3A74: Difference between revisions

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title=Tektronix 3A74|
title=Tektronix 3A74|
summary=2 MHz four channel vertical amp|
summary=2 MHz four channel vertical amp|
image=tek-3a74-front.jpg |  
image=Tek_3A74_front_crop.jpg |  
caption=3A74 front|
caption=3A74 front|
introduced=1962 |
introduced=1962 |
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==Pictures==
==Pictures==
<gallery>
<gallery>
Tek_3A74_front.jpg
Tek 3a74 1.JPG|Front Side
Tek 3a74 1.JPG|Front Side
Tek 3a74 2.JPG|Rear Side
Tek 3a74 2.JPG|Rear Side

Revision as of 10:20, 12 December 2018

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
Input impedance 1 MΩ // 47 pF
Deflection 20 mV/Div to 10 V/Div in 1–2–5 sequence
Features
  • Invert switch per channel

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