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→Challenges in the Horizontal Signal Path
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===Challenges in the Horizontal Signal Path=== | ===Challenges in the Horizontal Signal Path=== | ||
Many vertical plug-ins employed an “ALT” mode, where the input channels are switched (A to B, Ch1 to Ch2) | Many vertical plug-ins employed an “ALT” mode, where the input channels are switched (A to B, Ch1 to Ch2) | ||
after the end of a sweep at a time when the beam is turned off hiding the visibility of the transition. | after the end of a sweep at a time when the beam is turned off hiding the visibility of the transition. | ||
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until the B sweep had entered the holdoff state or was waiting. | until the B sweep had entered the holdoff state or was waiting. | ||
Since the 500-series plug-in ‘scopes had a 67.5 V plug-in/mainframe common-mode DC level, | Since the 500-series plug-in ‘scopes had a | ||
[[500_Series_plug-in_interface|67.5 V plug-in/mainframe common-mode DC level]], | |||
the possibilities of destruction of expensive solid-state devices due to a misplaced probe were rampant, | the possibilities of destruction of expensive solid-state devices due to a misplaced probe were rampant, | ||
often resulting in a string of expletives. Attempting to moderate the situation, | often resulting in a string of expletives. Attempting to moderate the situation, | ||
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I went over to see what had happened, and I saw the fellow shaking his finger at the part of the circuit where my errant short had occurred. | I went over to see what had happened, and I saw the fellow shaking his finger at the part of the circuit where my errant short had occurred. | ||
He was getting redder by the second, prompting me to say, “you gotta let it out!”. He walked over to the cuss box and loudly said. “Damn!”, put a nickel in. | He was getting redder by the second, prompting me to say, “you gotta let it out!”. He walked over to the cuss box and loudly said. “Damn!”, put a nickel in. | ||
Then he thought about it and said “Damn!” again, dropping another one in. He looked at me and said, “I feel much better now”. | Then he thought about it and said “Damn!” again, dropping another one in. | ||
He looked at me and said, “I feel much better now”. | |||
Nearing Christmas of 1965, our operating rule was 12 hours a day, | Nearing Christmas of 1965, our operating rule was 12 hours a day, | ||
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I found that the negative-going output cathode follower was late in following the ramp, | I found that the negative-going output cathode follower was late in following the ramp, | ||
causing the electron beam’s axial velocity to increase due to the increased common-mode voltage, | causing the electron beam’s axial velocity to increase due to the increased common-mode voltage, | ||
reducing the deflection sensitivity. The design, first appearing in the Tek 531, employs a pentode whose grid, | reducing the deflection sensitivity. | ||
driven by the differentiated positive-going ramp, boosts the pull-down current, keeping the cathode follower in conduction. | The design, first appearing in the [[531|Tek 531]], employs a pentode whose grid, | ||
Our circuit had been inherited from the 544-546-547 ‘scopes, and when I questioned the designer about the effect, | driven by the differentiated positive-going ramp, boosts the pull-down current, | ||
keeping the cathode follower in conduction. | |||
Our circuit had been inherited from the 544-546-547 ‘scopes, | |||
and when I questioned the designer about the effect, | |||
he said, “I always wondered … “. Some fiddling with currents and time constants diminished the effect. | he said, “I always wondered … “. Some fiddling with currents and time constants diminished the effect. | ||