductors from the circuit board.

      LK201 Internal View

      If you look carefully at the top of the connectors into which the membrane
      conductors are inserted you can see that they consist of a tab that presses down
      on each conductive strip. Getting the membranes back into the connectors proved
      a real challenge, as the only way to do it successfully was to lift all the
      connector tabs at once whilst inserting the membrane. In the end I fashioned a
      'lifter' out of the lid of a cat food tin! The membrane connector on the left
      proved tricky as it has to bend through 90 degrees around the RJ socket into
      which the external cable plugs. I'd obviously got this wrong, as when I took the
      keyboard apart and relocated the membrane, put it together again and re-tested
      it there was no longer a problem! Hopefully it will continue to work for a few
      years more.

      Oh, and just to bring a bit of relevance to my inane rantings, look down at your
      keyboard and at the arrangement of the cursor keys. This is called an 'inverted
      T' arrangement and you have the LK201 to thank for that. So, in some small way,
      your keyboard (unless you are using something vintage!) is a direct descendent
      of the LK201 and has the design of VAXtpu to thank for its' layout:

              One feature of this keyboard is its arrangement of cursor
              keys into an inverted-T layout. This arrangement was
              based in part on logging data from the EPT editor. Table
              1 shows the frequencies of transitions between arrow keys
              in the EPT editor.

              The transition from the down-arrow key to the left-arrow
              key occurred more than twice as often as any other
              transition between arrow keys. The inverted T arrangement
              puts these keys next to each other. Three fingers of the
              user's hand can rest on the three most frequently used
              arrow keys. From this position, it is also easier to
              reach up to the up-arrow key than it would be to reach
              down to a down-arrow key[7].

                   LK201 Arrows

      The placement of the keys on your laptop keyboard, however, would appear to
      completely negate the quoted benefits - on the IBM X60 notebook I'm using at the
      moment, for example, their placement at the bottom right of the keyboard and
      where I naturally rest my hands means that there is no easy way for my hand to
      'rest on the three most frequently used arrow keys' except when I specifically
      move my right hand down to the arrow keys. Mind, laptop keyboards are known to
      be ergonomically very bad for you!

      
      ENDNOTES

      1. IBM Model M Keyboard

      2. Gateway 2000 Keyboard

      3. Happy Hacking Keyboard

      4. LK201 Keyboard

      5. LK421 Keyboard

      6. Clicky Keyboards Website

      7. [chi85, Michael Good]
         The Use of Logging Data in the Design of a New Text Editor,
         Proceedings of CHI '85 Human Factors in Computing Systems.