3B5

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Tektronix 3B5
Automatic time base plug-in
Tektronix 3B5 front

Compatible with 560-series scopes

Produced from 1966 to 1972

Manuals
Manuals – Specifications – Links – Pictures

The Tektronix 3B5 is a timebase plug-in for 560-series scopes.

It can be remotely controlled and also has an automatic "seek" mode. It is typically used with a 3A5 vertical plug-in.

Key Specifications

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Links

Documents Referencing 3B5

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Seek Mode

When the 3B5 is put into seek mode, it automatically finds a good sweep speed. The criterion for a sweep speed being good is that it is the slowest sweep such that a second trigger event does not occur before the sweep has progressed beyond a set time window. The time window begins at the start of the sweep and typically extends for three divisions. The "CYCLES/SWEEP" potentiometer controls when the time window ends.

The sweep seek state machine starts with the sweep reset and the sweep speed at its slowest. The trigger is armed and if a signal is present, the sweep begins. If a second trigger event occurs during the time window, the sweep is considered too slow. In that case, the sweep speed is incremented to the next faster setting. If the sweep gets beyond the window without a second trigger event occurring, the sweep is considered good, and the sweep seek state machine stops. When the sweep seek state machine is stopped, the scope operates in normal mode, i.e., waiting for trigger, sweeping, resetting, and waiting for trigger in an endless loop.

For example, say the 3B5 window is three divisions and the input signal is a 1 kHz square wave, and rising edge triggering is selected. The user engages SEEK mode.

  1. The sweep seek state machine sets the sweep speed to 5 sec/div. Three divisions at 5 sec/div is 15 seconds, so the time window begins at the rising edge event that caused the sweep to start, and ends 15 seconds after the that event. The second rising of the 1 kHz occurs after 1 ms, so it occurs within the time window. Therefore, the sweep speed is advanced to 2 sec/div.
  2. At 2 sec/div, the window is 6 seconds. 1 ms < 6 seconds; sweep speed is advanced to 1 sec/div.
  3. At 1 sec/div, the window is 3 seconds. 1 ms < 3 seconds; sweep speed is advanced to 0.5 sec/div.
  4. At 0.5 sec/div, the window is 1.5 seconds. 1 ms < 1.5 seconds; sweep speed is advanced to 0.2 sec/div.
  5. At 0.2 sec/div, the window is 0.6 seconds. 1 ms < 0.6 seconds; sweep speed is advanced to 0.1 sec/div.
  6. At 0.1 sec/div, the window is 0.3 seconds. 1 ms < 0.3 seconds; sweep speed is advanced to 50 ms/div.
  7. At 50 ms/div, the window is 150 ms. 1 ms < 150 ms; sweep speed is advanced to 20 ms/div.
  8. At 20 ms/div, the window is 60 ms. 1 ms < 60 ms; sweep speed is advanced to 10 ms/div.
  9. At 10 ms/div, the window is 30 ms. 1 ms < 30 ms; sweep speed is advanced to 5 ms/div.
  10. At 5 ms/div, the window is 15 ms. 1 ms < 15 ms; sweep speed is advanced to 2 ms/div.
  11. At 2 ms/div, the window is 6 ms. 1 ms < 6 ms; sweep speed is advanced to 1 ms/div.
  12. At 1 ms/div, the window is 3 ms. 1 ms < 3 ms; sweep speed is advanced to 0.5 ms/div.
  13. At 0.5 ms/div, the window is 1.5 ms. 1 ms < 1.5 ms; sweep speed is advanced to 0.2 ms/div.
  14. At 0.2 ms/div, the window is 0.6 ms. 1 ms > 0.6 ms; sweep speed stays at 0.2 ms/div.

Pictures

3B5

3B5 Prototype

Components

Some Parts Used in the 3B5

Part Part Number(s) Class Description Used in
12BY7A 154-047 154-0047-00 Vacuum Tube (Pentode) miniature 6.5 W power pentode 106 163 524 531 533 535 536 541 543 535 545 545A 549 555 75 3A75 3B5
1N3717 152-0381-00 152-0125-00 Discrete component 4.7 mA, 25 pF tunnel diode 1L40 1S1 1S2 11B1 11B2 11B2A 147A 1470 148 21A 22A 3B4 3B5 408 432 434 453 453A 454 466 491 5T3 544 RM544 546 RM546 547 RM547 556 RM556 7B70 7B71 7D11
6AL5 154-016 154-0016-00 154-0038-00 Vacuum Tube (Dual Diode) high-perveance dual diode 163 181 190 1M1 310 310A 315 316 317 3B1 3B1S 3B2 3B3 3B5 502 502A 503 511 511A 512 516 517 517A 524 526 535 535A 545 545A 549 551 565 570 581 581A 585 585A C T Telequipment D52 Telequipment D56 Telequipment S52
7119 154-0340-00 Vacuum Tube (Dual Triode) dual triode 067-0532-00 191 3A3 3B4 3B5 516 545B 549 661 Chemtrix 205
7586 154-0306-00 Vacuum Tube (Triode) Nuvistor triode M 1A1 1A2 1A5 10A2 10A2A 11B1 11B2A 321 321A 3A1 3A1S 3A3 3A5 3A6 3A7 3A8 3A74 3S76 3T77 3T77A 3B5 4S1 4S2 6R1 6R1A 9A1 9A2 82 86 S-311
STD704 152-0125-00 Discrete component 4.7 mA tunnel diode 1L40 1S1 11B1 11B2 11B2A 147 R147 147A R147A 1470 148 R148 148-M 149 R149 149A R149A 21A 22A 3B4 3B5 408 432 434 453 453A 454 464 465 466 491 5T3 544 RM544 546 RM546 547 RM547 556 RM556 7B70 7B71 7D11
STD962 152-0169-00 Discrete component 1 mA, 10 pF tunnel diode L140 Pentrix L20 Pentrix L30 067-0518-00 067-0594-00 1L60 1S2 1503 3B5 3T7 4054 4054A 4902 5S14N 7S14 7T11