From TekWiki
Jump to navigation Jump to search
Tektronix 7A21N
Direct Access plug-in
7A21 front panel

Compatible with 7000-series scopes

Produced from 1972 to 1979

(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix 7A21N is a 7000-series plug-in that provides direct access to the CRT for fast-risetime - AC signals on the 500 MHz-class 7900 series scopes, i.e. 7904/7904A, R7903, 7934, R7912.

Input signals are applied via a pair of GR-874 connectors.

The 7A21N is fully passive and can be wired for single-ended or differential signals internally. It includes two delay lines, two inverting "transformers" and a passive bridge and power divider. There is no trigger pick-off, this would have to be provided externally e.g. through a 7M11.

The 7A21N is intended to be installed in the Left Vertical bay of the 79xx mainframe and requires the mainframe's vertical amplifier board to be replaced with the 7A21N CRT Input Network and 7A21N CRT Termination boards, which are shipped plugged into the back side of the 7A21N circuit board. (A second-hand 7A21 without these boards and associated cables is useless!)

Obviously, installing the replacement boards also disables the mainframe's readout facility and second vertical plug-in bay.

Key Specifications

Deflection < 4 V/Div (SE), < 2 V/Div (Differential)
Bandwidth 20 kHz – 1 GHz
Input impedance 50 Ω
Max. input 6 W avg @ 50 Ω, 200 V DC



Precursor/prototype to the 7A21N: