[R-390] Tube testers

[Tim Shoppa]

W2DBO wrote:
> of em, they all tested good, took the rx outa the
> cabanit and grabed the voltmeter and check all plate
> and screen voltage everything looked good, worked
> on that radio for 3 days, the 4th day my Pop came up
> to me and handed me a box with a 12BE6 and said put
> this in and I said I had checked all the tubes and their
> are all good, I put the tube in and 45 seconds later
> it was playing

Seeing how the 12BE6 is a heptode and in a AA5 used
as both an oscillator and a mixer, not too surprising that
the tester got stumped by it :-).

Most likely it wasn't oscillating and the tester used
a grid not for oscillation for its test!

I was recently working on SPICE models for heptodes
and no tube book gives useful information for modeling.
Had to do some 3-dimensional curve tracing!

Tim.