Heathkit model IG-1271
Function Generator
Date Calibrated: _____/_____/_____
• The Accuracy of the calibration of the IG-1271 Function Generator is dependent upon the accuracy of the Oscilloscope used.
There are two methods described here for calibrating the Function Generator.
o Method #1 requires the use of a triggered oscilloscope and a frequency counter.
o Method #2 requires the use of a triggered oscilloscope or an audio distortion analyzer.
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Handle and Cover Removal
( ) Disconnect all external cables, components, and wires from all the equipment input and output terminals.
( ) Disconnect the Function Generator line cord from the AC power line.
( ) Remove the two Thumb screws and hardware along with the handle from the sides of the cabinet.
( ) Remove the four screws from the rear and bottom of the cabinet.
( ) Slide the top cover off the chassis.
♦ CAUTION: Dangerous AC voltage is present around the line cord leads on the circuit board and on the back of switch (SW-3).
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Calibration Procedure method #1
Ancillary Equipment Needed
Frequency Counter
Triggered Oscilloscope
Audio Distortion Analyzer
* * * * * * *
FRONT PANEL INITIAL ADJUSTMENTS
Refer to Figure 2-1 on page 39
( ) Set the ATTENUATION (dB) switch (SW-3) [black knob] to the 10 position.
( ) Set the FREQUENCY MULTIPLIER switch (SW-1) [black knob] to the 1k position.
( ) Set the FUNCTION switch (SW-2) [red knob] to the sawtooth wave position.
CIRCUIT BOARD INITIAL ADJUSTMENTS
Refer to Figure 1-2
Fold-out page 33
( ) Set the HIGH FREQ DIAL ADJ (R4) to the center of rotation.
( ) Set the LOW FREQ DIAL ADJ (R2) control to the center of rotation.
( ) Set the SYM ADJ control (R7) to the center of rotation.
BNC CABLE CONNECTIONS
Refer to Figure 1-1
Fold-out page 33
( ) Connect a BNC tee-connector to the vertical input of the Oscilloscope.
( ) Connect a BNC tee-connector to the input of the Frequency Counter.
( ) Connect a BNC cable between the output of the Function Generator and the vertical input of the Oscilloscope.
( ) Connect a BNC cable between the vertical input of the Oscilloscope and the input of the Frequency Counter.
( ) Connection to the Audio Distortion Analyzer is not made at this time.
( ) Connect the Function Generator, Oscilloscope, and the Frequency Counter line cords to the AC power line.
( ) Adjust the VARIABLE control (R33 & SW5) [red knob] clockwise until control clicks to the ON position.
( ) Set the Frequency Generator and the Oscilloscope to their ON positions and allow the instruments to warm up.
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OSCILLOSCOPE INITIAL SETUP
( ) Set the vertical input attenuator switch to the 5 V/DIV position.
( ) Set the Trigger source switch to INT.
( ) Set the Trigger type switch to AC.
( ) Set the Trigger polarity switch to + (positive).
( ) Set the Trigger mode switch to AUTO.
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FUNCTION GENERATOR ADJUSTMENTS
Refer figure 2-1 on page 39
*( ) ( ) ( )1 Set the oscilloscope TIME/CM switch to the 1 mSEC/DIV position.
*( ) ( ) ( )2 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 0.1.
*( ) ( ) ( ) Adjust the VARIABLE control (R33) [red knob] clockwise for a 20 volts peak-to-peak trace on the oscilloscope (see figure 3 on page 33).
*( ) ( ) ( )3 Adjust the oscilloscope sweep rate until one complete sawtooth trace is displayed (see figure 3 on page 33).
NOTE: It may be necessary to adjust the LOW FREQ DIAL ADJ control (R2) [circuit board] to obtain this trace.
*( ) ( ) ( )4 Adjust the LOW FREQ DIAL ADJ control (R2) [circuit board] until the negative going ramp covers five divisions (see figure 4 on page 33).
*( ) ( ) ( ) Set the oscilloscope Trigger polarity switch to -- (negative).
*( ) ( ) ( )5 Adjust the SYM ADJ control (R7) [circuit board] until the positive going ramp covers five divisions (see figure 5 on page 33).
*( ) ( ) ( )6 Adjust the DC OFFSET ADJ control (R32) [circuit board] until the trace is equally positioned above and below the zero reference line on the Oscilloscope (see figure 5 on page 33).
*( ) ( ) ( ) Set the oscilloscope TRIGGER polarity to + (positive).
*( ) ( ) ( )7 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 10.
*( ) ( ) ( )8 Adjust the HIGH FREQ DIAL ADJ control (R4) [circuit board] until the Frequency Counter reads 10 kHz.
*( ) ( ) ( )9 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 1.
*( ) ( ) ( )10 Adjust the LOW FREQ DIAL ADJ control (R2) [circuit board] until the Frequency Counter reads 1000 Hz.
NOTE: The adjustments of the LOW FREQ DIAL ADJ control (R2) and the SYM ADJ control (R7) [circuit board] interact and have a direct relation to the amount of distortion output by the Function Generator.
