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{{TM500 | mfg=Tektronix | type=TG501 | function=time mark generator | class=pulse generator | image=Tek tg501 on.JPG | introduced=1974 | discontinued=1995 |
{{TM500 | mfg=Tektronix | type=TG501 | function=time-mark generator | class=pulse generator | image=Tek tg501 on.JPG | introduced=1974 | discontinued=1995 |
manuals=
manuals=
* [http://w140.com/smb/TG501_SM.pdf Tektronix TG501 Manual (OCR, PDF)]
'''TG501'''
* [[Media:TG501 schematics.pdf|Tektronix TG501 Schematics (stitched, PDF)]]
* [[Media:070-1576-00.pdf|TG501 Manual 070-1576-00]]
* [[Media:070-1576-02.pdf|TG501 Manual 070-1576-02]] (OCR, stitched schematics)
 
* [[Media:050-1425-02.pdf|TG501 Product Mod 050-1425-02]]
* [[Media:TG501 schematics.pdf|TG501 Schematics, stitched]]
 
'''TG501A'''
* [[Media:070-7373-00.pdf|TG501A Manual 070-7373-00]]
}}
}}
* Option 01 adds a 5MHz tempature-compensated crystal oscillator (Y50), and a TTL decade counter (U50) for a stable, precise internal clock.
There is also a TG501A.


Note the [http://www.eevblog.com/forum/repair/tektronix-tg501-out-put-problem/ output must be terminated into 50 Ω] or there may be no signal at all.
Note the [https://www.eevblog.com/forum/repair/tektronix-tg501-out-put-problem/ output must be terminated into 50 Ω] or there may be no signal at all.


There is also a TG501A.
{{BeginSpecs}}
{{Spec | Interval                | 1 ns to 5 s in 1−2−5 sequence }}
{{Spec | Timing accuracy          | Stability 1×10<sup>-5</sup>, long-term drift 1×10<sup>-5</sup> per month (with Option 1, 5×10<sup>-7</sup> / 1×10<sup>-7</sup> per month) }}
{{Spec | Error Readout            | Accuracy 1 digit (±0.1% points), Range to ±7.5% }}
{{Spec | Amplitude                | ≥1 V peak on 5 s through 10 ns; ≥750 mV<sub>p-p</sub> on 5 ns and 2 ns; ≥200 mV<sub>p-p</sub> on 1 ns (separate output) (all into 50 Ω) }}
{{Spec | Trigger Output          | Slaved to marker output from 5 s through 100 ns. Remains at 100 ns for all faster markers }}
{{Spec | External Reference Input | 1 MHz, 5 MHz or 10 MHz; TTL compatible (internally hard wired so output frequencies counted down to 1 MHz) }}
{{EndSpecs}}


==Specifications==
==Rear Interface Signals==
* Markers: 5 s to 1 ns in a 1,2,5 sequence
<small>
* Marker Amplitude (into 50 Ω): ≥1 V peak on 5 s through 10 ns; ≥750 mV<sub>p-p</sub> on 5 ns and 2 ns; ≥200 mV<sub>p-p</sub> on 1 ns (separate output)
{| class="wikitable"
* Trigger Output Signal: Slaved to marker output from 5 s through 100 ns. Remains at 100 ns for all faster markers
|-
:{| class="wikitable"
! colspan="2" | Connector Pin
! Internal Reference !! Standard (1 MHz) !! Option 1 (5 MHz)
! rowspan="2" | 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
|-
|-
| Stability || 1E-5 || 5E-7
| 26B      || 22B || Data Good (High when BCD data valid)
|-
|-
| Long-Term Drift || 1E-5 per month || 1E-7 per month
| 17A..20A || 22B || bit 4..1 BCD Display data, MSD
|-
|-
| Setability || 1E-7 || 5E-9
| 21A..24A || 22B || bit 4..1 BCD Display data, LSD
|-
| 16A      || 22B || Fast=Low, Slow=High
|}
|}
* External Reference Input:  1 MHz; 5 MHz; 10 MHz; TTL compatible (internally hard wired so output frequencies counted down to 1 MHz)
</small>
* 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==
==Internals==
* Check for +15 V and adjust if not between 14.3 V and 15.7 V
The TG501 internally produces a 1 MHz reference clock, either from an internal crystal oscillator, or from an externally supplied frequency.
* 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.
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).
* A1 board should be mounted to frame only with washers inbetween, especially near the rear connector. Shorts to conductor tracks can occur otherwise.
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.
* [https://www.youtube.com/watch?v=U5LQpqwqNIU Tek TG501A Time Mark Gen Restoration] by NFM @ YouTube
* [https://www.youtube.com/watch?v=FIe9WzdIZ9g TG501 Repair and Calibration] by Zenwizard Studios @ YouTube
* [https://www.youtube.com/watch?v=rF5V7D0VZeE TG501 In-Depth Troubleshooting of a Stubborn Unit] by Zenwizard Studios @ YouTube
* [https://www.youtube.com/watch?v=1t7ndiKzYI8 TG501 In-Depth Troubleshooting of a Stubborn Unit Part 2] by Zenwizard Studios @ YouTube
* [https://www.youtube.com/watch?v=yl29OOxyNf0 Tektronix TG501A Refresh and Check For a Viewer] by Zenwizard Studios @ YouTube
{{Documents|Link=TG501}}
 
==Prices==
{| class="wikitable sortable"
|-
! Year
! 1975
|-
! Catalog Price
| align="right" | $745
|-
! In 2023 Dollars
| align="right" | $4,300
|}


==Pictures==
==Pictures==
===TG501===
<gallery>
Tek tg501 on.JPG          | TG501 early version
Tg 501 late.jpg          | TG501 late version
Tek tg501 internal1.jpg
Tek tg501 internal2.jpg
Tek tg501 internal3.jpg
Tek tg501 internal4.jpg
Tek tg501 internal5.jpg
Tek tg501 internal6.jpg
Tek tg501 internal7.jpg
Tek tg501 early left.jpg  | TG501 early version
Tek tg501 early right.jpg | TG501 early version
Tek tg501 waveform.jpg    | TG501 output waveform
</gallery>


===TG501A===
<gallery>
<gallery>
Tek tg501 on.JPG|TG501 Early Version
Tek tg501a.jpg
Tg 501 late.jpg|TG501 Late Version
Tek tg501a.jpg|TG501A
Tek tg501 waveform.jpg
Tek tg501 internal1.jpg|TG501
Tek tg501 internal2.jpg|TG501
Tek tg501 internal3.jpg|TG501
Tek tg501 internal4.jpg|TG501
Tek tg501 internal5.jpg|TG501
Tek tg501 internal6.jpg|TG501
Tek tg501 internal7.jpg|TG501
Tek tg501 early left.jpg|TG501 early version
Tek tg501 early right.jpg|TG501 early version
</gallery>
</gallery>


[[Category:Time mark generator]]
==Parts==
{{Parts|TG501}}
{{Parts|TG501A}}
 
[[Category:Time mark generators]]
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