Tektronix TG501 Time Mark Generator

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*NOTE - 2 STYLES ***

Quick Specifications / Photos
List of Options
Detailed Specifications
Operating Instructions
Misc. Part Numbers

Samples of e-Bay Prices
Orig CostLow BidHigh Bidaverage
$995 (1977)
$1810 (1982)
$2175 (1985)
$187.50 8/3/01 #1621338569 bbg
$211.00 8/4/01 #1622941061 calibrationlab
$no bids (asked $79.99) 8/13/01 #1647062496 calibrat1
$51.00 10/25/01 #1651960593 calibrat1
$203.49 11/2/01 #1655301516 del1935
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$98.54 11/13/01 #1660141354 abeja
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$82.00 1/20/02 #1690242353 hitekkey
$76.66 1/20/02 #1690387985 bae9259
$102.50 1/27/02 #1694736881 fallen-idc
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$99.00 2/22/02 #1706415411 bbg
No Buy ($77 < reserve) 2/24/02 #1706837239 techcycle
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$76.35 4/14/02 #1721296980 fallen-idc
$113.50 7/7/02 #1745806400 carpetas
$127.49 7/14/02 #1748019346 imacollector (opt 1)
$155.00 1/21/03 #3108026237 testequipment (tested-no 1ns sig) (7 bids $50 start)
$49.99 1/28/03 #3109886447 sales@astglobal.com (untested-old style) (1 bid)
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$66.99 2/4/06 #7585846500 andpower79 (8 bids $3.99 start) (worked but untested)
$113.50 4/14/06 #7608094493 mooshak1 (6 bids $20 start) (new style - untested)
$37.00 (+$12 ship) 1/6/08 #280189273188 surplusauctions (9 bids $4.99 start) (old style - untested)

  • Marker Outputs, 5 s to 1 ns
  • Direct Readout of Oscilloscope Timing Error
  • External Trigger Output

    Option 01 = More Accurate 5 MHz Time Base

    The TG 501 Time Mark Generator provides marker outputs from five seconds to one nanosecond. A unique feature on the TG 501 is a variable timing output with a front-panel two-digit LED display which indicates percentage of timing error between the normal time interval and a variable interval set to line up the marker pulse with graticule or division mark on the display. This feature not only provides direct readout in terms of percent error, but also helps eliminate errors associated with visually estimating error from a display. Since many specifications are given in percentages, the error readout eliminates the need for computations and, additionally, lessens parallax discrepancies.

    Marker selection from 5 s through 10 ns in a 1, 2, 5 sequence is selected by a rotary switch. 5, 2, and 1 ns modified sine waves are selected by self-cancelling push-buttons when the rotary switch is in the 521N position.

    CharacteristicsPerformance RequirementsSupplemental Information
    Markers1 ns through 5 s in a 1-2-5 sequence.5 s through 10 ns are selected by a rotary switch. 5 ns, 2 ns, and 1 ns are pushbutton selected modified sine waves
    Marker Amplitude≥1 V peak into 50 Ω on 5 s through 10 ns markers.
    ≥750 mV peak into 50 Ω on 5 ns and 2 ns markers.
    ≥200 mV peak into 50 Ω on 1 ns marker.
    Trigger Output SignalSlaved to marker output from 5 s through 100 ns. Remains at 100 ns for all faster markers.
    Internal ReferenceStandardOption 1
    Crystal Frequency1 MHz5 MHz
    Stability (0° to 50°C) after ½ hour warm-upwithin 1 part in 105within 5 parts in 107
    Long-term Drift1 part or less in 105 per month1 part or less in 107 per month
    AccuracyAdjustable to within 1 part in 107Adjustable to within 5 parts in 109
    External Reference Input (Available Only if U50 and jumpers are installed and U100 is removed) IC and jumpers for 5 or 10 MHz. 1 MHz external reference requires jumpers only
    Acceptable Frequencies1 Mhz, 5 Mhz, or 10 MHzInternally hard wired so output frequencies counted down to 1 MHz
    Input AmplitudeMust be TTL compatible
    Error Readout RangeTo ±7.5%
    Error Readout ResolutionTo 0.1%Least significant digit counted is 0.01% and is rounded off between 5 and 6 providing a more accurate error readout resolution (±0.07% of Least Significant Digit)

    External Reference InputAvailable with internal changes. Acceptable frequencies, 1 MHz, 5 MHz, or 10 MHz. Input amplitude must be TTL compatible.
    Time Error Readout RangeTo ±7.5%
    Timing Error Measurement AccuracyDevice under test error is indicated to within one least significant digit (to within one displayed count).

    above excerpt from 1977 TM500 Instruments Brochure


    Operating Considerations

    The internal reference of the TG 501 is a 1 MHz crystal. If Option 1 is installed, a high accuracy 5 MHz crystal is provided. Provisions are made for buffered output of either 1 MHz or 5 MHz internal clock through interface connector pin 25A with associated ground on pin 26A.

