7A12: Difference between revisions

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Tektronix 7A12
120 MHz dual-channel amplifier 7A12 front view Compatible with 7000-series scopes Produced from 1969 to 1974 Manuals Tektronix 7A12 Manual (OCR) Alternate Tektronix 7A12 Manual @ BAMA (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

The Tektronix 7A12 is a 120 MHz dual-trace vertical plug-in for 7000-series scopes. This original 7000-series plugin allows 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 to select 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 one. The first was in deciding to use the 1 GHz Tektronix IC process (called 50/450 for resistivities of the two base layers) for the signal path. This process was too slow for a plugin expected to provide 150MHz bandwidth in the fastest mainframe, the 7704.

The second day one mistake, later pointed out by Tom Rousseau, was to arrange the two channels side by side. 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 vertical row of push buttons was functionally attractive. The complexity required three circuit boards, two small identical circuit boards, one on each side of a center board (both facing the same direction). That is expensive and complex.

Tom Rousseau designed a new dual trace plugin with discrete components on a single circuit board that had 80 MHz bandwidth and was much less expensive to manufacture. He did this on his own, not at management's request. Management liked it and it became the 7A18. Later Tom had the advantage of a 3 GHz IC process (SHF2). He used the M84 (155-0078-xx), already in production for the 485, and circuitry similar to the 7A18. This was the 200 MHz 7A26. It became the best selling Tektronix plugin of all time. Tektronix made a literally gold-plated 7A26 and gave it to him in recognition.

See https://vintagetek.org/100000-7a26-plug-in/

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	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

Front view
Front view
Attenuator schematic with relays
7A12 Amplifier PCB
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

@@ Line 28: / Line 28: @@
 The second day one mistake, later pointed out by Tom Rousseau, was to arrange the two channels side by side.  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 vertical row of push buttons was functionally attractive.  The complexity required three circuit boards, two small identical circuit boards, one on each side of a center board (both facing the same direction). That is expensive and complex.
-Tom Rousseau designed a new dual trace plugin with discrete components on a single circuit board that had 80 MHz bandwidth and was much less expensive to manufacture. He did this on his own, not at management's request.  Management liked it. It became the 7A18.  Later Tom had the advantage of a 3 GHz IC process (SHF2).  He used the M84 (155-0078-xx), already in production for the 485, and circuitry similar to the 7A18.  This was the 200 MHz 7A26.  It became the best selling Tektronix plugin of all time.  Tektronix made a literally gold-plated 7A26 and gave it to him in recognition.
+Tom Rousseau designed a new dual trace plugin with discrete components on a single circuit board that had 80 MHz bandwidth and was much less expensive to manufacture. He did this on his own, not at management's request.  Management liked it and it became the 7A18.  Later Tom had the advantage of a 3 GHz IC process (SHF2).  He used the M84 (155-0078-xx), already in production for the 485, and circuitry similar to the 7A18.  This was the 200 MHz 7A26.  It became the best selling Tektronix plugin of all time.  Tektronix made a literally gold-plated 7A26 and gave it to him in recognition.
 See https://vintagetek.org/100000-7a26-plug-in/