TG501

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

• Option 01 adds a 5MHz tempature-compensated crystal oscillator (Y50), and a TTL decade counter (U50) for a stable, precise internal clock.

Manuals – Specifications – Links – Pictures

There is also a TG501A.

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

Key Specifications

Interval	1 ns to 5 s in 1−2−5 sequence
Timing accuracy	Stability 1×10-5, long-term drift 1×10-5 per month (with Option 1, 5×10-7 / 1×10-7 per month)
Error Readout	Accuracy 1 digit (±0.1% points), Range to ±7.5%
Amplitude	≥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) (all into 50 Ω)
Trigger Output	Slaved to marker output from 5 s through 100 ns. Remains at 100 ns for all faster markers
External Reference Input	1 MHz, 5 MHz or 10 MHz; TTL compatible (internally hard wired so output frequencies counted down to 1 MHz)

Rear Interface Signals

Connector Pin		Description
Signal	Return
28A	27A	Marker Out (requires front BNC disconnection)
27B	28B	Trigger Out (requires front BNC disconnection)
25A	26A	Internal 1 MHz Clock Out (TTL)
24B	25B	External Clock Input
26B	22B	Data Good (High when BCD data valid)
17A..20A	22B	bit 4..1 BCD Display data, MSD
21A..24A	22B	bit 4..1 BCD Display data, LSD
16A	22B	Fast=Low, Slow=High

Internals

The TG501 internally produces a 1 MHz reference clock, either from an internal crystal oscillator, or from an externally supplied frequency.

A 100 MHz VCO is phase-locked to this reference frequency (in fixed-frequency mode) or to the output of a variable 1 MHz astable multivibrator (in variable frequency mode). When the variable oscillator is in use, its frequency is digitally compared to the fixed 1 MHz reference and displayed as a deviation in percent with a pair of LEDs indicating the sign (fast or slow).

A chain of dividers running off the 100 MHz clock provide the selectable output markers.

The 1 ns output uses a step recovery diode (HP 5082-8872, part 152-0503-00).

Links

• See the TG501/Repairs page for repair information.
• Tek TG501A Time Mark Gen Restoration by NFM @ YouTube
• TG501 Repair and Calibration by Zenwizard Studios @ YouTube
• TG501 In-Depth Troubleshooting of a Stubborn Unit by Zenwizard Studios @ YouTube
• TG501 In-Depth Troubleshooting of a Stubborn Unit Part 2 by Zenwizard Studios @ YouTube
• Tektronix TG501A Refresh and Check For a Viewer by Zenwizard Studios @ YouTube

Prices

Year	1975
Catalog Price	$745
In 2023 Dollars	$4,300

Pictures

TG501

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  TG501 early version

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  TG501 late version

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  TG501 early version

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  TG501 early version

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  TG501 output waveform

TG501A

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Parts

Some Parts Used in the TG501

Part	Part Number(s)	Class	Description	Used in
152-0503-00	152-0503-00	Discrete component	500 ps step recovery diode	1503C • TG501 • TG501A
Signetics N8T06B	156-0379-00	Monolithic integrated circuit	7-segment driver	TG501

Some Parts Used in the TG501A

Part	Part Number(s)	Class	Description	Used in
152-0503-00	152-0503-00	Discrete component	500 ps step recovery diode	1503C • TG501 • TG501A