7B92 - TekWiki
- ️Mon Oct 07 1968
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. According to 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).
Internal jumpers are provided to configure the 7B92 for operation in 7800/7900 vs. slower mainframes, and to select whether the variable control affects the delaying or the delayed time base.
As a dual time base, the 7B92 uses the top field in the display readout for the sweep speed of the main and the bottom field for the delayed time base. The delay time can only be read from the 10-turn analog dial.
The 7B92 has no magnifier function but its regular sweep dial setting reaches down to 500 ps/Div. It has no provision for X-Y operation.
Key Specifications
| Sweep speed | 0.5 ns/Div to 0.2 s/Div, 1−2−5 sequence (variable up to 0.5 s/Div) |
|---|---|
| Delay time | 0 to 9.9 Div |
| Triggering | 0.5 Div or 100 mV up to 20 MHz, 1 Div or 500 mV up to 600 MHz |
| Jitter | < 50 ps at 600 MHz |
| Ext Trig input | 1 MΩ // 20 pF or 50 Ω |
After the 7B92 had been in production for years, it was discovered that the 7B92's ramp generator had aberrations at the beginning of the sweep at the fastest sweep rates. Bruce Hofer recalls investigating this issue and concluding that an redesign was needed. The redesign led to the introduction of the 7B92A, Patent US 4009399A, and the 067-0657-00 calibration fixture.
Links
Documents Referencing 7B92
Document
Class
Title
Year
Links
Tekscope 1971 V3 N4 Jul 1971.pdf
Article
A Subnanosecond Realtime Oscilloscope
Val Garuts • Thor Hallen
1971
7904 • 154-0644-00 • 7A19 • Ft doubler • 7B92
7000 series brochure March 1973.pdf
Brochure
7000 series brochure, March 1973
1973
7A11 • 7A12 • 7A13 • 7A14 • 7A15A • 7A16A • 7A17 • 7A18 • 7A19 • 7A21N • 7A22 • 7B50 • 7B53A • 7B70 • 7B71 • 7B92 • 7CT1N • 7D11 • 7D13 • 7D14 • 7D15 • 7M11 • 7L12 • 7S11 • 7S12 • 7T11 • 7704A • R7704 • 7904 • R7903 • 7603 • R7603 • 7403N • R7403N • 7313 • R7313 • 7613 • R7613 • 7623 • R7623 • P7001
Patents that may apply to 7B92
Internals
The 7B92 uses a discrete trigger circuit containing 152-0177-02 tunnel diodes.
The internal jumper (J308/J309) for mainframe selection (7800/7900/7100 vs. slower) increases the minimum holdoff time on the slower mainframe selection by adding a 150 pF capacitor, C307, to pin 8 (HO TIMING) of the sweep control IC, U310 (155-0049-xx), in parallel to the existing capacitors. This increases the minimum pulse width of the holdoff signal on 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.
Pictures
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7B92 front
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7B92 right
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7B92 left
Components
Some Parts Used in the 7B92
Part
Part Number(s)
Class
Description
Used in
155-0061-00
155-0061-00 • 155-0061-01 • 155-0061-02
Monolithic integrated circuit
trigger amplifier
7B92 • 7B92A
1N3719
152-0182-00
Discrete component
10 mA, 50 pF germanium tunnel diode
422 • 661 • 7B92 • 7B92A
SMTD998
152-0177-02
Discrete component
10 mA, 2 pF tunnel diode
067-0681-01 • 485 • 7B92 • 7B92A