A Simple, Valve Curve Plotter

[Alan Douglas]

 it waxes lyrical about over current but being variable it doesn't say anything about over voltage.

That brings to mind an HT supply I have used for curve tracing, 0 - 550V (as I recall) set by panel switches. Easy to step the anode voltage by exactly 50V and plot a curve each time.  

Now Fluke made lovely supplies like this, and I have two, but this one was made by some company I never heard of, in Rahway, New Jersey, a town better known for stinky oil refineries.  It works beautifully, unless the mains power is interrupted, in which case it comes back on at full voltage!  I fixed it by installing a time-delay relay so it would not come back on after a dropout.  I never did smoke any rare valve before I discovered the quirk, but I might have.