View source for 3B1

{{Plugin Sidebar
|manufacturer=Tektronix
|series=560-series scopes
|type= 3B1
|summary=10 MHz time base plug-in
|image=Tek 3b1 front.jpeg 
|caption=Tektronix 3B1
|introduced=1962
|discontinued=(?)
|designers=
|manuals=
* [[Media:070-344.pdf|Tektronix 3B1 Manual]]
* [[Media:070-449.pdf|Tektronix 3B1 Performance Check Out]]
* [[Media:050-0582-00-TEK_3B1-3B3-MOD.pdf|050-0582-00 Germanium Transistor Replacement]]
}}
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.  

{{BeginSpecs}}
{{Spec | Trigger Frequency | DC to 10 MHz}}
{{Spec | Sweep Speeds | 1 Sec/div to  0.5  μs/div in 20 1-2-5 steps}}
{{Spec | Sweep Types | Normal and Delayed}}
{{Spec | Sweep Magnification | x5}}
{{EndSpecs}}

==Links==
{{Documents|Link=3B1}}

==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==
<gallery>
3b1 front.jpg|3B1 Front 
3b1 left.jpg|3B1 Left
3b1 right.jpg|3B1 Right
3b1 bottom.jpg|3B1 Bottom
3b1 top.jpg|3B1 Top
3b1 cat3.jpg|3B1 In 1965 Catalog
3b1 normal trigger.png|3B1 Normal Trigger Circuit
3b1 delayed trigger.png|3B1 Delayed Trigger Circuit
3b1 delay pickoff.png|3B1 Delay Pickoff Circuit
3b1 normal sweep.png|3B1 Normal Sweep Circuit
3b1 delayed sweep.png|3B1 Delayed Sweep Circuit
3b1 horizontal amp.png|3B1 Horizontal Amplifier Circuit
</gallery>

==Components==
{{Parts|3B1}}

[[Category:560 series plugins]]