The 5642 (European: DY70 (similar)) (P/N 154-0051-00, 154-0079-00) 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, 140 mA).
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, typically a single loop of wire with extra silicone tube insulation.
|Heater||1.25 V, 200 mA|
|Peak inverse voltage||10 kV|
|Peak plate current||5 mA|
|DC plate current||250 μA|
|Min. supply frequency||5 kHz|
|Forward voltage drop||40 V @ 4 mA|