( )11 Repeat the above thirteen marked (*) steps twice more.
( )12 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 10.
( )13 Set the FREQUENCY MULTIPLIER switch (SW1) [black knob] to the 10k position.
( )14 Adjust the 10k ADJ trimmer (C4) [circuit board] until the Frequency Counter reads 100 kHz.
( )15 Set the FREQUENCY MULTIPLIER switch (SW1) [black knob] to the 100k position.
( )16 Adjust the 100k ADJ trimmer (C3) [circuit board] until the Frequency Counter reads 1 MHz.
( ) Disconnect all external cables from the output terminals.
( ) Calibration procedure [method #1] is complete.
( ) Proceed to the Distortion Adjustments section below.
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Calibration Procedure method #2
Ancillary Equipment Needed
Audio distortion analyzer
Triggered Oscilloscope
* * * * * * *
FRONT PANEL INITIAL ADJUSTMENTS
Refer to Figure 2-1 on page 39
( ) Set the ATTENUATION (dB) switch (SW-3) [black knob] to the 10 position.
( ) Set the FREQUENCY MULTIPLIER switch (SW-1) [black knob] to the 1k position.
( ) Set the FUNCTION switch (SW-2) [red knob] to the sawtooth wave position.
CIRCUIT BOARD INITIAL ADJUSTMENTS
Refer to Figure 1-2
Fold-out page 33
( ) Set the HIGH FREQ DIAL ADJ control (R4) to the center of rotation.
( ) Set the LOW FREQ DIAL ADJ control (R2) to the center of rotation.
( ) Set the SYM ADJ control (R7) to the center of rotation.
BNC CABLE CONNECTIONS
Refer to Figure 1-3 on page 34
( ) Connect a BNC cable between the output of the Function Generator and the vertical input of the Oscilloscope.
( ) Connect the Function Generator, Oscilloscope, and Audio Distortion Analyzer line cords to the AC power line.
( ) Adjust the VARIABLE control (R33 & SW5) [red knob] clockwise until control clicks to the ON position.
( ) Set the Oscilloscope and the Audio Distortion Analyzer to their ON positions and allow the instruments to warm up.
* * * * * * *
OSCILLOSCOPE INITIAL SETUP
( ) Set the vertical input attenuator switch to the 5 V/DIV position.
( ) Set the Trigger source switch to INT.
( ) Set the Trigger type switch to AC.
( ) Set the Trigger polarity switch to + (positive).
( ) Set the Trigger mode switch to AUTO.
* * * * * * *
FUNCTION GENERATOR ADJUSTMENTS
Refer figure 2-1 on page 39
*( ) ( ) ( )1 Set the oscilloscope TIME/CM switch to the 1 mSEC/DIV position.
*( ) ( ) ( )2 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 0.1.
*( ) ( ) ( ) Adjust the VARIABLE control (R33) [red knob] clockwise for a 20 volts peak-to-peak trace on the oscilloscope (see figure 3 on page 35).
*( ) ( ) ( )3 Adjust the oscilloscope sweep rate until one complete sawtooth trace is displayed (see figure 3 on page 35).
NOTE: It may be necessary to adjust the LOW FREQ DIAL ADJ control (R2) [circuit board] to obtain this trace.
*( ) ( ) ( )4 Adjust the LOW FREQ DIAL ADJ control (R2) [circuit board] until the negative going ramp covers five divisions (see figure 4 on page 35).
*( ) ( ) ( ) Set the oscilloscope Trigger polarity switch to -- (negative).
*( ) ( ) ( )5 Adjust the SYM ADJ control (R7) [circuit board] until the positive going ramp covers five divisions (see figure 5 on page 35).
*( ) ( ) ( ) Set the oscilloscope Trigger polarity switch to + (positive).
*( ) ( ) ( )6 Adjust the FREQUENCY (Hz) control (R301) [black knob] to the 10 indication.
*( ) ( ) ( )7 Set the oscilloscope TIME/CM switch to the 10 mSEC/DIV position.
*( ) ( ) ( )8 Adjust the HIGH FREQ DIAL ADJ control (R4) [circuit board] until the positive going ramp plus the negative going ramp covers ten oscilloscope divisions.
( )9 Repeat the above eleven marked (*) steps twice more.
( )10 Adjust the FREQUENCY (Hz) control (R301) [black knob] to 10.
( )11 Set the FREQUENCY MULTIPLIER switch (SW-1) [black knob] to the 10k position.
( )12 Set the oscilloscope TIME/CM switch to the 2 mSEC/DIV position.
( )13 Adjust the 10k ADJ trimmer (C4) [circuit board] until the positive going ramp plus the negative going ramp covers five oscilloscope divisions (see figure 13 on page 35).
( )14 Set the FREQUENCY MULTIPLIER switch (SW1) [black knob] to the 100k position.
( )15 Set the oscilloscope TIME/CM switch to the .5 mSEC/DIV position.
( )16 Adjust the 100k ADJ trimmer (C4) [circuit board] until five cycles are displayed spanning ten divisions on the oscilloscope (see figure 16 on page 35).
