5 pin tube tester

Viridian,
Unless they have radically changed the design, the Tube Research GT 400 still uses OD3 tubes.

I still have some spare OD3's around here from when I owned that amp.

Viridian,

The tube in questions was a " OD3W " Although I did notice a few OD3 in the pile as well. But these tubes are not the same. For what it's worth the OD3 is also employed in the new BottleHead pre III.

There a few amps that use a 0D3, and even though an 0D3 and a 0D3W look very different they are substitutes. The W just has that protective shock absorber shield around it. It can be tested with the same settings as the non W.

It is very difficult (impossible?) to identify a tube that has no markings. There were 10's of thousands of different tubes made so going just on looks is pretty much impossible.

Are there any marks at all?

The 0D3W is fairly common and doesn't demand a very high price so purchasing a tester just for it would probably lose you some money unles you have a lot of them.

Herman,

Some tubes have marks but most of what is in question has nothing. These look to be of the pre amp type.

I have many large tubes thought that I can read the numbers but am not able to test on my tester. But for now I will wait until I decide if I'm going to pursue the tube quest further. I orginally bought this mess of tubes becuase of a couple that I wanted. They came very cheap. Some of these are really cool looking. To bad I can't find a use for them.