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7A12: Difference between revisions
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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]]. | 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 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. | ||
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 | The solution was two separate, mirror image attenuators and two identical amplifier boards all attached to a main vertically-centered circuit board. The two identical amplifier circuit boards, one mounted on each side of a center board, are cleverly flipped so both face outward from the center board. This is accomplished by having one near the top rail and the other near the bottom rail. There are two pairs of output sockets, only one of which is used per channel. 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 with circuitry similar to the 7A18. This was the 200 MHz [[7A26]]. It became the best selling Tektronix plugin of all time. Tektronix literally gold plated a 7A26 and gave it to Tom in recognition. | |||
See https://vintagetek.org/100000-7a26-plug-in/ | See https://vintagetek.org/100000-7a26-plug-in/ | ||