Indicator tubes for transistor logic machines.

John Robertson jrr at
Sun Oct 28 20:25:36 CDT 2007

Tony Duell wrote:
>> Is anyone familiar with vacuum tube indicators used on transistor logic 
>> machines?
>> ...
>> 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/
> -tony
Nice picture of a machine using the DM160s:

John :-#)#

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