To date, I have just placed a replacement tube into the socket in the same orientation as the old one but how does one determine the orientation otherwise? Thanks!
Robert J
Favorite Answer
Yes, they need to be in the correct orientation - but the bases are not symmetrical, you cannot really get it wrong.
Smaller valves (tubes) in eg. B7G or B9A bases have a gap in the pins.
https://www.cricklewoodelectronics.com/images/D/B9Aed3.png
Larger ones like Octal have a key on the centre spigot.
http://www.abeltronics.co.uk/images/pictures/vac4.jpg
Some older styles have an irregular pin arrangement or some large and some small pins, so again they only fit in one orientation.
http://www.tubecollector.org/documents/bases/diag5.gif
Anonymous
Hi so they are designed to only go in the socket one way. there is a lot of myths about vacuum tubes and a lot of rubbish. so if it was a used one chances are it might not be any better than the one it replaced. the issue is about how they are internally constructed as the cathode is doped with negative electrons these get stripped off as it us used.
as this fact seems to be ignored. the result is a vacuum tube or what we brits call valves,. is they no longer work.
Daniel K
Robert is right. Vacuum tubes can only be inserted into the socket one way by design. You would have to use a really stupid amount of force to insert one the wrong way and you would probably break either the tube or the socket.