3A74: Difference between revisions
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Tek 3a74 engine analyzer amplifier.jpg|3A74 Engine Analyzer Amplifier | |||
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===Netherlands-made Version=== | ===Netherlands-made Version=== |
Revision as of 10:30, 12 August 2021
Template:Plugin Sidebar 2 The Tektronix Type 3A74 is a four-channel vertical plug-in introduced in 1963 for 560-series scopes. The bandwidth is DC to 2 MHz.
A modified 3A74 MOD 730A (with a charge pre-amplifier on channel 1 to accommodate piezoelectric pressure transducers) was part of the Engine Analyzer package.
Key Specifications
Bandwidth | 2 MHz |
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Input impedance | 1 MΩ // 47 pF |
Deflection | 20 mV/Div to 10 V/Div in 1–2–5 sequence |
Features |
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Internals
Each input signal passes through switchable input attenuators and then into a cathode-follower made from a 7586 Nuvistor triode driving a PNP differential amplifier. The output of this differential amplifier, for each of the four channels, passes through a diode-based analog signal switching network (multiplexer). The output of that multiplexer drives the output amplifier, which is part transistor, part tube. The one-hot select line signals for the multiplexer are generated by a transistor-based ring oscillator, a four-state cyclic state machine. This allows each of the input signals to be traced on the screen, one after another.
The 3A74 uses Tek-made 185 Ω potentiometers in for the VAR GAIN controls. These can be a maintenance issue.
The 3A74 contains a total of eight 7586 Nuvistors.
Links
Pictures
US-made Version
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Front Side
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Rear Side
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Left Side
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Right Side
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Block Diagram
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Channel Switching
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Amplifier
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VAR GAIN potentiometer, sometimes problematic
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3A74 Engine Analyzer Amplifier