The 12BH7A-STR is a modern variant on the original 1950s design of double triode. Originally the valve was designed for use in television vertical deflection stages as well as a Class A voltage amplifier.
The A variant of the 12BH7 has a defined warm-up time of 11 seconds.
The anode boxes are larger than typical double triodes due to the requirements of vertical deflection systems with high peak voltages and currents. The heater is correspondingly more substantial being twice the heater power of most other double triodes.
A closer view of the electrodes.
The anodes are stitched together along the centre line between the two halves and a rectangular cross section of working space results.
The thin glass tube envelope is 22 mm in diameter, and excluding the B9A base pins is 61 mm tall.
