On offer today is a pair of Brimar Red print 12AT7 twin triodes. Carrying good red print, these test as excellentusing my AVO Valve Characteristic Meter VCM163 with the following results: At Va = 250V Vg = -2.0V
U15: Section 1: Ia = 9.5 mA; gm = 5.1 mA/V
U15: Section 2: Ia = 10 mA; gm = 5.1 mA/V
U16: Section 1: Ia = 9.0 mA; gm = 5.1 mA/V
U16: Section 2: Ia = 9.2 mA; gm = 5.2 mA/V
The specification for a new/100% emission valve is:
Ia = 10mA; gm = 5.5mA/V
As you can see, this result show a really strong matched pair of valves with good matching of each triode section within each envelope.