3B4
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The Tektronix Type 3B4 is a single-timebase plug-in for 560-series scopes, introduced in 1964.
It was intended primarily for use with the 561A, but works fine in other 560-series scopes. The 3B4 is unusual in having an explicit "FREE RUN" mode.
In the triggered modes, the tunnel diode-based triggering is rated to work to 20 MHz. The vertical bandwidth of typical 560-series (non-sampling) scopes is about 10 MHz, so 20 MHz is adequate.
Key Specifications
| Sweep | 50 ns/div to 5 s/div, 1–2–5, variable to ×2.5; 5-step magnifier up to ×50 |
|---|---|
| Trigger | DC to 20 MHz, internal 0.1 div / external 0.5 V |
| X input | 200 mv/div to 5 V/div in 5 steps, variable to 12.5 V/div into 1 MΩ // 20 pF (max. ±20 V), bandwidth 400 kHz |
| Features | Single Sweep, X input, free-run mode |
Links
Internals
Triggering is done with a TD3A/1N3717 4.7 mA tunnel diode. The trigger input is amplified and buffered by a 6DJ8-based differential amplifier driving a common-emitter 2N964 germanium PNP transistor whose collector current switches the tunnel diode.
Pictures
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Front View
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Left Side View
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Right Side View
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Top View
