This exhibit was an ebay find and has no markings. The four pin base is American and designed to fit a bayonet socket. The valve is clearly a directly heated triode. The marks on the envelope are internal.If it is American in origin it would be reasonable to use their phrase 'whatisitatron' to describe this valve.![](../pics/aaa1286a.jpg)
The folded bright sheet anode is pressed to have side flanges that both connect to the support rods and also increase the radiating surface area.![](../pics/aaa1286b.jpg)
The inner marks look like a failed getter. The top connection, above the anode, is the filament top support. Looking into the top of the anode reveals a broken filament and the upper grid wires have turned blue, probably through being overrun.![](../pics/aaa1286c.jpg)
The grid is held between two supports.The balloon envelope is 44 mm in diameter, and excluding the base pins is 106 mm tall.Reference: Observation. |
Updated April 17, 2013.
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