3A74: Difference between revisions
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* [[Media:Tek 3a74 cal outline.pdf|Tektronix 3A74 Calibration Outline (PDF, OCR)]] | * [[Media:Tek 3a74 cal outline.pdf|Tektronix 3A74 Calibration Outline (PDF, OCR)]] | ||
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The '''Tektronix | The '''Tektronix 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. | 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. | ||
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==Pictures== | ==Pictures== | ||
'''US-Made Version''' | |||
<gallery> | <gallery> | ||
Tek_3A74_front.jpg | Tek_3A74_front.jpg | ||
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Tek 3a74 engine analyzer amplifier.jpg|3A74 Engine Analyzer Amplifier | Tek 3a74 engine analyzer amplifier.jpg|3A74 Engine Analyzer Amplifier | ||
</gallery> | </gallery> | ||
'''Netherlands-Made Version''' | |||
<gallery> | <gallery> | ||
Tek 3a74 nl1.jpg | Tek 3a74 nl1.jpg |
Revision as of 23:56, 28 November 2023
The Tektronix 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
Netherlands-Made Version
Some Parts Used in the 3A74
Part | Part Number(s) | Class | Description | Used in |
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6CL6 | 154-031 • 154-0031-00 • 154-0286-00 | Vacuum Tube (Pentode) | 7.5 W power pentode | 132 • 310 • 310A • 316 • 317 • 515 • 524 • 525 • 531 • 535 • 535A • 545 • 545A • 545B • 549 • 570 • 581 • 581A • 585 • 585A • 3A74 |
7586 | 154-0306-00 | Vacuum Tube (Triode) | Nuvistor triode | M • 1A1 • 1A2 • 1A5 • 10A2 • 10A2A • 11B1 • 11B2A • 321 • 321A • 3A1 • 3A1S • 3A3 • 3A5 • 3A6 • 3A7 • 3A8 • 3A74 • 3S76 • 3T77 • 3T77A • 3B5 • 4S1 • 4S2 • 6R1 • 6R1A • 9A1 • 9A2 • 82 • 86 • S-311 |