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Tektronix TG501
time mark generator
Tektronix TG501

Compatible with TM500 system

Produced from 1974 to 1995

Manuals – Specifications – Links – Pictures

The Tektronix TG501 is a time mark generator plug-in for the TM500 system.

Note the output must be terminated into 50 Ω or there may be no signal at all.

There is also a TG501A.


  • Markers: 5 s to 1 ns in a 1,2,5 sequence
  • Marker Amplitude (into 50 Ω): ≥1 V peak on 5 s through 10 ns; ≥750 mVp-p on 5 ns and 2 ns; ≥200 mVp-p on 1 ns (separate output)
  • Trigger Output Signal: Slaved to marker output from 5 s through 100 ns. Remains at 100 ns for all faster markers
Internal Reference Standard (1 MHz) Option 1 (5 MHz)
Stability 1E-5 5E-7
Long-Term Drift 1E-5 per month 1E-7 per month
Setability 1E-7 5E-9
  • External Reference Input: 1 MHz; 5 MHz; 10 MHz; TTL compatible (internally hard wired so output frequencies counted down to 1 MHz)
  • Error Readout Range: to ±7.5%
  • Error Readout accuracy: One digit (±0.1%-points)
  • Net Weight: 1 kg
  • Dimensions: 66.8 mm × 285.3 mm × 125.9 mm (w/d/h)

Repair Issues

  • Check for +15 V and adjust if not between 14.3 V and 15.7 V
  • If +5 V is outside 4.94 V − 5.46 V, check U626 (LM741) − old opamps are prone to failure.
  • A lot of ICs are placed in non gold plated IC sockets. Contact problems can occur. Removing and inserting ICs helps.
  • A1 board should be mounted to frame only with washers inbetween, especially near the rear connector. Shorts to conductor tracks can occur otherwise.