Is there some simple way to test a valve to see if it is go/no go?

The best way is with a valve tester though most of us don't enjoy the privilege of owning such a beast so the next best thing is to try the valve in a receiver known to work. The only catch here is that you need a radio that is designed to operate with the valve you want to test.

If you have the pin-out diagram, you can use an ohmmeter to test the basics: for filament continuity (good) and for inter-electrode shorts (bad) -- note electrodes on some valves are connected internally, as per the applicable diagram.

Valve performance can really only be measured to some extent with a mutual conductance tester but, as they say, the best performance tester is the circuit itself with all of the correct voltage applied to the electrodes -- once you have determined that there are no internal shorts.

Is there anything to look for that indicates a bad valve? I'm looking at one now its a Milli watt 3V4, its got a silver coating inside so that you cant see inside of it,would it be burnt out or is this normal for that type of valve? I can see I have a lot to learn about valves and their circuits.

Many have been fooled by the black or silver coating. Only when it turns to white, like talc, is there a visible indication that it might have air in it.

The silver stuff is "getter" which is often magnesium, used to get rid of any remaining air etc. the is left within the envelope.

3V4 is a 7pin valve pins 1& 7 are the 2.8V filament and it is centre tapped at pin 5 for 1.4V (read clock wise looking at the base of the removed valve). There should be no continuity between these pins and any of the others.

Keep fingers off, at least one, of the ohmeter probes.

Do not use a 1.5V cell to see if you can see the filament glow and don't drop it: place it.

And as GTC wrote. That only tests the filament & bad shorts.

Marc

Back again! Thanks for explaining that for me,Ive only got about a million of em. (questions) LOL