7A42
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, available to the horizontal plug-ins when the 7A42 is installed in the two vertical bays.
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 |
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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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| Trigger Hysteresis | 40/400 mV (TTL), 8/80 mV (ECL) |
| Features |
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| 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 |
| 7D20 SMPS AnalysisDFT Apr1984.pdf | Article | Use a personal computer and DFT to extract data from noisy signals | Clark Foley • Jim Lamb | 1984 | 7854 • 7A42 • 7D20 |
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 • 326 • 7A11 • 7A12 • 7A13 • 7A14 • 7A16 • 7A16P • 7A22 • 7A42 • 7B42N • 7B50 • 7B51 • 7B52 • 7B53A • 7B70 • 7B71 • 7B92 • 7B92A • 7D10 • 7D11 • 7D12 • 7D14 • 7D15 • 7D20 • 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 |
|---|---|---|---|---|
| 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 |
| 2764 | Monolithic integrated circuit | 8K×8 EPROM | 5D10 • 7A42 • AA5001 • DA4084 • Keithley 175 • Keithley 580 | |
| 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 • 5D10 • 7A42 • 7D02 • AFG5101 • AFG5102 • PFG5105 |
| Intel 8279 | 156-1535-00 | Monolithic integrated circuit | keyboard controller | 1781R • 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 • 4041 • 7A42 • DP100 • SPG-271 • TDS540 • TDS544A • TDS620 • TDS640 • TDS640A • TDS644A |