7A42
The Tektronix 7A42 is a four-channel 350 MHz plug-in for 7000-series scopes. It was designed by Kirk Wimmer. It is a double-wide plug-in, with signal outputs and mainframe readout only using the left slot, allowing the it to be installed to the right of another plug-in in a four-bay mainframe.
The 7A42 was specifically designed for logic signals (TTL, ECL, CMOS) and supports triggering based on Boolean conditions of the four inputs. The signal path and display is analog, however. 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 to 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 |
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Deflection |
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Input impedance | 1 MΩ // 15 pF or 50 Ω |
Max. input voltage |
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Trigger level |
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Hysteresis | 40 mV (TTL), 8 mV (ECL) (or ×10) |
Features |
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Weight | 2.8 kg / 6.2 lb |
Links
Documents Referencing 7A42
Document | Class | Title | Authors | Year | Links |
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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 |
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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
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 |
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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 |