Heathkit Model ig-1272 Audio Generator




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Heathkit Model IG-1272

Audio Generator

 

Date Calibrated:   _____/_____/_____


Calibration Procedure

 

         With the power supply off, the meter pointer should be over the zero reading on the meter face.  If it is not, turn the mechanical zero-adjust screw at the bottom of the meter until the pointer is properly aligned.



 

         Disconnect all external cables, components, and wires from the output terminals.


Ancillary Equipment Needed

 

AC VTVM (analog)



25 MHz Oscilloscope

50  coax cable (RG-58)

Frequency Counter

High Impedance VTVM

Distortion Analyzer (optional)
* * * * * * *

FRONT PANEL INITIAL SETUP

Refer to PICTORIAL 4-2

Illustration Booklet, page 7

 

(    )         Adjust the LEVEL control counter-clockwise to the OFF position.



 

(    )         Set the X100 MULTIPLIER pushbutton to the ON (in) position.

 

(    )         Set the 10 pushbutton of the 0–90 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.



 

(    )         Set the 10 ATTENUATOR pushbutton to the OFF (out) position.

 

(    )         Set the 20 ATTENUATOR pushbutton to the OFF (out) position.



 

(    )         Set the 40 ATTENUATOR pushbutton to the OFF (out) position.

 

(    )         Set the EXT LOAD pushbutton in the OFF (out) position.


* * * * * * *

CIRCUIT BOARD INITIAL SETUP

Refer to PICTORIAL 4-3

Illustration Booklet, page 7

 

(    )         Adjust the METER ADJ control [R132] to the center of rotation.



 

(    )         Adjust the DIST ADJ control [R109] to the center of rotation.

 

(    )         Adjust the X1000 ADJ control [R107] to the center of rotation.



 

(    )         Adjust the BIAS ADJ control [R112] to the 10 o’clock position.

 

(    )         Adjust the FREQ ADJ trimmer [C101] to the center of rotation.



               (Position the notch as shown in the PICTORIAL.)

 

* * * * * * *



CALIBRATION

 

(    )         Connect the line cord to the AC power line.



 

(    )         Adjust the LEVEL control clockwise until the click. (Pilot lamp should light.)

 

(    )         Adjust the LEVEL control to maximum clockwise.



 

(    )         Adjust the METER ADJ control [R132] counter-clockwise until the meter indicates full scale on the 10-volt scale.

 

* * * * * * *

Oscilloscope Setup

 

(    )         Set the oscilloscope’s vertical attenuator for a 40-volt input signal.



 

         If the oscilloscope will not display a 40-volt signal, use a X10 attenuator probe. DO NOT readjust the Generator’s LEVEL control.

 

(    )         Set the oscilloscope’s horizontal sweep for a 1000 Hz [1 ms] signal.



 

(    )         Connect a coax cable to the oscilloscope’s vertical input.

 

* * * * * * *

Generator Setup

 

(    )         Set the X1000 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Set the 10 pushbutton of the 0–90 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.

 

(    )         Set the EXT LOAD pushbutton in the OFF (out) position.



 

(    )         Adjust the LEVEL control to maximum clockwise.

 

(    )         Connect the same coax cable to the 10V OUT output jack of the generator.



 

(    )         Adjust the DIST ADJ control [R109] until the oscilloscope’s trace is just clipping on both peaks of the waveform.

 

(    )         Adjust the BIAS ADJ control [R112] for symmetrical clipping of the trace.



 

(    )         Adjust the DIST ADJ control [R109] until the clipping just disappears.

 

(    )         Adjust the LEVEL control to the maximum counter-clockwise OFF position.



 

(    )         Disconnect the oscilloscope from the generator.


* * * * * * *

AC VTVM setup

Refer to PICTORIAL 4-3 & 4-5

Illustration Booklet, pages 7 & 8

 

(    )         Set the AC VTVM on the 10-volt scale.



 

(    )         Connect a coax cable, or a set of test leads, to the AC VTVM’s input jacks.

