This is a basic primer on buying used or new tubes from sellers that know nothing about the tubes they are offering. Also offers simple tests that any person can conduct to determine the quality of a vacuum tube.
When you look for a vacuum tube, whether it be a receiving tube or transmitting transmitter or amplifier tube, there are some basic questions you would ask the seller to determine the quality. This is assumeing the seller knows about the item there selling which is sometimes but not always the case.
First question to ask is, does the filament have continuity. This may be checked by any ohm meter or continuity checker. Place the checker accross the filament terminals and if the continuity lites up or the ohm meter indicates a readable resistance, the filament is good. The resistance should be very low maybe one tenth of an ohm or as much as 2-5 ohms reading on the meter.
Second, is there any connection or continuity between the filament and the other elements of the tube such as between the grid or plate cap and the filament. If so the tube is no longer usable as a tube.
Third, are there any loose particules inside the tube that may indicate broken grid or filament elements. If there is, the tube is no longer usable as a tube but if the tube is large enough, you might consider making it into a table lamp. There should be nothing loose inside the tube.
Fourth, what color is the glass. Is it very brown or clear. If it is dark and dirty looking this usually indicates the tube is well used. This applies primarly to transmitting type tubes.
Five, does the inside of the glass look clear and are there any cracks in the glass. If there is a white milkyness inside the tube or there are obvious cracks, this indicates the tube has lost its vacuum and is useless as a tube.
And last, is the tube new or used. If you see multiple even spaced marks on the outside of metal-ceramic tubes , even if the appears new, this indicates it has been in a tube socket and is probably used and not new. Also, have the seller the pins to see if there are marks on them. Another indication the tubes were in tube sockets. Silver plated ceramic tubes clean very well with jewelrey cleaner and its hard to tell by looking at the posted pictures as to there newness. You will have to ask the seller for some specific answers regarding marks on the metal parts to determine whether the tube is new or used. I along with other tube sellers offer both new and used tubes and sometimes its hard to determine when I purchase tubes for resale as to whether there new or used. If they test well on the tube tester and you have the origianl boxes, its a good bet there new but now always. If they test well, this is the most important aspect of quality. I hope this helps you in buying new or used tubes.
Thank you and good hunting from "unclegeorges"