3A74: Difference between revisions
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The '''Tektronix Type 3A74''' is a four-channel vertical plug-in [[introduced in 1963]] for | 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. | [[560-series scopes]]. The bandwidth is DC to 2 MHz. | ||
A modified 3A74 (with a charge pre-amplifier on channel 1 to accommodate piezoelectric pressure transducers) was part of the [[Engine Analyzer]] package. | |||
{{BeginSpecs}} | {{BeginSpecs}} | ||
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==Internals== | ==Internals== | ||
Each input signal passes through | Each input signal passes through switchable input attenuators and then into a cathode-follower | ||
switchable input attenuators and then into a cathode-follower made from a [[7586]] | made from a [[7586]] Nuvistor triode. That drives a PNP differential amplifier. The output of this | ||
Nuvistor triode. That drives a PNP differential amplifier. The output of this | |||
differential amplifier, for each of the four channels, passes through a diode-based | 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, | analog signal switching network (multiplexer). The output of that multiplexer drives the output amplifier, | ||
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These can be a [[:Category:Repair_issues|maintenance issue]]. | These can be a [[:Category:Repair_issues|maintenance issue]]. | ||
==Links== | ==Links== | ||
* [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/3A74.htm Tek 3A74 | * [http://www.amplifier.cd/Test_Equipment/Tektronix/Tektronix_other/3A74.htm Tek 3A74 @ amplifier.cd] | ||
* http://www.barrytech.com/tektronix/vintage/tek3a74.html | * [http://www.barrytech.com/tektronix/vintage/tek3a74.html Tek 3A74@ barrytech.com] | ||
==Pictures== | ==Pictures== | ||
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File:3a74 amp schem.png|Amplifier | File:3a74 amp schem.png|Amplifier | ||
File:Tek 311-0304-00 pot.jpg|VAR GAIN potentiometer, sometimes problematic | File:Tek 311-0304-00 pot.jpg|VAR GAIN potentiometer, sometimes problematic | ||
</gallery> | </gallery> | ||
[[Category:560 series plugins]] | [[Category:560 series plugins]] | ||
Revision as of 03:14, 19 December 2015
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 (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 |
|
Internals
Each input signal passes through switchable input attenuators and then into a cathode-follower made from a 7586 Nuvistor triode. That drives 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-ohm potentiometers in for the VAR GAIN controls. These can be a maintenance issue.
Links
Pictures
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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
