PG508

The Tektronix PG508 is a 50 MHz pulse generator plug-in for the TM500 system.

Manuals – Specifications – Links – Pictures

It was designed by Fred Beckett, Dennis Feucht, Tom Hill, and Gary Kersey.

Pulses can be triggered by an external input, a manual trigger button, or an internal period generator (optionally gated by the trigger input). The trigger signal can be undelayed, delayed by a selectable time, or both (in which case double pulses are generated). The pulse duration, leading and trailing edge transition times, high- and low-level amplitude can be controlled independently.

Period, delay, duration, and transition time switches each feature a custom position where a user-supplied internal capacitor determines the timing.

Key Specifications

Period	external, or internal <20 ns to >200 ms in 7 decade steps plus variable; ≥200 ms possible in custom range
Jitter	<0.1% +50 ps
Delay Time	<10 ns to >100 ms in 7 decade steps plus custom position and variable control; ≥100 ms possible in custom range
Pulse Duration	square, or <10 ns to >100 ms in 7 decade steps plus custom position and variable control; ≥100 ms possible in custom range
Transition time	Ranges 5 ns to 500 μs in decade steps plus custom position; separate  ×1 to ×100 variable controls for leading and trailing edge (5 ns to 50 ms effective)
Output level	High and low levels adjustable independently in −20 V to +20 V range, limited to max. 20 Vp-p / min. 1 Vp-p (open circuit), 50 Ω source impedance (−10 V to +10 V, 0.5 to 10 Vp-p into 50 Ω)
Trigger/Gate input	Sensitivity 80 mVp-p to ≥10 MHz, 250 mVp-p to ≥50 MHz at 50 Ω impedance, max. ±5 Vpeak; 1 MΩ // 20 pF optionally selectable (internal switch), max. ±20 Vpeak

Rear Interface

(on right-hand plug-in slot as viewed from front)

Connector Pin		Description
Signal	Return
27B	28B	Trig output (complement polarity installed; for normal polarity, front panel input requires optional cable and front output disconnection) [note error on manual page 1-12; table 1-13 is correct]
24B	25B	Trig input (with optional cable, front panel input must be disconnected)
25A	26A	Amplitude Monitor (from output via 27 kΩ)
22A		External Low Level Control Input (requires internal jumper and trim)
22B		External High Level Control Input (requires internal jumper and trim)

Custom connection solder pads are available on the left plug-in slot, which is otherwise used only for the associated pass transistors in the mainframe.

References

• Designs by the Masters – ±20 V, 5 ns, 50 Ω Amplifier (detailed discussion of the PG508 output stage). Horowitz & Hill, Art of Electronics − The x-Chapters, p.150+
• Don Hall, A 50 MHz pulse generator with variable transition times. Tekscope V.8 N.1 1976, p.13+

Links

• PG508 Repair and Calibration by Zenwizard Studios @ YouTube

Pictures

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  Output board (The black coax connection from the output stage to the left plug-in slot is non-standard.)

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Custom ICs used in the PG508