My Very First Computer

USS San Juan (CL-54): Crewmen at general quart...

USS San Juan (CL-54): Crewmen at general quarters, while the ship was at sea, circa 1942. View looks aft from the after superstructure. Note flash-protection clothing worn by the men, 1.1″ quadruple anti-aircraft machine gun mount in left center, 5″/38 guns beyond, and depth charges on “K-gun” throwers by the main deck edge. (Photo credit: Wikipedia)

I made a fine living and career as a computer software geek (a programmer) for close to 40 years. But take a look at my very first computer which I took partial possession of when I was a mere lad of 20 years old.


This is the MK1A Fire Control computer – my very first computer. As you can see it was a deck top computer, but quickly converted to a lap top when three of us sailors bellied our laps up to the machine during general quarters. My station was the one on the left side.


This is what it looked like inside with the covers removed – gears, integrators, wires, servos etc. etc. It never broke down which is a good thing, because none of us had any idea as to how to fix it.


The section with the red knobs was my section – the gun elevation controls. The switch panel connected the computer to the gun mounts and put them into various operating modes – auto, manual, autonomous etc.


As you can see the MK1A was one of the very first computers to use touch controls. Spotters on shore or from aircraft called in coordinates and we would crank them into the computer.

The computer was connected to the MK37 Gun Director which could lock on to a target  and control my matched set of 5 –  5”38 caliber guns.


Not me, but could have been.


This is the “stable platform” a gyroscope which enabled the guns to track solidly regardless of the sea state. It sat right next to the MK1A and yes, those are the gun triggers on the front.


Two of the matched set of 5 – 5 inchers. I also worked in the gun mount as well as the magazines directly below the mount – not a good place to be when under enemy fire.


And here is the result of our work.

Sometimes – in spite of all that modern computer technology we just got it wrong somehow. A bad batch of ammo cooked off in the barrels and did this to three of our 5 guns. Thank God no one was hurt.


A “tin can” at Pearl Harbor.

Hope you enjoyed this tour through the weaponry of a Fletcher class tin can.

Some additional interesting pictures of life on a “tin can.”

Don Johnson – November 2013


2 responses to “My Very First Computer

  1. Those were the days…..gee, I miss selsyns, amplidynes, ee8 field phones MPN-1’s and APS42’s…..on second thought maybe these are the days!

    • Gosh Ed … don’t know what those things were: selsyns, amplidynes, ee8 field phones MPN-1′s and APS42′s Fill me in, and tell me a little about yourself as well at ‘’ Always good to hear from you.

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