[Heathkit] Testing 6BN8 tubes on a TT-1A

[jack m]

Has anyone else observed that most 6BN8 Triode sections don't test very high using the selector settings in the Heath charts?  Most NOS NIB tubes I test of this type are "slow" and very few meet the 810 mmho reading (most go about halfway), while the two diodes always seem to test good.  This is true for both of my TT-1A's.  The tubes always seem to work in their circuits very well, however.  I do not have a Hickock or TV-7 to compare. 
 
I never use the current limiting filament settings - just the straight 6.3 volts.
 
Thanks for any feedback.
 
Jack  W3RU