7A12
The Tektronix 7A12 is a 120 MHz dual-trace vertical plug-in for 7000-series scopes. This original 7000-series plugin allows to compensate large dc offset voltages, however the offset voltage is not available on the front panel to be measured externally as with the 7A11.
Switches on the front panel control miniature relays in the signal path, such as those selecting input attenuators, through logic circuits. It uses the 155-0032-00 as a gain stage and the 155-0022-00 for channel switching.
The 7A12 was designed by Roy Hayes (who also designed the 3A3 and 3A8 before leaving for HP Loveland in Jan 1971). The Evaluation Engineer for the 7A12 was Peter Starič, co-author of the book "Wideband Amplifiers" with Erik Margan.
There were two mistakes, concept errors, that doomed the 7A12 from day 1. The first was in deciding to use the Tektronix IC process (the "Standard Process") for the signal path. This process had an Ft of only 1GHz, too slow for a plugin expected to provide 150MHz bandwidth in the fastest mainframe, the 7704.
The second day 1 mistake, later pointed out by Tom Rousseau, was to arrange the two channels vertically. Roy wanted to be able to go from one sensitivity (deflection factor) to another without having to go through all the sensitivities in between as happens with a rotary switch. The non-obvious problem with this is that the two channels, each on its own circuit board, would not be two identical boards. The boards would be mirror images! That is far more expensive.
Tom Rousseau was later tapped to design a new dual trace plugin that had adequate bandwidth and be less expensive to manufacture. Tom had the advantage of a later, faster IC process. He chose the M84 (155-0078-xx), already in production for the 485.
Key Specifications
| Bandwidth | 120 MHz (79xx) / 105 MHz (77xx) / 55 MHz (74xx) |
|---|---|
| Deflection | 5 mV/Div to 5 V/Div (1–2–5), variable up to 12.5 V/Div |
| Input impedance | 1 MΩ // 24 pF |
| Timing | Delay difference between channels < 500 ps |
| Channel isolation | At least 3000:1 at 75 MHz |
| Maximum input | 350 V DC + Peak AC at 1 kHz or less |
| DC offset | At least ±500 divisions |
Links
Documents Referencing 7A12
| Document | Class | Title | Authors | Year | Links |
|---|---|---|---|---|---|
| Tekscope 1969 V1 N5 Oct 1969.pdf | Article | Introducing the New Generation | 1969 | 7000-series scopes • 7504 • 7704 • 7A11 • 7A12 • 7A13 • 7A14 • 7A16 • 7A22 • 7S11 • 7M11 • 7B50 • 7B51 • 7B70 • 7B71 • 7T11 • R5030 • 7000 series readout system • Miniature relays • Cam switches • Industrial Design • T7500 • T7700 • P6052 • P6053 • C-50 • C-51 • 204-2 | |
| Tekscope 1969 V1 N6 Dec 1969.pdf | Article | A New Logic for Oscilloscope Displays | 1969 | 7000-series scopes • 7A11 • 7A12 • 7A13 • 7A14 • 7A16 • 7A22 • 7B50 • 7B51 • 7B70 • 7B71 • 7S11 • 7T11 • 7504 • 7704 | |
| 7000 series brochure March 1973.pdf | Brochure | 7000 series brochure, March 1973 | 1973 | 7A11 • 7A12 • 7A13 • 7A14 • 7A15A • 7A16A • 7A17 • 7A18 • 7A19 • 7A21N • 7A22 • 7B50 • 7B53A • 7B70 • 7B71 • 7B92 • 7CT1N • 7D11 • 7D13 • 7D14 • 7D15 • 7M11 • 7L12 • 7S11 • 7S12 • 7T11 • 7704A • R7704 • 7904 • R7903 • 7603 • R7603 • 7403N • R7403N • 7313 • R7313 • 7613 • R7613 • 7623 • R7623 • P7001 |
Pictures
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Front view
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Front view
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Attenuator schematic with relays
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7A12 Amplifier PCB
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Left side view
Components
Some Parts Used in the 7A12
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 148-0034-01 | 148-0034-01 | Discrete component | miniature DPDT relay | 485 • 7A12 |
| 148-0034-02 | 148-0034-02 | Discrete component | miniature DPDT relay | 7A12 |
| 155-0022-00 | 155-0022-00 • 155-0022-01 | Monolithic integrated circuit | analog multiplexer | 147 • 148 • 149 • 335 • 468 • 1430 • 1441 • 1461 • 1900 • 1910 • 2220 • 2221 • 2230 • 5223 • 5403 • 5440 • 5441 • 5443 • 5444 • 5A38 • 7313 • 7403N • 7503 • 7504 • 7514 • 7603 • AN/USM-281C • 7613 • 7623 • 7623A • 7633 • 7704 • R7704 • 7704A • 7834 • 7844 • 7854 • R7912 • 7912AD • 7912HB • 7904 • R7903 • 7904A • 7934 • 7A12 • 7A18 • 7A18A • 7A18N • 7B52 • 7B53N • 7D10 • 7D11 • 7D12 • NT-7000 • P7001 |
| 155-0032-00 | 155-0032-00 • 155-0032-01 | Monolithic integrated circuit | variable-gain transconductance amplifier (voltage in, current out) | 335 • 464 • 465 • 465B • 466 • 475 • 475A • 475M • 634 • 650 • 651 • 652 • 653 • 655 • 656 • 670 • 671 • 7A12 • 475 • FG504 • 1440 • 1460 • 1480 • 1481 • 1482 • 1485 |