The 5642 is a directly-heated high-voltage rectifier tube. It has three flexible lead connections and is intended to be soldered into the circuit.
- filament volatage = 1.25 V
- filament current = 200 mA
- peak inverse volrage = 10 kV
- peak plate current = 250 μA
It is used in the CRT cathode and post-deflection acceleration supplies in many Tektronix scopes. In typical CRT circuits, the filament/cathode leads of each 5642 have their own secondary winding on the HV transformer.