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Tektronix CFG253, Процедуры обслуживания

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CFG253

Performance Verification & Adjustment Procedures

Page 11 of 19

Procedure #: CP1005   Revision: A

CFG253  ADJUSTMENT PROCEDURE

NOTE:

The Adjustment procedure should be performed only by

qualified service technicians.

CONTENTS:

Preparation

11

Test equipment requirements

12

Set U1 input voltage

12

Set Q5 gate voltage

12

Adjust square wave duty cycle

13

Set DC offset

14

Square wave overshoot, rise and fall times

15

Set output levels

15

Sine wave distortion

16

Frequency dial accuracy

17

Reassembly

19

PREPARATION FOR ADJUSTMENT

This procedure should be accomplished at an ambient temperature of 21 to 25 degrees C and
a relative humidity of 75% or less.

It is necessary to remove the bottom cover from the instrument to gain access to the
adjustments used in this procedure.

Turn off the POWER switch, disconnect the power cord and place the CFG253 upside down
on its top.

Remove the 2 screws in the rear feet and the 2 screws BESIDE the front feet.

Carefully lift the bottom cover off the unit, remove the handle and set these aside along with
the screws for later reassembly.

Reconnect the power cord from an appropriate AC power source and allow the instrument a
20 minute warm up period.

Содержание CFG253

Страница 1: ...e Procedures Product CFG253 3 Mhz Function Generator Title Performance Verification Adjustment Procedure CP1005 Revision A Prepared By Roy Lindley Measurement Business Service Support REVISION LEVEL SUMMARY Revision Date Initiator Level Change From To Description A 5 16 97 Roy Lindley n a Initial release ...

Страница 2: ...Dial Accuracy 9 INTRODUCTION To ensure instrument accuracy check its performance after every 2000 hours of operation or once each year if used infrequently The instrument case does not have to be removed for the Performance Check procedure All necessary controls and connectors are accessible from the outside Test Equipment Requirement Example Test Oscilloscope 5mV 5V Div 50nS Div Tek TDS210 Freque...

Страница 3: ...N All Buttons Out VOLTS OUT Button Out FREQ 10 Button Out SWEEP Button Out SWEEP RATE Midrange SWEEP WIDTH Midrange FREQ DIAL 0 3 1 CHECK DC Offset a Pull out the DC OFFSET knob b Test Scope Set Up Volts Div 2V Time Div 0 2 mSec c Connect MAIN OUTPUT to test scope vertical input via coax cable and 50 ohm terminator d Set test scope Vert Coupling to GROUND center the trace then set Coupling back to...

Страница 4: ...nator d Check the test scope display for 5 divisions 10V e Rotate the AMPLITUDE knob to nearly CCW f Set test scope to 10 mV Div Check that the display reduces to less than 5 divisions 50mV as the AMPLITUDE knob approaches the CCW stop g Set the VOLTS OUT button in and change the test scope Volts Div to 5mV h Check for a display of 1 division 5mV as the knob approaches the CCW stop i Set the test ...

Страница 5: ... 3 2V Div 5 Div Triangle 1K Out 0 3 2V Div 5 Div m Remove the 50 ohm terminator and connect the coax cable directly to the test scope input n Set the test scope Time Div to 1uSec o Check the test scope display for each setting in Table 2 TABLE 2 Function Range Volts Out Freq Dial Volts D iv Display Triangle 1M Out 3 0 5V Div 4 Div SquareWave 1M Out 3 0 5V Div 4 Div Sine Wave 1M Out 3 0 5V Div 4 Di...

Страница 6: ...E 100K FUNCTION Square Wave VOLTS OUT Button Out FREQ 10 Button Out FREQ DIAL 3 0 c Connect MAIN OUTPUT to test scope vertical input via coax cable WITHOUT the 50 ohm terminator d Adjust AMPLITUDE knob for a 4 division display on the test scope e Set Time Div to 50 nSec Div Adjust Trig Level control as necessary to display the rising edge of the Square Wave f Check risetime between the 10 and 90 p...

Страница 7: ...e over 10 divisions e Check for nearly equal positive and negative half cycles 50 duty cycle Readjust the variable Time Div as necessary to maintain 1 complete cycle over 10 divisions f Set FREQ 10 button out g Check that the frequency increases by a factor of 10 as shown by a display of approximately 1 cycle per division on the test scope h Set the FREQ 10 button in Rotate the SYMMETRY knob CCW a...

Страница 8: ...50 Duty Cycle 100K 0 3 OUT 2 uSec 50 Duty Cycle 1M 0 3 IN 2 uSec 50 Duty Cycle 5 SYNC TTL OUTPUT a Set Up AMPLITUDE CW RANGE 1K FUNCTION Triangle VOLTS OUT Button Out FREQ 10 Button Out FREQ DIAL 3 0 b Test Scope Set Up Volts Div 1 V Time Div 0 2 mSec c Connect SYNC TTL OUTPUT directly to the test scope vertical input via a coax cable without the 50 ohm terminator d Check the test scope for a disp...

