• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

vacuum tube logic gate


2006-08-08 6:04 pm
-Will this schematic work for an AND gate using a 6F1P tube?

~Tube info: http://russiantubes.com/prop.php?t=12&p=353
~Tube charact.:

-How should I change it?

-Would 5VDC logic voltage work?

-Do I need to isolate the output or just connect it to a resistor+led?

To answer your question, I was doing it for a project demonstrating how transistor and tube logic gates worked for a class project.

Thanks in advance.

There is a great deal of discussion of this sort of stuff on the neonixie-l Yahoo!!!!! group. We like to build clocks with nixies & preferably vacuum-based logic - thyratrons are popular, but there are some there that have built scary scary stuff:

Wonderful tube clock

This is in German, but Google & Yahoo language tools both do a fair (and amusing) job of translation.

Lots to be learnt from there...

Heres a good presentation

another thing, if I made something like this

What aproximate values should I use and is V1\V3 (in the picture) the amount of voltage?

Heres a good little presentation that gives you the voltage if you scroll down. Although I don't think it is for your specific tube, I thought it would help.
For suitable logic levels, you can make any magnitude-counting logic gate. That is:
- NAND changes state when the number of active inputs is maximal (N active = M total)
- NOR changes state when active inputs is >= 1 (regardless of M)
- You could define other (symmetrical) >2 input gates for inbetween cases, e.g., output changes when >= 2 inputs are active, etc.

You don't need to use parallel devices (like the first link's NOR gate), you can simply connect the grid to the voltage divider(s) from proceeding stages. The grid voltage resulting from multiple dividers connected in this way will be, for example:
Source 1 = 50V, Source 2 = 50V: grid voltage -8V ("off", so output will be "high")
Source 1 = 50V, Source 2 = 100V (or 100 and 50, respectively -- same result): grid voltage +2 ("on", so output will be "low")
Source 1 = 100V, Source 2 = 100V: grid voltage +12* ("on", so output will be "low")

*Of course, the grid will conduct; this would only be the voltage without a grid connected to the voltage divider. The consequence of grid current is lower saturation voltage (particularly for a triode), which should be designed for minimal effect.

As for voltages and values: grid resistors around 100k, and plate resistors around 10k, will be quite reasonable with most types. Plate supply 100-200V should be plenty, and you'll need a similar negative supply for grid bias. The plate resistors can be much smaller than in typical audio applications, because the voltage gain needed is not very high: in the above example, a maximum 20Vpp swing went from "off" to "on". With the gain reduction due to cutoff and saturation, and due to using the grid voltage dividers, you still only need a gain of 10 or so.

Unless you can find a project where someone's used tube logic already, you'll have to go to the drawing board and use the plate curves to come up with the correct values.



2008-03-12 9:59 pm
Somebody resurrected this thread from long ago ... anyway ...

in practise logic gates in actual commercial vacuum tube computers were usually done with "crystal diodes" followed by a tube inverter

well, at least starting in 1953 as documented on page A13 ff (of 400) in the "IBM 700 Series Component Circuits Manual", a very detailed and thorough reading for anyone interested in this subject ...

it can be found here: IBM 700 Series Component Circuits Manual
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