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An 8-tube module from a 1954 IBM mainframe examined
By Thom Holwerda on 2018-01-08 13:32:00

IBM's vacuum tube computers of the 1950s were built from pluggable modules, each holding eight tubes and the associated components. I recently came across one of these modules so I studied its circuitry. This particular module implements five contact debouncing circuits, used to clean up input from a key or relay. When you press a key, the metal contacts tend to bounce a bit before closing, so you end up with multiple open/closed signals, rather than a nice, clean signal. The signal needs to be "debounced" to remove the extra transitions before being processed by a computer.

This is so far before my time, it basically looks like 19th century machinery to me. The steps between this module and what we have today blow my mind.

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Thanks a lot for this one, Thom.
By dionicio on 2018-01-08 15:51:48
Lovely Handcraft-ship. Harmonic Resonance was key to keeping error control within USABLE purposes.

As Natural frequency of tubes deteriorated quite quickly -and resistors being the cheaper of the set- they became the jokers attempting to extract a little more of useful life.

Every week started by checking how trust-able those modules remained.

Nowadays, resilience and productivity wise, them were a huge advance from former electro-mechanical relay logic circuits.

Those Men And WOMEN were Engineers in all the sense. Untamed admiration.

HARDWARE people.

Quite ad-hoc at these times of sensing the soft floor of systems theory.

Edit: electro-.

Edited 2018-01-08 15:56 UTC
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IBM being the natural...
By dionicio on 2018-01-08 16:16:37
Their business machines, input and output hardware, stats and census tasks, algorithms already there.

Their clients, also.

First electronic modules plausibly just replaced electro-mechanical ones.

All this fuss just to point on the non-revolutionary aspect of GOOD engineering.
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On Academic Reasons...
By dionicio on 2018-01-08 17:05:01
Logic Modules Like This Can Be replicated with high pressure halogen tubes and solid state capacitors. Lowering electron emission temp. Neon lights, or displays.

Noting from photos that tube refrigeration was diverged (in its way up) from other components. This air was probably more ionized, also.

Is it 5bit logic?
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CuriousMarc's youtube channel
By wigry on 2018-01-08 17:36:19
Been following the CuriousMarc's youtube channel for a while now and the appointed video appeared there recently. So if you like more stuff like this then the channel is for you.

Also the latest videos as of date are about magnificient HP terminals using 9-bit (yes thats nine) ROM's for character memory and mindblowingly cool way to create antialising to get very smooth text on a simple monitor.

The linked blog seems to be a parallel world to the youtube channels - same content different people. Just a bunch f guys doing cool stuff. One records in the video, another one writes blog posts

Edited 2018-01-08 17:39 UTC
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By bbjimmy on 2018-01-08 20:43:59
This stuff reminds me of my first project in Electronics class in high school. We made a one tube am radio. Mine kept blowing up the tube. My lab partner's only job was to get the pin assignments for the tube. he came back with the Metal Tube , MT assignments and all we had was the Glass Tube, GT version of the amplifier. needless to say, I got a different lab partner after exploding many glass tubes.
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Comment by quatermass
By quatermass on 2018-01-08 22:48:39
Yes, when the first 'home' computers came out, quite a few didn't have any key debounce builtin.

Back in the Eighties they had to update the OS involved to get the keyboard working.

Seems pretty basic now, but this obvious step eluded the manufacturers.

Oh we had lots of very primitive problems like this in the late Seventies, early Eighties.

Lots of engineers, no actual testers.... :)
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More than debounce?
By Iapx432 on 2018-01-09 15:08:48
8 tubes to debounce seems excessive. This must have been a buffer or a latch as well.
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