Страница 9: ...nalyzer via coax cable and 50 ohm terminator c Set the Distortion Analyzer INPUT RANGE to Auto Range and the FUNCTION settings to Volts Auto Range and THD N d CHECK For less than 1 distortion for the frequencies listed in Table 5 Table 5 RANGE FREQ DIAL PER CENT DISTORTION 100K 1 0 1 10K 1 8 1 1K 1 8 1 100 1 8 1 10 1 0 1 7 FREQUENCY DIAL ACCURACY a Set Up AMPLITUDE CW RANGE 1K FUNCTION Triangle VO...

Страница 10: ...ding for each set up listed in Table 6 Table 6 RANGE FREQ DIAL COUNTER READING 1 M 3 0 2 85 MHz 3 15 MHz 1 M 0 3 150 KHz 450 KHz 100 K 3 0 285 KHz 315 KHz 10 K 3 0 28 5KHz 31 5KHz 1 K 3 0 2 85KHz 3 15KHz 100 3 0 285 Hz 315 Hz 10 3 0 28 5 Hz 31 5 Hz 1 3 0 2 85 Hz 3 15 Hz The Frequency reading accuracy is 5 of full scale 5 of 3 MHz is 150 KHz c Disconnect cable from the Counter and CFG253 ...

Страница 11: ...mbly 19 PREPARATION FOR ADJUSTMENT This procedure should be accomplished at an ambient temperature of 21 to 25 degrees C and a relative humidity of 75 or less It is necessary to remove the bottom cover from the instrument to gain access to the adjustments used in this procedure Turn off the POWER switch disconnect the power cord and place the CFG253 upside down on its top Remove the 2 screws in th...

Страница 12: ... 1K FUNCTION All Buttons Out VOLTS OUT Button Out FREQ 10 Button Out SWEEP Button Out SWEEP RATE Midrange SWEEP WIDTH Midrange FREQ DIAL 0 3 1 Set U1 Input Voltage a Set digital multimeter to DC mV range b Connect multimeter test leads to pins 2 and 3 of Integrated Circuit U1 Note Alternate Test Points Locate R8 and R9 at the front left edge of the Main circuit board Pin 2 is connected to the end ...

Страница 13: ...Time Div control to set the display for 1 complete cycle over 10 divisions e Adjust R67 for equal positive and negative half cycles 50 duty cycle Readjust the variable Time Div as necessary to maintain 1 complete cycle over 10 divisions f Set FREQ 10 button out g Adjust R126 for 1 cycle per division on the test scope h Repeat steps d and e to set the 50 duty cycles for the settings and adjustments...

Страница 14: ... test scope Vert Coupling to GROUND center the trace then set Coupling back to DC e While turning the DC OFFSET knob from CCW to CW and back adjust R117 for equal voltage swings positive and negative on the test scope f Adjust R129 for 5 1 V with DC OFFSET knob CW and 5 1 V with the knob CCW 2 55 Div on test scope Repeat step e if necessary g Push the DC OFFSET knob in off h Set the test scope to ...

Страница 15: ...nator d Adjust AMPLITUDE knob for a 4 division display on the test scope e Adjust C31 for minimum overshoot will not be completely flat f Set Time Div to 50 nSec Div Adjust Trig Level control as necessary to display the rising edge of the Square Wave g Check risetime between the 10 and 90 points for 100 nSec 2 Div h Set test scope Trig Slope to negative Adjust Trig Level to view the Falling edge o...

Страница 16: ...bserve the display amplitude for 10 V while turning the FREQ DIAL from 0 3 to 3 0 h Set the FREQ DIAL to 3 0 Adjust C55 for the same amplitude as observed in step f i Repeat steps a thru h for the Sine Wave function In step d adjust R74 for 10 8 V In step h use C26 j Set FUNCTION to Square Wave RANGE to 1K and FREQ DIAL to 3 0 k Adjust R56 for approximately 10 8 V on the test scope display 5 4 Div...

Страница 17: ...Procedure If Distortion Analyzer is not available f Test Scope Set Up Volts Div 2V Time Div 1 uSec g Connect MAIN OUTPUT to test scope vertical input via coax cable and 50 ohm terminator h Adjust R46 for minimum distortion at top of sinewave and R43 for minimum distortion at the bottom 7 FREQUENCY DIAL ACCURACY a Set Up AMPLITUDE CW RANGE 1K FUNCTION Triangle VOLTS OUT Button In FREQ 10 Button Out...

Страница 18: ... Set Up AMPLITUDE CW RANGE 1K FUNCTION Triangle VOLTS OUT Button Out FREQ 10 Button Out FREQ DIAL 3 0 g Test Scope Set Up Volts Div 0 5 V Time Div 0 2 mSec h Connect SYNC TTL OUTPUT to test scope vertical input via coax cable and 50 ohm terminator i Adjust R6 for a display of 6 cycles in 10 Divisions on the test scope 3KHz j Set RANGE to 1M and the test scope Time Div to 0 2 uSec k Adjust C8 for a...

Страница 19: ...n off the POWER switch and remove the power cord 2 With the unit setting upside down on its top place the handle upside down in its opening in the case top and carefully slide the case bottom onto the unit Be sure that the front and back grooves line up and slip over the front and rear panels 3 Reinstall the two rear feet and screws plus the two front screws ...

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