Indicator tubes for transistor logic machines.

William Donzelli wdonzelli at
Sat Nov 10 19:56:29 CST 2007

> When I was *much*  younger, I used to run into them occasionally.
> The BED coding made no practical sense to me.  DEB would have made
> more sense, allowing one to recognize the multiplier with a glance,
> instead of grabbing the resistor and maniuplating it to see if what
> you have is a 470 or 47K ohm reisstor.  When these things were
> soldered tightly to mounting strips in military equipment, it could
> get to be downright frustrating.

It should be noted that BED resistors were almost never used by the US
military. The exception was during a few years in the 1930s, and only
in a few pieces of equipment. By 1940, the US military had gone
completely with the stripe system.

> Another one to confuse-a-boss would be 6-dot mica capacitor color
> code (one could find these on 1960's computer equipment).  I probably
> still have a few of these in operation.

It should also be noted that there never was a universally adopted
color code scheme for capacitors. The RMA tried for many years to get
the manufacturers to adhere to the standards, but were very
unsuccessful. The best scheme when dealing with these is to look for
the two dots that make sense as the value, and see if the next, often
around the corner, is a valid multiplier color.

While not a common occurence, I have seen the color coded "postage
stamp" caps on IBM SMS cards from the 1960 era.


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