13D9, Brimar, Large Font, Special Quality 12AT7, ECC81, Footscray May 1964 Production

13D9, Brimar, Large Font, Special Quality 12AT7, ECC81,  Footscray May 1964 Production

On offer today is a lovely Brimar 13D9, a premium quality ECC81 carrying the date code for May 1964.       Carrying good white print, it tests as excellent using my AVO Valve Characteristic Meter VCM163 with the following results: At Va = 250V Vg = -2.0V 

Section 1: Ia = 13 mA; gm = 4 mA/V

Section 2: Ia = 12 mA; gm = 4.7 mA/V

The specification for a new/100% emission valve is:

Ia = 10 mA; gm = 5.5 mA/V

As you can see, this result show a strong valve with excellent matching of each triode section within the envelope.