Indicator tubes for transistor logic machines.
jrr at flippers.com
Sun Oct 28 20:25:36 CDT 2007
Tony Duell wrote:
>> Is anyone familiar with vacuum tube indicators used on transistor logic
>> Several modules have some sort of visual indicator tube as well.
>> These tubes are not much larger than a standard NE-2 bulb, but they more
>> resemble subminiature vacuum tubes.
>> The tubes are marked 01037 J3, each had four leads. Two of these leads
>> shows a resistance of 9.8 Ohms, and
>> appears to be a low voltage filament. One is grounded, the other is
>> connected to a bus in the rack of logic.
>> There is no 'getter flash' inside the glass tube, so they may be some sort
>> of glow discharge tube.
>> Looking at the insides of each tube thee appears to be a very fine V style
>> filament and a grid-like structure, but
>> I see no clear anode or plate structures. There are two thin 'wires'
>> outside of the grid, one in front and one
>> behind the central grid-like / filament structure.
> These sound a lot like what we caleld 'DM160's in the UK. These are about
> the size of a 1.24" (3AG??) cartridge fuse and have 4 active leads coming
> out of one end.
> 2 of them are a filament (direcctly heated cathode), running at about 1V.
> Another is the anode/target, which IIRC has a grid-like structure, It is
> normally riun at about 30V +ve wrt the filament. The fourth wire is the
> control grid, IIRC with the grid at the smae voltage as the filament the
> device glows green, a -3V grid bias cuts it off and it's dark. Needless
> to say the actual current drawn y the cotnrol grid from the transistor
> logic is minimal/
Nice picture of a machine using the DM160s:
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