( ) Calibration procedure [method #2] is complete.
( ) Proceed to the Distortion Adjustments section below.
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Distortion Adjustments
Ancillary Equipment Needed
Audio Distortion analyzer
Triggered Oscilloscope
Notch Filter (see page 32)
There are two methods described here for adjusting for distortion:
o Method #1 requires the use of a Triggered oscilloscope.
o Method #2 requires the use of an audio distortion analyzer.
* * * * * * *
FRONT PANEL INITIAL ADJUSTMENTS
Refer to Figure 2-1 on page 39
( ) Adjust the FREQUENCY (Hz) control (R301) [black knob] to the full counter clockwise position.
( ) Set the FREQUENCY MULTIPLIER switch (SW-1) [black knob] to the 1k position.
( ) Set the FUNCTION switch (SW-2) [red knob] to the sawtooth wave position.
( ) Set the ATTENUATION (dB) switch (SW-3) [black knob] to the 0 position.
( ) Adjust the VARIABLE control (R33) [red knob] to the full clockwise position.
( ) Set the function generator and the oscilloscope or the audio distortion analyzer to their ON positions and allowed to warm up.
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Distortion Compensation method #1
Ancillary Equipment Needed
Triggered Oscilloscope
Notch Filter (see page 32)
* * * * * * *
OSCILLOSCOPE INITIAL SETUP
( ) Set the TIME/CM switch to the 1 mSEC/DIV position.
( ) Set the vertical input attenuator switch to the 5 V/DIV position.
( ) Set the Trigger source switch to INT.
( ) Set the Trigger type switch to AC.
( ) Set the Trigger polarity switch to + (positive).
( ) Set the Trigger mode switch to AUTO.
( ) Connect the output of the Function Generator to the vertical input of the Oscilloscope (figure 1-3 on page 34).
( ) Adjust the VARIABLE control (R33) [red knob] clockwise for a 20 volts peak-to-peak trace on the oscilloscope.
( ) Disconnect the vertical input of the Oscilloscope.
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NOTCH FILTER CONNECTIONS
Refer to figure 1-4
Fold out page 34
( ) Connect the output of the Function Generator to the input of the Notch Filter [loop end].
( ) Connect the Oscilloscope’s vertical input to the Notch Filter’s output [straight end].
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CIRCUIT BOARD ADJUSTMENTS
Refer to Figure 1-2
Fold out page 33
*( ) ( ) ( ) Adjust the FREQUENCY (Hz) control (R301) [black knob] until a minimum output indication is obtained.
*( ) ( ) ( ) Adjust the + DIST control (R23) [circuit board] until a minimum output indication is obtained.
*( ) ( ) ( ) Adjust the -- DIST control (R26) [circuit board] until a minimum output indication is obtained.
( ) Repeat the above three marked (*) steps twice more.
( ) Distortion compensation [method #1] is complete.
( ) Disconnect all external cables from all terminals.
( ) Set the VARIABLE control (R33 & SW5) [red knob] counter-clockwise to the OFF position.
( ) All calibrations and adjustments are now completed.
( ) Disconnect the line cord from the AC power lines.
( ) Re-install cover and handle.
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Distortion Compensation method #2
Ancillary Equipment Needed
Audio Distortion Analyzer
Notch Filter (see page 32)
* * * * * * *
AUDIO DISTORTION ANALYZER INITIAL SETUP
( ) Set the Audio Distortion Analyzer attenuator switch to the 20 volts scale*.
( ) Connect the output of the Function Generator to the input of the Audio Distortion Analyzer (figure 1-3 on page 34).
( ) Adjust the VARIABLE control (R33) [red knob] clockwise for a 20 volts* meter indication.
NOTE: * Use which ever Audio Distortion Analyzer attenuation setting that produces a full scale indication at the maximum generator output.
( ) Disconnect the input to the Audio Distortion Analyzer.
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NOTCH FILTER CONNECTIONS
Refer to figure 1-4
Fold out page 34
( ) Connect the output of the Function Generator to the input of the Notch Filter [loop end].
( ) Connect the Audio Distortion Analyzer’s input to the Notch Filter’s output [straight end].
* * * * * * *
CIRCUIT BOARD ADJUSTMENTS
Refer to Figure 1-2
Fold out page 33
*( ) ( ) ( ) Adjust the FREQUENCY (Hz) control (R301) [black knob] until a minimum output indication is obtained.
NOTE: Use which ever attenuation setting that produces a full scale indication at this minimum generator output.
*( ) ( ) ( ) Adjust the + DIST control (R23) [circuit board] until a minimum output indication is obtained.
*( ) ( ) ( ) Adjust the -- DIST control (R26) [circuit board] until a minimum output indication is obtained.
( ) Repeat the above three marked (*) steps twice more.
( ) Distortion compensation [method #2] is complete.
( ) Disconnect all external cables from all terminals.
( ) Set the VARIABLE control (R33 & SW5) [red knob] counter-clockwise to the OFF position.
( ) All calibrations and adjustments are now completed.
( ) Disconnect the line cord from the AC power lines.
( ) Re-install cover and handle.