Friday, October 5, 2012


In honor of Tam's link from a post showing examples of logic elements from early computers, here's a link to a site showing a nice dual-triode flip-flop as used in the Burroughs 205. (Plus actual pictures of actual hardware.)  Enough of those and you'd have yourself some memory; also an air-conditioning challenge.  But wouldn't it be fun? 


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  2. Those were the days when a machine didn't even flinch at static electricity, but a train speeding by could cause all manner of errors.

    I was researching an answer for a technical question posed to Byte Magazine some years ago (they had a stable of nerds who answered technical letters - it was my first published work) and came across a guy who ran a computer store in Columbus, Ohio, who'd been around a while. Before he'd answer my question, I had to answer his. He said, "Back in the days when computers used tubes, most technicians carried a wooden pencil with a pink pearl eraser on the end in their tool kits. What was it for? Here's a hint: it wasn't for cleaning contacts."

    I was able to answer correctly. It was to test for microphonic tubes by tapping them with the eraser. Some of those miniature dual triode tubes had loose grids, and they'd pick up vibration and amplify it.

    My old Drake TR3 had one of those tubes in the audio chain. My cat jumped up on top of it one day while I was using it with headphones and nearly blew me out of my chair.

  3. I'm on of the few that has worked with logic using tubes. It's interesting and mighty different from
    that using transistors or Integrated style logic on silicon.

    My favorite was Beckman EPUT meter, EPUT is Events per Unit time, usually called frequency counter now.
    A handful (60 to be exact) of 12AT7s in ring counters for the 1 of 10 coutners/displays and a real
    divide by two flip flop followed by a divide by 5 ring counter to prescale the input. It could count to 5mhz per spec and 10megacycles (was then) on a good day. Gobs of fun to keep working.