    A 1 MHz, 5 MHz or 10 MHz external clock can be substituted. To use an external 5 or 10 MHz clock, U50 must be installed and the necessary jumpers added to divide down the input to meet the 1 MHz internal requirement. U50 is not required for a 1 MHz external clock, but jumpers must still be added.


    Calibrated Mode

    When the center-button of VARIABLE TIMING Control is pushed in, the MARKER Control selects calibrated marker intervals from 5 s to 10 ns indicated by the lighted knob skirt. To select 5, 2 or 1 ns modified sine wave markers, set MARKER Control to 521N position and depress desired pushbutton.

    Variable Timing Mode

    When the center button of VARIABLE TIMING Control is out, output timing is faster or slower than the calibrated marker to the percentage indicated by the VARIABLE TIMING READOUT Display and the FAST-SLOW Indicator lights. 5, 2 and 1 ns push-button controlled modified sine waves are not variable and Readout Display is turned off when MARKER Control is in 521N position.

    Readout Display Test

    To check the operation of the display LED's (Light-Emitting Diodes), fully depress the center button of the VARIABLE TIMING Control (push in firmly). All LED segments should light, displaying 8.8 in the Readout.


    The TG 501 can be3 used for many applications not described in the manual. Use the following examples to become familiar with the TG 501's VARIABLE TIMING READOUT.

    Time Base Measurements

    To accurately determine the timing error of a time base:

    1. Connect the MARKER OUT of the TG 501 to the Vertical Input of the oscilloscipe. Use a 50Ω coaxial cable terminated into 50Ω.

    2. Connect the TRIGGER OUT of the TG 501 to the External Trigger Input of the time base. Use a 50Ω coaxial cable terminated into 50Ω.

    3. Selct external trigger source on the time base.

    4. Select, for example, 1 μs sweep rate of the time base.

    5. Set MARKER Control rotary switch of TG 501 to 1 μs.

    6. Make sure center button of VARIABLE TIMING Control, concentric with MARKER Control, is out (Variable Timing Mode).

    7. Use Horizontal Position control of time base to make first time mark coincide with first graticule line on the oscilloscope.

    8. Rotate VARIABLE TIMING knob until all time markers coincide with graticule lines on the oscilloscope.

    9. Either the FAST or SLOW Indicator will light showing whether the time base is faster or slower than the calibrated markers of the TG 501. Read the percentage of error from the VARIABLE TIMING READOUT Display.

    Pulse Generator Measurements

    To accurately determine pulse duration or period of a Pulse Generator.

    1. A dual-trace vertical oscilloscope is required. Select alternate mode.

    2. Connect the MARKER OUT of the TG 501 to one channel of the dual-trace oscilloscope. Use a 50Ω coaxial cable terminated into 50Ω.

    3. Connect the Output of the pulse generator to the other channel of the dual-trace oscilloscope, using a 50Ω coaxial cable terminated into 50Ω.

    4. Set the time/div switch to display 1 cycle of a pulse in 10 divisions of the graticule on the oscilloscope.

    5. Use the MARKER Control switch of the TG 501 to display one time marker approximately at pulse duration and one at pulse period. Align first time marker with beginning of pulse wveform.

    6. Select Variable Timing Mode on the TG 501. VARIABLE TIMING Control center button out.

    7. Use the Vertical Position control of the oscilloscope to set the peaks of the time markers at 50% amplitude of pulse.

    8. To fcheck the timing of pulse duration, rotate the VARIABLE TIMING knob until time marker coincides with pulse duration.

    9. Either the FAST or SLOW Indicator will light, showing whether the pulse duration of the pulse generator is faster or slower than the calibrated time mark of the TG 501. Read the percentage of orror from the VARIABLE TIMING READOUT Display.

    10. To check the timing of pulse period, rotate the VARIABLE TIMING knob until time marker coincides with pulse period.

    11. Read the VARIABLE TIMING READOUT Display and check the FAST-SLOW Indicators as described in step 9 to find the percentage of error from standard timing.

    above excerpt from TG 501 TIME MARK GENERATOR Instruction Manual

    1-2366-1166-00Knob : Gray (w/red-small inner) (variable timing)
    1-3366-1509-00Knob : Gray w/ Skirt (Outer) (Marker (SEC))
    1-7366-1489-33 Push Button : 5NS
    1-8366-1489-34Push Button : 2 NS
    1-9366-1489-35Push Button : 1 NS
    1-32260-1571-00Switch, Push (Centralab 2KBC030000-XXX) (5ns,2ns,1ns)
    1-49 (R135-older)311-1416-00Res.,Var,Nonwir : 200 ohm,20%,1W (A-B 10M417A) (variable)
    1-49 (R135-newer)311-0169-00Res.,Var,Nonwir : 100 ohm,20%,0.5W (A-B W7564B) (variable)