7A42: Difference between revisions

'''ROM images'''

The '''Tektronix 7A42''' is a four-channel 350 MHz plug-in for [[7000-series scopes]].  It is a double-wide plug-in, with signal outputs and mainframe readout only using the left slot.

It was specifically designed for logic signals (TTL, ECL, CMOS) and supports triggering based on Boolean conditions of the four inputs.

A fifth trace, "Trigger View", displays the trigger function output or external clock input.  

There are two sets of conditions, A and B, that can be individually selected or paired in an "A then B" mode called ''nested triggering'', where the occurrence of condition A arms the trigger and condition B causes the trigger to be generated.

The trigger can be qualified by an external clock.  A trigger filter control, variable from 0-300 ns, allows events shorter than the selected length to be suppressed.  A TTL-level "reset" input will inhibit the trigger if active.

Selected by an internal jumper, either the trigger signal, or the "A then B" interval, is available on a front-panel trigger output. This can e.g. be routed a counter for time measurement or event counting.  

The input V/Div setting can only be seen in the mainframe's readout.  There is a jumper to allow the readout to work in a [[7854]] mainframe.

Tektronix recommended the [[P6131]], 300 MHz, 10 MΩ ×10 probe, and the [[P6230]], 1.5 GHz, 450/50 Ω ×10, variable-offset probe for ECL circuits.

The [[067-1155-99]] calibration fixture is specific to the 7A42.

{{Spec | Bandwidth | 350 MHz}}

* 0.1 / 0.2 / 0.5 V/Div (TTL mode)

* 20 / 50 / 100 mV/Div (ECL mode)

* each direct or through 10:1 probe}}

{{Spec | Input impedance | 1 MΩ // 15 pF or 50 Ω}}

* −1.27 to +1.28 V (TTL mode) in 10 mV steps

* −254 mV to +256 mV (ECL mode) in 2 mV steps (or ×10)}}

{{Spec | Hysteresis | 40 mV (TTL), 8 mV (ECL) (or ×10)}}

The 7A42's functions are controlled by an [[Intel 8085]]A microprocessor, with code in three 2764 EPROMs (a fourth ROM socket is unused).  The front-panel pushbuttons are handled by an Intel 8279 keyboard controller.

Each of the four input attenuator circuits contains five [[miniature relays]]. The bistable relay coils are wired in a 4x5 matrix.

The 7A42 contains its own switch mode PSU, based on an SG3524 controller, that generates +5 V, −2 V and −5 V from the mainframe's ±50 V rails.

* [[067-1155-99]]

* [[821]]

Tek 7a42 fr8.jpg | memory backup battery

Tek 7a42 fr10.jpg | microprocessor board  

Tek 7a42 fr11.jpg | amplifier board front - attenuators, amplifiers, channel switches  

Tek 7a42 fr12.jpg | amplifier board rear - channel switches, two 15 ns delay lines