3A2

Manuals – Specifications – Links – Pictures

The Tektronix Type 3A2 is a dual-trace amplifier plug-in introduced in 1963 for 560-series scopes. It was designed for compatibility with the digital unit in the 567, e.g, the 6R1 or 6R1A.

Key Specifications

Bandwidth	500 kHz
Input impedance	1 MΩ // 47 pF
Deflection	10 mV/div to 25 V/div

Internals

The input signal passes through compensated attenuators and then into a 12AT7 cathode-follower stage. Channel switching in ALTERNATE mode is done using diodes. The output stage that drives the vertical deflection plates of the scope uses a pair of 6BA8 pentodes.

The "CHOP" mode of the 3A2 switches back and forth between the two inputs at a rate of a few kilohertz. The signal that causes the switching is generated by a relaxation oscillator formed using a capacitor and a pair of 152-108 Shockley diodes, D385 and D386.

Pictures

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  Channel 1 Input Amp

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  Channel 2 Input Amp

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  Switching and Output Amp

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  Attenuator Switches