From TekWiki
Jump to navigation Jump to search
Manuals – Specifications – Links – Pictures

The Tektronix Type 3B3 is sweep unit (time base) introduced in 1963, intended for use with the 561A. It works fine in other 560-series scopes.

It provides a calibrated delay from 500 ns to 10 s after the trigger event, before sweeping. Delayed sweep allows the operator to "zoom in" on regions of interest in a waveform.

The 3B3 provides an intensified mode that indicates the selected region of interest in the delayed sweep by showing the entire waveform with the trace brighter in the selected region.


please add


Triggering is done using a 2 mA germanium tunnel diode, a 1N3714. The trigger source is buffered by a 7895 Nuvistor triode cathode-follower driving a differential amplifier formed by two 2N2207 germanium PNP transistors. The collector current switches the tunnel diode when a triggering event occurs.

Up to serial number 1029, the 3B3 uses Transitron T12G germanium diodes (equivalent to the 1N270) to protect the transistors of the front-end differential amplifier. Starting at serial number 1030, silicon diodes were used for that function.


Some Parts Used in the 3B3

Page Class Description Used in
7895 Vacuum Tube (Triode) Nuvistor triode 3B1 3B3