3A74: Difference between revisions

Revision as of 07:45, 13 August 2021

Tektronix 3A74
2 MHz four channel vertical amp 3A74 front Compatible with 560-series scopes Produced from 1962 to 1974 Manuals Tektronix 3A74 Manual (DjVu) Tektronix 3A74 Factory Calibration Procedure, July 1969‎ Tektronix 3A74 Calibration Outline (PDF, OCR) (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

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

US-made Version

Front Side
Rear Side
Left Side
Right Side
Block Diagram
Channel Switching
Amplifier
VAR GAIN potentiometer, sometimes problematic
3A74 Engine Analyzer Amplifier

Netherlands-made Version

@@ Line 1: / Line 1: @@
-{{Plugin Sidebar 2|
-title=Tektronix 3A74|
+{{Plugin Sidebar
-summary=2 MHz four channel vertical amp|
+|manufacturer=Tektronix
-image=Tek_3A74_front_crop.jpg |
+|series=560-series scopes
-caption=3A74 front|
+|type=3A74
-introduced=1962 |
+|summary=2 MHz four channel vertical amp
-discontinued=1974 |
+|image=Tek_3A74_front_crop.jpg
-series=[[560-series scopes]]|
+|caption=3A74 front
-manuals=
+|introduced=1962
+|discontinued=1974
+|manuals=
 * [http://bama.edebris.com/download/tek/3a74/3a74.djvu Tektronix 3A74 Manual (DjVu)]
 * [[Media:Tek 3a74 fcp july 1969.pdf|Tektronix 3A74 Factory Calibration Procedure, July 1969‎]]
 * [[Media:Tek 3a74 cal outline.pdf|Tektronix 3A74 Calibration Outline (PDF, OCR)]]
 }}
-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 MOD 730A (with a charge pre-amplifier on channel 1 to accommodate piezoelectric pressure transducers)
+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.
-was part of the [[Engine Analyzer]] package.
 {{BeginSpecs}}