The 7189A (P/N 154-0503-00) is a power pentode tube with a B9A (Noval) miniature 9-pin base.
The 7189A is the higher voltage and power version of the 6BQ5/EL84 and 7189/E84L vacuum tubes. It can handle 400 volts on the screen and 440 volts on the plate. Its maximum screen dissipation is 2.2 W, and the maximum plate dissipation is 13.2 W.
Note that the pinout of the 7189A is different from the 7189 - the screen grid is additionally connected to pin 6, and the control grid additionally to pin 1 (for better heat dissipation). To use a 7189 in place of a 7189A in the Tektronix 106, the socket needs to be rewired.
GE was the only US maker of the 7189A.
- Four 7189As are used in the output stage of the 106.