[Heathkit] TT-1A Tube tester 6EB8 data verification

[Precision Carburetor DP]

Hi Jack.

I don't have any 6EB8 tubes but I have some new 6HF8s.  The 6HF8 is a close
replacement for the 6EB8.  I then tested four new 6HF8s in my TT1A and two
of them tested normally and two had the reaction you had, pinning the GM
meter.  It turns out that the GE brand tubes tested normal and the Raytheon
pinned the meter.  There is something going here but I'm short on time this
week but I will try these tubes and more new tubes in my TV2 Military tester
and post the results.

73s.

Jerry

W2JI  

 

 

 

> I have a recently acquired 6 meter SB-110A with the original 6EB8 tube in 

> the audio circuits.  The original tube tests low (about 40%) for the 

> triode, and I get a 1/4 upscale reading for the pentode before testing for


> the Gm as it warms up, then it pegs the meter upon Gm test.  My first 

> impression is that the triode is low emission, and the pentode is shorted.


> No shorts show up with the usual tests for either section, and reducing 

> the meter setting lowers the pentode peg symptom to on-scale upon the Gm 

> test.  Bias setting has little effect.

> 

> The puzzling thing is that I have tested 4 NOS 6EB8 tubes with the same 

> low readings for the triodes (@ 4), and 2 of the four behave the same way 

> for the pentode section with the previously exhibited passive upscale 

> reading and Gm test meter pegging.  The remaining 2 NOS tubes read 

> normally for the pentode.

> 

> The 6EB8 seems to have the "regular" setup sequence as for other 9-pin - 2


> section triode/pentode tubes normally used with Heath and Collins 

> equipment, but I've never had experience with a 6EB8 before - I believe 

> this is unique to the SB Line in the SB-110/A.  I am using the second tube


> chart update scroll from the early '70s in the tester.   When checking the


> RCA tube manual, it states that the 6GN8 is an "upgraded" 

> (swap/replacement?) tube, yet the TT-1A settings are slightly different. 

> I'd like to use the 6EB8 as original to the SB-110A.

> 

> Can someone with a TT-1A please test a known good 6EB8 and publish the 

> results, or set me straight?  Better yet would be a comparison with 

> another transconductance tester's results with respect to results.

> 

> Thanks  Jack  W3RU