Tested with L3-3 tubetester at Ua=100V, Ug1=-1.5V, Uf=6.3Vdc

Results:

1. t1 Ia=12.2mA ; S= 11.4mA/V

    t2 Ia=13.4mA ; S= 11.4mA/V

2.          14.6             12.0

             12.8             11.6