PG505

Manuals – Specifications – Links – Pictures

The Tektronix PG505 is a 100 kHz, 80 V pulse generator plug-in for the TM500 system.

The output section is isolated from chassis ground and can float up to ±200 V.

Key Specifications

Period	10 μs to 100 ms in decade steps, one custom position (≥10 μs), variable control ×1 to ×10
Pulse width	5 μs to 50 ms in decade steps, one custom position (≥5 μs), variable control ×1 to ×10
Rise/Fall times	1 μs to 1 ms in decade steps, variable control ×1 to ×20
Amplitude	±4 to min. ±80 V from a 4 kΩ source, floating up to ±200 V to chassis ground (with grounding strap removed, see note)
Duty cycle	min. pulse width to 99%
Input	Delay/Duration, 0 – 10 V into ≥10 kΩ
Gate input	+5 V to inhibit free-running rate generator (rear interface only)
Trigger output	min. +4 V into 10 kΩ / 3 V into 600 Ω, same duration as output

Links

Documents Referencing PG505

Patents that may apply to PG505

Notes

• Manual errata: In manual 070-1583-01, Fig. 4.3 Output Delay Range Check (p. 4-5), the PG 505 connections are drawn correctly but the connector labels are swapped – the left connector fed from the FG501A via the BNC "T" is the Delay/Duration input, not the output. In Table 5-2, Rear Connector Pin Assignments (p. 5-8), pin B7 is incorrectly labeled –33.5 V, it is the NPN pass transistor's collector.
• The PG505 is shipped with the output connector ground connected to chassis ground through a removable ground strap. This must be cut/removed to float the output, in which case output common remains grounded through a 100 kΩ resistor (R545). The manual says this resistor may be removed too, but doing so will cause unspecified "degradation of performance".

Operation

The main controls are a pair of concentric switches for pulse period and pulse duration, with the latter mechanically limited to prevent the duration range to be set higher than the period range. When period and duration switches are in the same position and the variable controls set ×1 (ccw) the output runs at 50% duty cycle.

In the leftmost position of the duration switch, the output is locked in its "on" state so that the amplitude can be set conveniently with a DC voltmeter attached to the output.

The second-rightmost position of either switch is reserved for a custom period or duration that is defined by an optional, customer-installed capacitor for each. Two pairs of test point lugs on the circuit board (near the cam switch cover) are provided to install these capacitors.

In the rightmost position of the period switch ("OUTPUT DELAYED"), the rate generator is disabled. The signal on the Delay/Ext Duration input, assumed to be a positive-going 10 V ramp, is compared to the setting of the Output Delay potentiometer. When the ramp reaches the threshold, an output pulse of the set duration is triggered.

When the duration switch is put in the rightmost position as well (which mechanically forces the period switch to the same), both the rate and duration generator circuits are disabled. In this "EXT DURATION" mode, the output simply follows the Delay/Ext Duration input as compared to the threshold set by the variable delay potentiometer (0−10 V).

Rear Interface

• B27: Trig Out (9A/9B ground)
• B24: Ext Delay In (9A/9B ground)
• B24: Ext Gate In (9A/9B ground)

Family key: Signal source (between pins 23 and 34)

Internals

The rate generator (free-running, discrete) and duration generator (a Fairchild 9601 TTL monoflop) are operating on the chassis-referenced power rails. A small toroidal transformer couples the generated pulse to the output section in the form of differentiated positive and negative pulses.

On the floating side, a Schmitt trigger section restores the square pulse, which steers the output of a pair of current sources via a diode bridge into one of four switch-selected capacitors to create the variable rise and fall time. The output amplifier has a dual FET (2N3958) source follower input.

Two half-wave rectifiers, fed by the series-connected floating 25 V mainframe transformer windings, produce an unregulated floating supply of about ±65 V, from which regulated +48 V, +20 V, –10 V, –10 V, –20 V, and –48 V are derived. Depending on the selected output polarity, either +48 V or –48 V (less an adjustable component) is referenced to output ground. The push-pull output stage therefore has about 96 V supply available.

The output is short-circuit protected by a fixed 4 kΩ series resistor.

Prices

Year	1974	1975	1980	1982
Catalog Price	$265	$295	$550	$840
In 2024 Dollars	$1,700	$1,700	$2,100	$2,700

Pictures

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  Output connector – note ground strap (to chassis lug)

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Examples

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  External Duration mode. 1 kHz Triangle input on CH3, Trig Out on CH2, Output on CH1

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  Same as above, with 0.1 and 10 Hz input