The Tektronix Type 5T3 is a timing plug-in for the Type 661 sampling oscilloscope. It uses TD253B tunnel diodes for triggering.

Tektronix 5T3
Timing plugin
Tek 5T3

Compatible with 661

Produced from 1965 to (?)

(All manuals in PDF format unless noted otherwise)

The 5T3 can be triggered from any of four different sources:

  1. Internal trigger from the sampling plug-in, via interconnect J9.
  2. Internal trigger from the calibrator module in the 661 mainframe. This works up to 1 GHz.
  3. External trigger to the high-impedance BNC trigger input. This input is buffered by an 8056 Nuvistor cathode follower. This can be used for triggering on signals up to 20 MHz.
  4. External trigger to the 50 Ω GR-874 trigger input. This input can drive either of two selectable signal paths:
    • A path where the trigger signal skips the high-impedance Nuvistor input buffer but is still buffered by Q64 and Q124 (1 GHz NPN transistors, part number 151-0138-00) before the tunnel diode trigger event recognizer circuit. This path provides triggering up to 500 MHz.
    • A passive low-impedance path, capacitively coupled to a tunnel diode for "UHF SYNC" mode. This works up to 5 GHz.

The 5T3 can also be set to free-run mode.

Key Specifications

  • please add


Documents Referencing 3S3



Some Parts Used in the 5T3

Part Part Number(s) Class Description Used in
151-0108-00 151-0108-00 Discrete component 350 MHz (minimum) NPN bipolar transistor 5T3
151-0138-00 151-0138-00 Discrete component 1 GHz (minimum) NPN bipolar transistor 5T3
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
8056 154-0417-00 Vacuum Tube (Triode) low-voltage Nuvistor triode 422 502 W 1S1 3A7 3S3 3T4 5T3 10A1
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