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556: Difference between revisions
→Challenges in the Vertical Signal Path
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[[File:Two 8608 tubes.jpg|thumb|A pair of 8608 tubes.]] | [[File:Two 8608 tubes.jpg|thumb|A pair of 8608 tubes.]] | ||
[[File:Tek 556 vert amp output.jpg|thumb|Vertical output tubes. The beige rectangular components are 1kΩ plate resistors. In addition to reducing parasitics, moving the anode connection to the top on the 8608 tube allows the plate resistors, which dissipate a few watts, to be in the air stream from the fan.]] | [[File:Tek 556 vert amp output.jpg|thumb|Vertical output tubes. The beige rectangular components are 1kΩ plate resistors. In addition to reducing parasitics, moving the anode connection to the top on the 8608 tube allows the plate resistors, which dissipate a few watts, to be in the air stream from the fan.]] | ||
Oliver’s requirement to emulate the 547's sweep switching feature in the dual-beam 556 meant that | Oliver’s requirement to emulate the 547's sweep switching feature in the dual-beam 556 meant that | ||
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already elevated due to the vacuum tube output stage, from increasing further. | already elevated due to the vacuum tube output stage, from increasing further. | ||
At that time, no silicon transistors were available that could meet the speed and voltage requirements, | At that time, no silicon transistors were available that could meet the speed and voltage requirements, | ||
so we were constrained to use the 2N2929, a PNP germanium transistor that could barely meet the voltage and power dissipation requirements. | so we were constrained to use the [[2N2929]], | ||
a PNP germanium transistor that could barely meet the voltage and power dissipation requirements. | |||
<ref> | <ref> | ||
In the mid-60s, Tektronix had no resident IC design or fabrication facility, | In the mid-60s, Tektronix had no resident IC design or fabrication facility, | ||
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together with the need for high writing speed and small spot size always limited the performance of vertical amplifiers. | together with the need for high writing speed and small spot size always limited the performance of vertical amplifiers. | ||
</ref> | </ref> | ||
The seven or eight inches of 93 ohm coaxial cable required a couple of additional time constants to compensate for skin-effect loss. | The seven or eight inches of 93 ohm coaxial cable required | ||
a couple of additional time constants to compensate for skin-effect loss. | |||
Another germanium limitation was in the power supply's series pass transistors, | Another germanium limitation was in the power supply's series pass transistors, | ||
where the Delco DTG2400 PNP transistor was the only suitable part available. | where the Delco DTG2400 PNP transistor was the only suitable part available. | ||
After a break at serial number 2000, a major mod replaced the germanium parts with a design incorporating newly available silicon devices. | After a break at serial number 2000, | ||
a major mod replaced the germanium parts with a design incorporating newly available silicon devices. | |||
An aside – in the design of bleeding-edge electronic equipment, there can be a few bright ideas, | An aside – in the design of bleeding-edge electronic equipment, there can be a few bright ideas, | ||
followed by “yeahbuts”, as in, “yeah, but you’re gonna have to … “. Some projects end up staggering under the sheer load of the “yeahbuts”. | followed by “yeahbuts”, as in, “yeah, but you’re gonna have to … “. Some projects end up staggering under the sheer load of the “yeahbuts”. | ||
The recent Boeing 737Max debacle comes to mind with its problems associated with engine placement, ground clearance, and thrust centroids, | The recent Boeing 737Max debacle comes to mind with its problems associated with engine placement, ground clearance, and thrust centroids, | ||
oh, and various kinds of cost issues. It’s one of those things that cause most designers to revere the Dilbert comic strip. | oh, and various kinds of cost issues. | ||
It’s one of those things that cause most designers to revere the Dilbert comic strip. | |||
===Challenges in the Horizontal Signal Path=== | ===Challenges in the Horizontal Signal Path=== | ||