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Reply with quote  #1 
I have a Precision Apparatus Company Series 920 tube tester. I was trying to find out how to test 300B tubes on it as they are not on the settings roll of the tester. I came across an interesting website that explained why the 300B is not included on some testers ( 

I will probably get Bruce's book and build either the tube tester or analyzer instead.

Reply with quote  #2 
There are very few vintage tube testers from the 1950s on that would test a 300B.  This based on all the tube testers I have studied trying to find ones that would test a 300B.

Having said that you can try this:

See if your tester has the tube socket for a 4-pin tube such as the 300B.   Which is the same socket a 2A3 uses.

There are vintage tube testers that although will not list a 300B as a tube that can be tested, will list a 2A3.  I do not know off the top of my head if Precision Tube Testers fit this category.

If so, then see if it has test settings for a 2A3.  

If so, adjust filament voltage from 2.5 volts for the 2A3 up to 5 volts for the 300B and leave the other settings from your tube test data/settings for the 2A3 the same on your tube tester, and then test. 

The 2A3 and 300B are very close in performance, with the filament voltage being the main difference, such that the result given by doing this should tell you at a minimum whether or not you have a good or bad 300B.

Other than that the TS tube tester is probably your best bet.  It certainly is on my "to do list" not just for the 300B but for the EL-509 and the other Russian tubes used in TS designs such as the 6C45 in the Phono Pre and 6H30s in the Mini.
Reply with quote  #3 
I tested my 300B tubes using your suggestions. It worked very well and so I am going to do some preventative maintenance on the 920 Series tester by changing out the old caps.

Waiting for my copy of "Tubes and Circuits" to arrive in the mail and will check out the tube tester.

Thanks for the advice!

Reply with quote  #4 

I know a little late to the party, about the W.E. 300B testing But I was looking for setting for a 2A3 and came across this forum! 

We have an older Precision Apparatus 920 with many older tube chart sheets (all older) that did not have setting for the 2A3

However our supplementary tube charts do have the settings for the 300B

Possibly to help someone else for future reference

On a Precision Apparatus 920 settings:
for a 300B are A-3, B-5, C-40, D-4, E-1, F-1, Press B

Peter Romano
Reply with quote  #5 
as i follow this subject; Tube tester, at this stage i would imagine there are MANY that know and or have a Stand-Alone tester for the tubes required in all of the Transcendent Products.With that, is there a SPECIFIC TESTER Set-up that all use?
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