7A42

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	7A42 • 7D11 • 7D15

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	Back-lit switches • 7A11 • 7A12 • 7A13 • 7A14 • 7A16 • 7A16P • 7A22 • 7A42 • 7B42N • 7B50 • 7B51 • 7B52 • 7B53A • 7B70 • 7B71 • 7B92 • 7B92A • 7D10 • 7D11 • 7D12 • 7D114 • 7D15 • 7D20 • 7F10 • 7L5 • 7L12 • 7L13 • 7L14 • 7L18 • 7M13 • 7S11 • 7S12 • 7T11 • 067-0587-00 • 067-0587-01 • 067-0587-02 • 067-0587-10
Patent US 4513417A	Automatic processor restart circuit	James S. Lamb • Warren K. Wimmer	1982-11-29	1985-04-23	7A42
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	7A42

See also

• 067-1155-99
• A6701
• 821

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

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  display - four signal traces plus trigger view

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  7A42 rear view

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  7A42 top view

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  Schematic cartoon: Bus

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  Schematic cartoon: Chirp

Internal

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  amplifier board (one attenuator cover removed)

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  amplifier board front - attenuators, amplifiers, channel switches

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

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  attenuator, cover removed

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  attenuator cover

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  attenuator, top

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  attenuator, one relay actuator removed

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  attenuator, all relay actuators removed

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  attenuator, all relay actuators removed

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  microprocessor board

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  memory backup battery on microprocessor board replaced with LiIon

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  internal switch mode PSU for digital logic supplies

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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
Intel 8085A	156-1088-00	Monolithic integrated circuit	8-bit microprocessor	308 • 468 • 4025 • 7A42 • 7D02 • AFG5101 • AFG5102
Intel 8279	156-1535-00	Monolithic integrated circuit	keyboard controller	7A42 • AFG5101
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