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Tektronix 3B1
10 MHz time base
Tektronix 3B1 front

Compatible with 560-series scopes

Produced from 1962 to (?)


Manuals – Specifications – Links – Pictures

The Tektronix 3B1 is a time-base plug-in introduced in 1962 for 560-series scopes. 10 MHz is is the maximum trigger frequency. The calibrated sweep rates go from 1 s/Div to 500 ns/Div.

There is a switch that enables 5 × horizontal magnification, which makes the fastest sweep 100 ns/Div. The 3B1 has a delayed sweep and a regular sweep.

Key Specifications

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The 3B1 uses vacuum tubes, bipolar junction transistors, and tunnel diodes.

The trigger input goes through the int/ext switch and then the AC/DC coupling switch, and then a 7895 cathode follower. The output of the cathode follower drives one base of a 2N2207 PNP differential amplifier which has a tunnel diode in the collector load. The tunnel diode generates pulses when it switches back and forth between its two stable voltages, which are capacitively coupled to a 2N2501 NPN common emitter amplifier.

The delay pickoff circuit is a 6DJ8 differential amplifier that compares the sweep ramp voltage with a knob-controlled DC voltage which determines the point where the delayed trigger starts. The DC voltage is made by a ZZ1000 80 V reference passed through a potentiometer-variable voltage divider.

When the sweep ramp exceeds the control voltage, a 2.2 mA tunnel diode in the plate load of the differential amplifier switches state.


Some Parts Used in the 3B1

Page Class Description Used in
6DJ8 Vacuum Tube (Double Triode) dual triode 132 502 502A 503 504 515 516 519 529 RM529 533 535 543 544 545 545A 545B 546 547 549 555 556 565 581 581A 585 585A 661 2A60 2A63 3A8 1121 1A4 67 81 82 86 3B1 3B4 1S1 B O W Z Telequipment S32A Telequipment D52 Telequipment S52 Telequipment S51 Telequipment Type A
7895 Vacuum Tube (Triode) Nuvistor triode 3B1 3B3