I would like to build a set up for testing transmitting tubes. I was
thinking of just testing a couple of points. My power supply will have a
capability of 500 volts maximum at 2 amps. I would test a triode for
instance for cutoff and then I was thinking of going to the plate
dissapation value. I would do this short term so that the tube would not
need to have forced air cooling.

I am planning to sell some of my transmitting tubes and would like to
advertise them as having passed a series of tests. What tests would be
most meaningful?
=====================
If the valves are old a Hipot test would be very important to check for
'gassing'.
A Hipot or breakdown test involves a very high voltage up to 10000 V or
higher and a very low current in the few microamperes region.
Real transmitting tubes (used for amateur radio power amplifiers) operate at
anode voltages somewhat higher than 500 V , usually between 2000 and 4000 V.
TV line sweep tubes often used for RF Power amps in the sub kW range usually
need up to 1250 V anode voltage.

In addition to an anode voltage supply ,you need an adjustable up to - 250 V
grid bias supply (a few mAs) . Your 500 V supply will be adequate for a
screen supply when testing tetrodes and penthodes, be it that the max
current would probably not exceed 25 mA.

Frank GM0CSZ / KN6WH