Testing Marconi DEV Valves on AVO Mk3

[David Simpson]

Decided to build a special rig for carefully testing these rare old valves.(See thread currently in "Components & Circuits").
However I've now moved into the realms of AVO Mk3 testing of these end & side-capped wee triodes. Had to build a B4 plug & lead connector. I just set the thumbwheel code to 642300000 & connected everything together. I chose a nominal Vg of -2V, and set the Mk3's switches to give a Va of 40V & a Vf of 2.5V(actually metered at 2.7V ac) - - to get as close as possible to voltages used in 1924. Results were good, and then Vg was varied from -8V down to 0V & Ia readings taken off the Mk3's meter. The resultant plot was pencilled on to yesterday's graph of the 1924 curve & one from my DC lash-up(Not my big LayMarcAvo DC Tester).
So - AVO VCM's can test these early 1920's wee triodes, and probably the earlier V24's(BE's) designed by Captain Round in 1919. I've another 5 DEV valves to test for a BVWS chum on my Mk3.
Isn't valve testing fun on a rainy day ?

Regards, David