7A42

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.

Manuals – Specifications – Links – Pictures

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. The trigger level is set digitally and shown on a 7-segment display.

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.

Key Specifications

Bandwidth	350 MHz
Deflection	0.1 / 0.2 / 0.5 V/Div (TTL mode) 20 / 50 / 100 mV/Div (ECL mode) each direct or through 10:1 probe
Input impedance	1 MΩ // 15 pF or 50 Ω
Max. input voltage	at 1 MΩ: 25 V (DC+peak AC) below 36 MHz, down to 3 VAC at 300 MHz at 50 Ω: 5 VRMS during any 1 ms interval
Trigger level	−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)
Hysteresis	40 mV (TTL), 8 mV (ECL) (or ×10)
Features	NiCd battery to preserve front-panel control status
Weight	2.8 kg / 6.2 lb

Internals

The 7A42's functions are controlled by an Intel 8085A 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 119-1517-00 input attenuator modules contains five 148-0145-00 miniature bi-stable relay actuators. These have four long pins plugging in to the base board and contact springs directly shorting pads on the thick-film ceramic substrate. The relay coils are wired in a 4×5 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.

There is a NiCd backup battery that allows the unit to retain its last configuration.

A 555 timer implements a 15 ms "real-time clock" and watchdog reset, another drives a beeper.

See also

• 067-1155-99
• A6701
• 821

Pictures

• 
• 
• 
• 
• 
• 
• 
• 

  display - four signal traces plus trigger view

• 
• 

  7A42 rear view

• 

  7A42 top view

• 

  Schematic cartoon: Bus

• 

  Schematic cartoon: Chirp

Internal

• 

  amplifier board (one attenuator cover removed)

• 

  amplifier board front - attenuators, amplifiers, channel switches

• 

  amplifier board rear - channel switches, two 15 ns delay lines

• 

  attenuator, cover removed

• 

  attenuator, top

• 

  attenuator, one relay actuator removed

• 

  attenuator, all relay actuators removed

• 

  attenuator, all relay actuators removed

• 

  microprocessor board

• 

  memory backup battery on microprocessor board replaced with LiIon

• 

  internal switch mode PSU for digital logic supplies

• 
• 
• 

Components

Some Parts Used in the 7A42

Part	Part Number(s)	Class	Description	Used in
148-0145-00	148-0145-00	Discrete component	miniature bi-stable relay actuator	7A42 • 119-1517-00
155-0038-01	155-0038-00 • 155-0038-01	Monolithic integrated circuit	5-bit current source D/A converter	7A42 • 7D13 • 7D14 • 7M13 • T4005
155-0078-00	155-0078-xx • 155-0273-00 • 155-0274-00	Monolithic integrated circuit	broadband amplifier	464 • 465 • 466 • 468 • 475 • 475A • 475M • 485 • 7834 • 7844 • 7854 • 7904 • R7903 • R7912 • 7912AD • 7912HB • 7104 • 7A16A • 7A16P • 7A24 • 7A26 • 7A42 • 067-0587-01 • 067-0680-00 • AM503 • PG502 • PG508 • DC510 • DC5010 • FG5010
155-0236-00	155-0236-00	Hybrid integrated circuit	channel switch	2445 • 2465 • 2467 • 7A42
ICM7218	156-1621-00 • 156-1622-00	Monolithic integrated circuit	8-digit, 7-segment LED driver	7A42 • SG5010
Intel 8085A	156-1088-00	Monolithic integrated circuit	8-bit microprocessor	308 • 468 • 4025 • 7A42 • 7D02 • AFG5101 • AFG5102 • PFG5105
Intel 8279	156-1535-00	Monolithic integrated circuit	keyboard controller	7A42 • AFG5101 • DM5010 • FG5010 • PFG5105
SG3524	156-0933-00 • 156-0933-01 • 156-1585-00 • 156-1585-01	Monolithic integrated circuit	PWM switch-mode controller	067-1011-00 • 1502B • 1502C • 1503B • 1503C • 7A42 • DP100