3B1
The Tektronix 3B1 is a time-base plug-in introduced in 1962 for 560-series scopes. It is compatible with all the members of the 560 scope family other than the 560 itself.
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
| Trigger Frequency | DC to 10 MHz |
|---|---|
| Sweep Speeds | 1 Sec/div to 0.5 μs/div in 20 1-2-5 steps |
| Sweep Types | Normal and Delayed |
| Sweep Magnification | x5 |
Internals
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.
Pictures
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3B1 Front
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3B1 Left
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3B1 Right
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3B1 Bottom
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3B1 Top
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3B1 In 1965 Catalog
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3B1 Normal Trigger Circuit
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3B1 Delayed Trigger Circuit
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3B1 Delay Pickoff Circuit
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3B1 Normal Sweep Circuit
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3B1 Delayed Sweep Circuit
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3B1 Horizontal Amplifier Circuit
