7A42

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Tektronix 7A42
350 MHz four-channel logic triggered amplifier
7A42 front view

Compatible with 7000-series scopes

Produced from 1984 to 1990

Manuals
ROM Images
File Pos. Checksum
160-1959-00 A8U145 2e9a8923
160-1960-00 A8U245 c31d60f0
160-1961-00 A8U340 1e8c4ba6
(All manuals in PDF format unless noted otherwise)
Manuals – Specifications – Links – Pictures

The Tektronix 7A42 is a four-channel 350 MHz plug-in for 7000-series scopes. It is a double-wide plug-in, designed by Kirk Wimmer.

Vertical:

The 7A42 was specifically designed for logic signals (TTL, ECL, CMOS). It is not a Logic Analyzer however – the signal path and display is analog.
The input V/div setting can only be seen in the mainframe's readout, and adapts automatically when a pin-coded ×10 probe is attached. (×100 probes are not supported and are incorrectly recognized as ×10.)
A fifth trace, "Trigger View", displays the trigger function output or external clock input.

Triggering:

The 7A42 supports triggering based on Boolean conditions of the four inputs.
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 when active.
There are two sets of trigger 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 "A then B" interval gate signal can be routed to a counter for time measurement or event counting.
Selected by an internal jumper, the front-panel trigger output can be configured for either the trigger signal, or the "A then B" interval
The trigger level is set digitally for each channel, and shown on a 7-segment display. The trigger level display can also be used as a DVM to measure the offset voltage to which which an attached P6230 probe is set.

Mainframe Interface:

Signal/Trigger outputs and mainframe readout use the left slot, allowing the 7A42 to be installed in the two center bays in a four-bay mainframe, together with another vertical plug-in in the left vertical bay.
The right slot additionally provides the "A then B" interval gate on the trigger lines.
There is a jumper to allow the readout to work in a 7854 mainframe.

Probes:

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.

Key Specifications

Bandwidth 350 MHz in 7104, 300 MHz in 7904
Deflection
  • TTL mode: 0.1, 0.2 or 0.5 V/div ; 1, 2 or 5 V/div with ×10 probe
  • ECL mode: 20, 50 or 100 mV/div ; 0.2, 0.5 or 1 V/div with ×10 probe
  • always DC coupled
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
  • TTL Mode ×1: −1.27 to +1.28 V in 10 mV steps (Preset: 0.14 V)
  • TTL Mode ×10: −12.7 to +12.8 V in 100 mV steps (Preset: 1.4 V)
  • ECL Mode ×1: −0.254 V to +0.256 V in 2 mV steps (Preset: –0.13 V)
  • ECL Mode ×10: −2.54 V to +2.56 V in 2 mV steps (Preset: –1.3 V)
Trigger Hysteresis 40/400 mV (TTL), 8/80 mV (ECL)
Features
  • NiCd battery to preserve front-panel control status
Weight 2.8 kg / 6.2 lb

Links

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

Documents Referencing 7A42

Document Class Title Authors Year Links
42W-5588.pdf Application Note Advanced Triggering Techniques Roger Ensrud 1984

Patents that may apply to 7A42

Page Title Inventors Filing date Grant date Links
Patent US 3584174A Push-button switch apparatus having cam actuated switch contacts and selective illumination means Tony Sprando Peter S Winkelmann 1969-06-09 1971-06-08
Patent US 4513417A Automatic processor restart circuit James S. Lamb Warren K. Wimmer 1982-11-29 1985-04-23
Patent US 4585975A High speed Boolean logic trigger oscilloscope vertical amplifier with edge sensitivity and nested trigger Warren K. Wimmer 1983-04-21 1986-04-29

See also

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, driving two solenoids that move a yoke which is held in the last active position by a permanent magnet. The yoke moves a pair of contact springs that directly short corresponding 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.

An internal jumper enables partial compatibility with a 7854 mainframe in storage mode (displaying any single channel, 1+2 in ALT, or 3+4 in ALT only). There are no restrictions with the 7854 in analog mode.

Pictures

Internal

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