Vintage IBM 1403 Printer Problem Evades an Easy Fix

The Computer History Museum in Mountain View has two operational IBM 1401 mainframes, which use IBM 1403 high-speed printers. They aren’t some decades-old notion of “high speed” that barely looks sluggish today, either. These monsters slam out ten lines per second thanks to a rotating chain of type slugs and an array of electromagnetic hammers. Every 11.1 microseconds, a character in the chain would be lined up with a hammer, and if the control circuitry identified it as a character that needed to be printed, the hammer behind the paper would drive the paper into the print ribbon and the slug, putting an imprint of the character onto the paper. When one of these printers failed with a sync error, it kicked off some serious troubleshooting to diagnose the problem.

The IBM 1403’s type chain has a repeating set of characters that spins around at high speed. Unlike a typewriter or label maker, the hammers are not inside this unit. The hammers are on the outside, and work by pressing the paper onto the type slugs as the required characters line up.

Investigation of the problem ultimately led to an intermittent connection in a driver card due to a broken PCB trace, but by then some fuses had been blown as well. In the end the printer was brought back online, but possibly with a slightly damaged coil on one of the hammers.

[Ken]’s writeup on the repair process is highly detailed and walks through the kind of troubleshooting and repairs involved when solving problems with vintage electronics. Electrical fundamentals might be the same, but a deep understanding of not only the architecture but also the failure modes of vintage hardware is needed in order to troubleshoot effectively.

If IBM 1401 mainframes and fixing 1403 printers sounds familiar, it’s because a printer fix has been done before. That was due to a different problem, but still a challenging task to narrow down and fix.

15 thoughts on “Vintage IBM 1403 Printer Problem Evades an Easy Fix

  1. We used to call these column printer so as not to confuse them with line matrix printers.

    Line matrix printers were about 35dB louder lol and about 5 to 10 times the speed. The speed is hard to imagine given that even column printers are pretty fast.

  2. That printer could be fun. If you printed the same character in every position on a line it made a noise like tearing paper. On the other hand printing a line made up of all the characters on the chain in order (I think the order was scrambled for some reason) all the hammers fired at once with a terrible BANG!

    1. lol, The order was scrambles to that you don’t get “a terrible BANG” in normal operation.

      The very large high speed printers: column, line matrix and continuous line often had to bolted to the floor.

  3. This one is a band printer.
    There were drum printers that had a rotating drum. The drum would have 44, 66 or 132 columns of characters. The column would have 64 ASCII characters in each column (ASCII columns 2-5) being upper case only. Each column of characters would be skewed from the adjacent column, so that hammer firing would not occur at the same moment in time. The 44 column versions would have 44 hammers, and it would take 3 drum revolutions to print a complete line of characters on the paper. The paper would shift sideways a character position for each drum rotation. The 66 column version would just shift the paper sideways once. The 132 column version would have 132 hammers and obviously the paper wouldn’t be shifted sideways.
    They were quite noisy, especially when running a test where the same character was printed in all 132 positions on the line.

  4. Used on in Data Processing in High School. Had to keep the idiots in my class from trying to stick their fingers in it to read the output of their code (which at the speed it ran, really? They thought they could do it.)

    New Line loops were always a challenge. Stop the printer before it ran through the whole box of paper.

    1. An ex-Navy guy told me of the sailor that wrote a program that at Midnight on the start of the New Year would print “Happy New Year!”
      (top of form)
      Loop for one minute
      Only the Loop didn’t exit properly and when the sailor was found, he was at one of the clubs- 3 sheets into the wind.
      They drug him back and he eventually was able to halt/remove his program.

      1. That was deliberate, but I’m sure someone else here other than myself has accidentally filled a room with computer printout accidentally with unintended repeated form feed commands. And since these things were fast it didn’t take long for an unattended machine to wreak havoc for operators and amusement for bystanders. :-) Printers…can’t trust ’em must babysit to avoid chaos. :-)

  5. The joys? of the old print train printers. IBM at least enclosed the ones I worked with. Even the later models like the 6262 print band printers had fully enclosed cabinets. Tandem OTOH, had a rotating print drum and a partial plastic enclosure…AKA The Anvil Chorus when it printed.

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