3T77A
The Tektronix 3T77A is a sampling sweep plug-in for 560-series scopes, introduced in 1966 as a facelift version of the 3T77.
Key Specifications
| Sweep rate | 0.2 ns/div to 10 μs/div (1–2–5); ×10 magnifier |
|---|---|
| Sweep Input | 5 to 25 V/div into 28 to 100 kΩ |
Links
Documents referencing 3T77A
| Document | Class | Title | Authors | Year | Links |
|---|---|---|---|---|---|
| Service Scope 52 Oct 1968.pdf | Article | The State of the Art in Sampling | Al Zimmerman | 1968 | S-1 • S-2 • S-3 • S-4 • S-50 • S-51 • 285 • 3S1 • 3S2 • 3S5 • 3S6 • 3T2 • 3T5 • 3T6 • 3T77A • 568 • 230 |
Patents that may apply to 3T77A
| Page | Title | Inventors | Filing date | Grant date | Links |
|---|---|---|---|---|---|
| Patent US 3317743A | Pulse generator circuit | John V Rogers | 1962-06-11 | 1967-05-02 | Sampling • 3T77 • 3T77A |
| Patent US 3359429A | Trigger generator circuit having synchronized astable input oscillator | Henry A Zimmerman | 1964-03-23 | 1967-12-19 | Sampling • 3T77 • 3T77A |
Differences to 3T77
The Horizontal Magnifier is replaced with a Time Expander, and the Delay control with a Time Position control. The Time Expander provides display expansion without decreasing the display dot density (dots/div), and the Time Position control provides display positioning that is commensurate with the sweep rate used, rather than a fixed-range delay. This permits the display to be positioned through at least one screen diameter on all equivalent sweep rates.
The Recovery Time knob can be pulled for synchronizing to input signals between 30 MHz and 1 GHz.
Operation
The 3T77 can trigger on either the internal trigger pick-off from the vertical plug-in, or on an external trigger signal input. Triggering is faster and more sensitive with an external input.
The 3T77 can operate in any of four modes: external sweep, manual sweep, normal, or single sweep.
In external sweep mode, an external control voltage is applied to a BNC connector on the front panel of the 3T77. This voltage determines the X-position of the spot on the CRT and, correspondingly, the delay from the trigger event to the sampling point.
Manual mode is the same as external sweep mode, but the control voltage is generated internally based on the position of a potentiometer on the front panel of the 3T77.
In normal mode, an internal ramp generator produces the control voltage, repeatedly redrawing the trace on the CRT. In single sweep mode, the internal ramp generator is started by a button on the front panel, makes one horizontal trace, and then waits for the button to be pressed again.
Prices
| Year | Catalog price | In 2026 dollars |
|---|---|---|
| 1966 | $650 | ~$6,600 |
| 1969 | $700 | ~$6,300 |
| 1971 | $900 | ~$7,300 |
Pictures
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3T77A Front
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3T77A Left
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3T77A Right
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3T77A Trigger Board
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3T77A Trigger Board
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3T77A Top
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3T77A Rear
Components
Some Parts Used in the 3T77A
- SN 5506+: 152-0380-00 replacing 152-0043-00 (D25,D42,D93)
- SN 5650+: 152-0387-00 replacing 152-0203-00 (D22)