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556: Difference between revisions
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{{Oscilloscope Sidebar | | {{Oscilloscope Sidebar | ||
|manufacturer=Tektronix | |||
summary=50 MHz dual beam scope| | |series=500-series scopes | ||
image=556-crop.jpg| | |model= 556 | ||
caption=Tektronix 556 front| | |summary=50 MHz dual beam scope | ||
introduced=1966 | | |image=556-crop.jpg | ||
discontinued=1975 | | |caption=Tektronix 556 front | ||
manuals= | |introduced=1966 | ||
|discontinued=1975 | |||
* [[Media:070-0757-00.pdf|Tektronix 556 Manual | |designers=Phil Crosby;Larry Biggs;Ron Olson;Arend Kastelein | ||
|manuals= | |||
* [[Media:070-0757-00.pdf|Tektronix 556 Manual]] (OCR) | |||
<small> | <small> | ||
'''Lecture Notes''' | |||
* [[Media:556 Lecture Notes.pdf|Tektronix 556 Lecture Notes]] | |||
* [[Media:tek_556_lecture_notes.pdf|Tektronix 556 Lecture Notes]] (bad-OCR) | |||
'''Calibration''' | |||
* [[Media:Tek 556 fcp.pdf|Tektronix 556 Factory Calibration Procedure, Jan 1968, SN 2000-up]] | |||
* [[Media:Tek 556 fcp feb 1967.pdf|Tektronix 556 Factory Calibration Procedure, Feb 1967]] | |||
* [[Media:Tek 556 cal outline.pdf|Tektronix 556 Calibration Outline]] | |||
'''Modifications''' | '''Modifications''' | ||
* [[Media:050-0479-01.pdf|Disconnect Diode 556 Serials 100-2989 w/exceptions & R556 100-1989 w/exceptions | * [[Media:050-0479-01.pdf|Disconnect Diode 556 Serials 100-2989 w/exceptions & R556 100-1989 w/exceptions]] | ||
</small> | </small> | ||
}} | }} | ||
The '''Tektronix 556''' is a 50 MHz [[dual-beam scopes|dual-beam scope]], the successor to the Tektronix [[555]]. It uses [[letter-series and 1-series plug-ins]]. A rack-mount version, the R556, also exists. | |||
The '''Tektronix 556''' is a 50 MHz [[dual-beam scopes|dual-beam scope]], the successor to the Tektronix [[555]]. | |||
It uses [[letter-series and 1-series plug-ins]]. | |||
A rack-mount version, the R556, also exists. | |||
The 556, which is wider than the average 500-series scope, fits in the [[205]] cart. | The 556, which is wider than the average 500-series scope, fits in the [[205]] cart. | ||
The 556 was the last 500-series scope produced. | The 556 was the last 500-series scope produced. It was present in the [[Media:1974_Tektronix_Catalog.pdf|1974 catalog]], but gone in the [[Media:1975_Tektronix_Catalog.pdf|1975 catalog]]. | ||
It was present in the [ | |||
but gone in the [ | |||
(The dual-beam [[7844]] had been introduced in 1974.) | (The dual-beam [[7844]] had been introduced in 1974.) | ||
{{ | {{BeginSpecs}} | ||
{{Spec|Bandwidth|≥50 MHz with 1-series plug-ins having a rise time of ≤3.12 ns}} | |||
{{Spec|Rise time|≤6.25 ns (tested with [[067-0521-00]]) }} | |||
{{Spec|Sweep|100 ns/div to 5 s/div, variable ≥2.5:1 (slowest sweep 12.5 s/cm); ×10 magnifier }} | |||
{{Spec|Trigger sensitivity| | |||
* AC: 0.2 div (int) / 200 mV (ext) from 10 Hz to 10 MHz; 1 div / 0.4 V to 50 MHz; LF REJ cut-off 2.5 kHz; HF REJ cut-off 60 kHz | |||
* DC: 0.35 div (int) / 200 mV (ext) from DC to 10 MHz; 2 div or 0.4 V to 50 MHz | |||
}} | |||
{{Spec|Ext. X|0.1 V/div or 1 V/div depending on magnifier setting, DC to ≥400 kHz; max. 50 V}} | |||
{{Spec|Ext. Z|10 V<sub>p-p</sub> for "noticeable modulation intensity", 1 MΩ input}} | |||
{{Spec|Power|90-110/104-126/112-136/180-220/208-252/224-272 V<sub>RMS</sub>, 50 to 60 Hz (400 Hz with fan modification); 840 W/1 kVA max.}} | |||
{{Spec|CRT| [[T5560]]-31-1 ([[154-0500-00]]), P31 standard, 10 kV acceleration; 10 cm × 8 cm }} | |||
{{EndSpecs}} | |||
==Links== | ==Links== | ||
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Each of the transformers is driven by its own independent oscillator using a [[6GF5]] power pentode. | Each of the transformers is driven by its own independent oscillator using a [[6GF5]] power pentode. | ||
==The 556 Story, as recalled by engineer [[Phil Crosby]]== | ==The 556 Story, as recalled by engineer [[Phil Crosby]] in September 2020== | ||
[[File:Phil and 556.jpg|thumb|Phil Crosby then and now, with a Tektronix Type 556 and spare CRT at the VintageTEK Museum in Beaverton, Oregon.]] | [[File:Phil and 556.jpg|thumb|Phil Crosby then and now, with a Tektronix Type 556 and spare CRT at the VintageTEK Museum in Beaverton, Oregon.]] | ||
<!--Phil Crosby then and now, with a Tektronix Type 556 and spare CRT at the VintageTEK Museum in Beaverton, Oregon.--> | <!--Phil Crosby then and now, with a Tektronix Type 556 and spare CRT at the VintageTEK Museum in Beaverton, Oregon.--> | ||
