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Tektronix CFG253, Service Procedures

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CFG253

Performance Verification & Adjustment Procedures

Page 3 of 19

Procedure #: CP1005   Revision: A

PREPARATION

Connect the instrument and test equipment to an appropriate power source and allow 20

minutes for warm up and stabilization.  Set the controls as listed below during warm up.

Initial CFG253 Set-Up:

AMPLITUDE

Mid Range

DC OFFSET

Pushed In

SYMMETRY

Midrange Detent

RANGE

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.

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 DC.

e.

While turning the DC OFFSET knob from CCW to CW and back, check for for >
+5 V with DC OFFSET knob CW and > -5 V with the knob CCW (+/- 2.5 Div on
test scope).

f.

Push the DC OFFSET knob in (off).

Summary of Contents for CFG253

Page 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 ...

Page 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...

Page 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...

Page 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 ...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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 ...

Page 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...

Page 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 ...

Page 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...

Page 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 ...

Page 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...

Page 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...

Page 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...

Page 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...

Page 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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