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. The European type DY70 is very similar (with lower heater current).
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.
Tek part number: 154-0051-00, 154-0079-00
|Heater||1.25 V, 200 mA|
|Peak inverse volrage||10 kV|
|Peak plate current||250 μA|