 

(    )         Connect the same coax cable, or set of test leads, to the 10V OUT output jack of the generator.



 

(    )         Set the X100 MULTIPLIER pushbutton to the ON (in) position.

 

(    )         Set the 10 pushbutton of the 0–90 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.



 

(    )         Adjust the LEVEL control to maximum clockwise.

 

(    )         Adjust the DIST ADJ control [R109] for a 10-volt AC VTVM reading.



 

(    )         Adjust the METER ADJ control [R132] for a 10-volt front panel indication.

 

(    )         Set the X1000 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Adjust the X1000 ADJ control [R107] until the front panel meter indicates full scale on the 10-volt scale.

 

(    )         Disconnect the AC VTVM from the generator.



 

* * * * * * *

Oscilloscope setup

 

(    )         Connect the oscilloscope the same as above.



 

(    )         Set the 90 pushbutton of the 0–90 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.

 

(    )         Adjust the LEVEL control to maximum clockwise.



 

(    )         Observe the oscilloscope’s trace for clipping.

 

(    )         Adjust the BIAS control [R112] for either no clipping or symmetrical clipping.



 

(    )         Adjust the LEVEL control to the maximum counter-clockwise OFF position.

 

(    )         Disconnect the oscilloscope from the generator.


* * * * * * *

HIGH FREQUENCY CALIBRATION
Frequency Counter setup

 

(    )         Connect a coax cable to the frequency counter.



 

(    )         Connect the same coax cable to the 10V OUT output jack of the generator.

 

(    )         Set the X1000 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–90 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.

 

(    )         Adjust the LEVEL control to maximum clockwise.



 

(    )         Adjust the FREQ ADJ trimmer [C101] for a Frequency Counter reading of 90 kHz +/- 2 kHz.


* * * * * * *

FUNCTIONAL CHECKS

 

Variable Frequency Control Check

 

(    )         Set the 0 pushbutton of the 0–90 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.



 

(    )         Set the X1 MULTIPLIER pushbutton to the ON (in) position.

 

(    )         Perform the three marked steps X1 below.



 

(    )         The readings should be approximately 9 Hz to approximately 110 Hz.

 

  X1     X10      X100    X1000



(    )  (    )   (    )   (    )1   Adjust the VARIABLE FREQUENCY control [R3/R4] to maximum counter-clockwise.

 

(    )  (    )   (    )   (    )2   Adjust the VARIABLE FREQUENCY control slowly to maximum clockwise.



                                   

(    )  (    )   (    )   (    )3   Adjust the LEVEL control to maximum counter-clockwise OFF position.

 

(    )         Set the X10 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Repeat the three marked steps X10 above.

 

(    )         The readings should be approximately 90 Hz to approximately 1100 Hz.



 

(    )         Set the X100 MULTIPLIER pushbutton to the ON (in) position.

 

(    )         Repeat the three marked steps X100 above.



 

(    )         The readings should be approximately 900 Hz to approximately 11 kHz.

 

(    )         Set the X1000 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Repeat the three marked steps X1000 above.

 

(    )         The readings should be approximately 9 kHz to approximately 110 kHz.



 

(    )         Disconnect the frequency counter from the generator.

 

Selector Switch Check

 

(    )         Set the X1000 MULTIPLIER pushbutton to the ON (in) position.



 

(    )         Repeat the two marked steps 1 below for each pushbutton (0 –> 90) of the 0–90 selector switch bank.          

 

   0       10       20       30         40       50       60       70         80       90            Set the X pushbutton of the 0–90 selector switch bank to the



(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )1          ON (in) position.

                                                                                   

   0       10       20       30         40       50       60       70         80       90            Observe the meter reading at each switch position, indication

(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )1     should stay the same.

 

(    )         Repeat the two marked steps 2 below for each pushbutton (0 –> 9) of the 0–9 selector switch bank.



