7B92: Difference between revisions

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{{Plugin Sidebar   
{{Plugin Sidebar   
|manufacturer=Tektronix  
|manufacturer=Tektronix  
|type=7B92  
|type=7B92
|summary=500 MHz dual timebase  
|summary=500 MHz dual timebase  
|image=7b92a-front.jpg  
|image=Tek 7b92 front.jpg  
|caption=7B92A front  
|caption=7B92 front  
|introduced=1971  
|introduced=1971  
|discontinued=1992
|discontinued=1976
|series=7000-series scopes
|series=7000-series scopes
|designers=Bill DeVey;Les Larson;Val Garuts;Bruce Hofer
|designers=Bill DeVey;Val Garuts
|manuals=
|manuals=
'''7B92'''
'''7B92'''
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* [[Media:070-1192-00.pdf|Tektronix 7B92 Service Manual]] (OCR, uncut schematics)
* [[Media:070-1192-00.pdf|Tektronix 7B92 Service Manual]] (OCR, uncut schematics)
* [[Media:070-1630-00.pdf|Tektronix 7B92 Circuit Description Supplement]]
* [[Media:070-1630-00.pdf|Tektronix 7B92 Circuit Description Supplement]]
'''7B92A'''
* [[Media:070-1752-00.pdf|Tektronix 7B92A Operators Manual -00]] (OCR)
* [[Media:070-1752-01.pdf|Tektronix 7B92A Operators Manual -01]] (OCR)
* [[Media:070-1751-00.pdf|Tektronix 7B92A Instruction Manual -00]] (OCR)
* [[Media:070-1751-02.pdf|Tektronix 7B92A Instruction Manual -02]] (1987 rev., both circuit versions)<small> / [https://bama.edebris.com/download/tek/7b92a-2/tek-7b92a.pdf alternate copy @ BAMA]</small>
}}
}}
The '''Tektronix 7B92''' is a 500 MHz dual timebase plug-in for [[7000-series scopes]].  
The '''Tektronix 7B92''' is a 500 MHz dual timebase plug-in for [[7000-series scopes]].  
It was introduced along with the [[7904]] mainframe in 1972.  In 1976, it was updated as the 7B92A after some abbreviations in the start-up of the fastest sweep rates were discovered due to the original ramp generator design.
It was introduced along with the [[7904]] mainframe in 1972.  In 1976, it was replaced by the [[7B92A]] after some it was discovered that the 7B92's ramp generator had aberrations at the start-up of the sweep at the fastest sweep rates.


According to [[Media:Tekscope 1971 V3 N4 Jul 1971.pdf|July 1971 Tekscope]], it was designed by [[Les Larson]] and [[Bill DeVey]].  On the 7B92A, Larson served as the project engineer and worked on the trigger circuits while [[Bruce Hofer]] designed the sweep generator, delay pickoff, and output amplifier.
According to [[Media:Tekscope 1971 V3 N4 Jul 1971.pdf|July 1971 Tekscope]], the 7B92 was designed by [[Les Larson]] and [[Bill DeVey]].


An "HF Sync" triggering mode is provided in which the trigger level control varies the frequency of a built-in oscillator to lock on to the input for input signals from 100 to 500 MHz, providing higher sensitivity than the direct trigger (which is specified up to 500 MHz as well).
An "HF Sync" triggering mode is provided in which the trigger level control varies the frequency of a built-in oscillator to lock on to the input for input signals from 100 to 500 MHz, providing higher sensitivity than the direct trigger (which is specified up to 500 MHz as well).
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==Internals==
==Internals==
The 7B92 uses a discrete trigger circuit containing [[152-0177-02]] [[tunnel diodes]]. Up to serial number B069999, the 7B92A used a trigger circuit with [[155-0061-00]] amplifiers and [[152-0177-02]] tunnel diodes. After that, the 7B92A used a [[155-0061-00]] trigger amplifier followed by a [[155-0150-00]] trigger detector.
The 7B92 uses a discrete trigger circuit containing [[152-0177-02]] [[tunnel diodes]].


[https://vintagetek.org/years-at-tektronix-hofer/ According to Bruce Hofer], early 7B92 models exhibited sweep anomalies especially near the start of the sweep, and after trying to fix these he convinced management that a redesign was needed.  This resulted in [[Patent US 4009399A]], the [[7B92A]] update, and the [[067-0657-00]] calibration fixture.  
[https://vintagetek.org/years-at-tektronix-hofer/ According to Bruce Hofer],  
early 7B92 models exhibited sweep anomalies especially near the start of the sweep,  
and after trying to fix these he convinced management that a redesign was needed.   
This resulted in [[Patent US 4009399A]], the [[7B92A]] update, and the [[067-0657-00]] calibration fixture.  


The 7B92A uses one other custom IC, the [[155-0049-00|155-0049-xx]] sweep control circuit. The internal jumper for mainframe selection (7800/7900/7100 vs. slower) actually increases the minimum holdoff time on the slower mainframe selection by adding a 214 pF capacitor (C307 for 7B92, C835 for 7B92A) to pin 8 of the sweep control IC [[155-0049-00|155-0049-xx]] in parallel to the existing capacitors. This increases the minimum pulse width of the holdoff signal on [[7000_Series_plug-in_interface|pin B4]] so that the sweep logic of slower mainframes can handle it properly. The effect of this jumper is only noticeable for sweep speeds of 20 μs/Div and faster, since there the smallest shunt capacitance is used on pin 8, and the holdoff time is minimal.
The internal jumper for mainframe selection (7800/7900/7100 vs. slower)  
increases the minimum holdoff time on the slower mainframe selection by adding a 214 pF capacitor, C307,  
to pin 8 of the sweep control IC [[155-0049-00|155-0049-xx]] in parallel to the existing capacitors.  
This increases the minimum pulse width of the holdoff signal on [[7000_Series_plug-in_interface|pin B4]]  
so that the sweep logic of slower mainframes can handle it properly.  
The effect of this jumper is only noticeable for sweep speeds of 20 μs/Div and faster,  
since at those sweep speeds the smallest shunt capacitance is used on pin 8, and the holdoff time is minimal.


==Links==
==Links==
Retrieved from "https://w140.com/tekwiki/wiki/7B92"