7A12: Difference between revisions

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7A12 (view source)

Revision as of 11:33, 8 September 2024

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Switches on the front panel control [[miniature relays]] in the signal path to select input attenuators, through logic circuits.
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 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.
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.  However, that would require both channels to occupy the same space on a single vertical circuit board. The solution was three circuit boards, two small identical circuit boards, one on each side of a center board. Both small identical boards face the same direction so they don't have to be separate mirror image boards). 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/


{{BeginSpecs}}
{{BeginSpecs}}
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{{Spec | DC offset        | At least ±500 divisions}}
{{Spec | DC offset        | At least ±500 divisions}}
{{EndSpecs}}
{{EndSpecs}}
==Internals==
The 7A12 uses the [[155-0032-00]] as a gain stage and the [[155-0022-00]] for channel switching.
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 150 MHz 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.  However, that would require both channels to occupy the same space on a single vertical circuit board. The solution was three circuit boards, two small identical circuit boards, one on each side of a center board. Both small identical boards face the same direction so they don't have to be separate mirror image boards). 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 Tom in recognition.
See https://vintagetek.org/100000-7a26-plug-in/


==Links==
==Links==
Retrieved from "https://w140.com/tekwiki/wiki/Special:MobileDiff/97135"

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