| Line 98: | Line 110: | ||
[[Oliver Dalton]], [[Bob Rullman]], [[Gene Kauffman]], and [[George Smith]] had done the [[544]], [[546]], and [[547]] mainframes | [[Oliver Dalton]], [[Bob Rullman]], [[Gene Kauffman]], and [[George Smith]] had done the [[544]], [[546]], and [[547]] mainframes | ||
and they felt that the 556 would be a walk in the park. | and they felt that the 556 would be a walk in the park. | ||
Oliver had dreamed up the sweep switching trick for the 547 and felt that a dual beam 'scope should be able to present the same sort of display, | Oliver had dreamed up the sweep switching trick | ||
<ref>In "ALT" sweep mode on a 547, with a compatible plug-in such as a 1A1, input channel A is displayed using the A sweep and input channel B is displayed using the B sweep. This has value when probing two signals that fundamentally operate at different timescales, for example the IF and AF (or video) of a superhet receiver. However, since there is only one beam it is easy to determine when to switch channels in “ALT” mode. | |||
</ref> | |||
for the 547 and felt that a dual beam 'scope should be able to present the same sort of display, | |||
but these people had more important things to do, so the 556 project got handed to the TV group under [[Charlie Rhodes]] in the belief that, | but these people had more important things to do, so the 556 project got handed to the TV group under [[Charlie Rhodes]] in the belief that, | ||
except for the power supply, which would be a difficult packaging job, requiring efficient heat removal, | except for the power supply, which would be a difficult packaging job, requiring efficient heat removal, | ||
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The power transformer had a thick aluminum plate amidst its steel laminations used as a flange to tie to the sides of the two plug-in compartments. | The power transformer had a thick aluminum plate amidst its steel laminations used as a flange to tie to the sides of the two plug-in compartments. | ||
[[File:Tek 556 ps sink.png|thumb|Power transistors (46) mounted on bent aluminum (37) with slots sawn into it. Air flow from the air filter passes through the slots.]] | |||
<!--Power transistors (46) mounted on bent aluminum (37) with slots sawn into it. Air flow from the air filter passes through the slots.--> | <!--Power transistors (46) mounted on bent aluminum (37) with slots sawn into it. Air flow from the air filter passes through the slots.--> | ||
| Line 129: | Line 144: | ||
<!--A pair of 8233 tubes. (temporary photo)--> | <!--A pair of 8233 tubes. (temporary photo)--> | ||
<!--A pair of 8608 tubes. (temporary photo)--> | <!--A pair of 8608 tubes. (temporary photo)--> | ||
[[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.]] | |||
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]], | ||
The seven or eight inches of 93 ohm coaxial cable required a couple of additional time constants to compensate for skin-effect loss. | a PNP germanium transistor that could barely meet the voltage and power dissipation requirements. | ||
<ref> | |||
In the mid-60s, Tektronix had no resident IC design or fabrication facility, | |||
leaving us constrained by the availability of discrete transistors. | |||
The speed, voltage, and power dissipation requirements of the output devices, | |||
together with the need for high writing speed and small spot size always limited the performance of vertical amplifiers. | |||
</ref> | |||
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 | 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=== | |||
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, | ||
| Line 167: | Line 193: | ||
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, | ||
| Line 181: | Line 208: | ||
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, | ||
he said, “I always wondered … “. Some fiddling with currents and time constants diminished the effect. | 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. | |||
===Brought to Market=== | ===Brought to Market=== | ||
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Tek 556 hvps.png | CRT Circuit | Tek 556 hvps.png | CRT Circuit | ||
</gallery> | </gallery> | ||
{{Parts|556}} | |||
[[Category:500 series scopes]] | [[Category:500 series scopes]] | ||
[[Category:Dual beam scopes]] | [[Category:Dual beam scopes]] | ||