 

   0        1        2        3          4        5        6        7        8        9               Set the X pushbutton of the 0–9 selector switch bank to the

(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )2     ON (in) position.

 

   0        1        2        3          4        5        6        7        8        9               Observe the meter reading at each switch position, indication 



(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )2     should stay the same.

 

(    )         Repeat the two marked steps 3 below for each pushbutton (0 –> .9) of the 0–0.9 selector switch bank.          



 

   0        .1       .2       .3         .4       .5       .6       .7       .8       .9               Set the X pushbutton of the 0–0.9 selector switch bank to the

(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )3     ON (in) position.

 

   0        .1       .2       .3         .4       .5       .6       .7       .8       .9               Observe the meter reading at each switch position, indication



(    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )  (    )3     should stay the same.

 

(    )         Adjust the LEVEL control to the maximum counter-clockwise OFF position.



 

Attenuator Switches and External Load Switch Check

 

         The accuracy of these measurements will be +/- .2 dB +/- the accuracy of the AC VTVM.



 

(    )         Set the AC VTVM to measure from 10 to 70 dB.

 

(    )         Connect the AC VTVM to the 10V OUT output jack of the generator.



 

(    )         Set the X100 MULTIPLIER pushbutton to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–90 selector switch bank to the ON (in) position.



 

(    )         Set the 0 pushbutton of the 0–9 selector switch bank to the ON (in) position.

 

(    )         Set the 0 pushbutton of the 0–0.9 selector switch bank to the ON (in) position.



 

(    )         Set all three ATTENUATOR pushbuttons to the OFF (out) position.

 

(    )         Record the AC VTVM reading.   __________



 

(    )         Set the X10 ATTENUATOR pushbutton to the ON (in) position.

               (The reading should be 10 dB below original meter indication)

 

(    )         Set the X10 ATTENUATOR pushbutton to the OFF (out) position.



 

(    )         Set the X20 ATTENUATOR pushbutton to the ON (in) position.

               (The reading should be 20 dB below original meter indication)

 

(    )         Set both the X10 and X20 ATTENUATOR pushbuttons to the ON (in) position.



               (The reading should be 30 dB below original meter indication)

 

(    )         Set both the X10 and X20 ATTENUATOR pushbuttons to the OFF (out) position.



 

(    )         Set the X40 ATTENUATOR pushbutton to the ON (in) position.

               (The reading should be 40 dB below original meter reading)

 

(    )         Set both the X10 and X40 ATTENUATOR pushbuttons to the ON (in) position.



               (The reading should be 50 dB below original meter indication)

 

(    )         Set the X10 ATTENUATOR pushbutton to the OFF (out) position.



 

(    )         Set both the X20 and X40 ATTENUATOR pushbuttons to the ON (in) position.

               (The reading should be 60 dB below original meter indication)

 

(    )         Set all the X10, X20, and X40 ATTENUATOR pushbuttons to the ON (in) position.



               (The reading should be 70 dB below original meter indication)

 

(    )         Set the AC VTVM on the 10-volt scale.



 

(    )         Set all three ATTENUATOR pushbuttons to the OFF (out) position.

 

(    )         Set the EXT LOAD pushbutton to the ON (in) position.



               (The AC VTVM reading should increase slightly.)

 

(    )         Set the EXT LOAD pushbutton to the OFF (out) position.



               (The original AC VTVM indication should return.)

 

(    )         Disconnect the AC VTVM.



 

(    )         Connect a high impedance (12 k or higher) voltmeter [VTVM] to the SYNC output [rear of unit].

 

(    )         The meter reading should be at least 1 volt rms.



 

♦ After the unit has been operated for at least 48 hours, readjust both the DIST ADJ [R109] and the METER ADJ [R132] controls for a 10-volt output.

 

(    )         Disconnect all test leads and cables from the unit.



 

(    )         Set the POWER switch to the OFF position.

 

(    )         Disconnect the line cord from the AC power lines.



 

(    )         Calibration procedure is complete.



 

 

 


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