Heathkit Model IG-1277

Pulse Generator

Calibration Procedure

· Disconnect all external components from the front panel terminals.

Ancillary Equipment Needed

35 MHz Oscilloscope

50 W cable (RG-58)

50 W Termination Adapter

VTVM

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FRONT PANEL INITIAL SETUP

Refer to PICTORIAL 4-1

Illustration Booklet, page 4

(    )         Set the PERIOD switch [SW101] to the 10 msec position.

(    )         Set the DELAY switch [SW102] to the 10 msec position.

(    )         Set the WIDTH switch [SW103] to the 1 msec position.

(    )         Adjust the PERIOD control [R2] to maximum counter-clockwise.

(    )         Adjust the DELAY control [R3] to maximum counter-clockwise.

(    )         Adjust the WIDTH control [R4] to maximum counter-clockwise.

(    )         Adjust the TRIG LEVEL control [R1] to center of rotation.

(    )         Adjust the OFFSET control [R7] to center of rotation.

(    )         Adjust the 50W AMPLITUDE control [R5] to center of rotation.

(    )         Set the POWER switch to the OFF (out) position.

(    )         Set the RUN GATE switch to the ON (in) position.

(    )         Set the TRIG DELAY switch to the ON (in) position.

(    )         Set all the remaining pushbutton switches to the OFF (out) position.

CIRCUIT BOARD INITIAL SETUP

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Refer to PICTORIAL 4-2

Illustration Booklet, page 4

(    )         Adjust the PERIOD CAL control [R116] to center of rotation [circuit board – right front].

(    )         Adjust the WIDTH CAL control [R126] to center of rotation [circuit board – left front].

(    )         Adjust the DELAY CAL control [R121] to center of rotation [circuit board – center front].

(    )         Adjust the OFFSET CAL control [R151] to center of rotation [circuit board – center rear].

(    )         Adjust the Trimmer control [C129] to 9 o’clock position (solder dot) [circuit board – left front].

INITIAL TESTS

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Refer to Detail 4-2B

Construction Manual, page 40

(    )         Set the VTVM FUNCTION switch to the OHMS position.

(    )         Set the VTVM RANGE switch to the X1000 position.

(    )         Connect the VTVM’s common lead to the heat sink [circuit board].

(    )         Connect the VTVM’s probe to one of the line cord’s flat prongs.

(    )         VTVM meter indication should be infinite.

(    )         Disconnect the VTVM’s probe.

(    )         Connect the VTVM’s probe to the other line cord flat prong.

(    )         VTVM meter indication should be infinite.

(    )         Disconnect the VTVM’s common lead.

(    )         Connect the VTVM’s common lead to the line cord’s free flat prong.

(    )         Set the POWER switch to the ON (in) position.

(    )         VTVM meter indication should be near zero.

(    )         Disconnect both the VTVM’s probe and common lead.

(    )         Set the POWER switch to the OFF (out) position.

(    )         Connect the VTVM’s common lead to the heat sink [circuit board].

(    )         Set the VTVM RANGE switch to the X10 position.

(    )         Connect the VTVM’s probe to the collector [mounting tab] of transistor Q107.

(    )         VTVM meter indication should exceed 25 W.

(    )         Disconnect the VTVM’s probe.

(    )         Connect the VTVM’s probe to the collector [mounting tab] of transistor Q108.

(    )         VTVM meter indication should exceed 25 W.

(    )         Disconnect the VTVM’s probe.

(    )         Connect the VTVM’s probe to the collector [heat sink] of transistor Q106.

(    )         VTVM meter indication should exceed 1000 W.

(    )         Disconnect both the VTVM’s probe and common lead.

CALIBRATION

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Refer to PICTORIAL 4-4

Illustration Booklet, page 15

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Oscilloscope Setup

(    )         Set the oscilloscope’s VERTICLE INPUT to the GND position.

(    )         Set the oscilloscope’s VERTICLE INPUT ATTENUATOR to the 0.1 volts/div position.

(    )         Set the oscilloscope’s HORIZONTAL SWEEP RATE to the 1 msec/div position.

(    )         Adjust the oscilloscope’s trace to the center of the display.

(    )         Set the oscilloscope’s VERTICAL INPUT to the DC position.

(    )         Connect a 50 W termination adapter to the oscilloscope’s vertical input.

(    )         Connect an RG-58 coax cable to the termination adapter.

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(    )         Connect the generator’s line cord to the AC line voltage.

(    )         Verify front panel settings are as described in the Front Panel Initial Setup section above.

(    )         Connect the same coax cable to the generator’s 50 W OUT jack.

(    )         Set the EXT TRIG switch to the ON (in) position.

(    )         Set the POWER switch to the ON (in) position.

(    )         Adjust the OFFSET CAL control [R151 – circuit board] to center the oscilloscope’s trace.

(    )         Switch the oscilloscope’s input between DC and GND several times to verify the trace appears at exactly the same vertical position.

(    )         Set the RUN GATE switch to the ON (in) position.

(    )         Set the PERIOD switch to the 1 msec position.

(    )         Set the oscilloscope’s VERTICAL ATTENUATOR to the 1 volts/div position.

(    )         Adjust the oscilloscope’s SWEEP TRIGGER for a trace.

(    )         Set the oscilloscope’s HORIZONTAL SWEEP RATE for at least one full visible pulse trace.

(    )         Adjust the 50 W AMPLITUDE control to produce a peek-to-peek trace of 5 volts (5 divisions).

(    )         Adjust the trimmer capacitor [C129 – circuit board] to produce a slight overshoot on the waveform trace, see Figure A-A [Illustration Booklet, page 15].

· The leading edge of the pulse should appear as straight and vertical as possible.

· Adjustments to both the PERIOD and WIDTH controls may be required.

(    )         Set the PERIOD switch to the 10 msec position.

(    )         Adjust the PERIOD control to maximum counter-clockwise.

(    )         Set the oscilloscope’s HORIZONTAL SWEEP RATE to 2 msec/div.

(    )         Adjust the PERIOD CAL control [R116 – circuit board] for a pulse period trace of exactly 5 divisions, see Figure A-B [Illustration Booklet, page 15].

(    )         Set the WIDTH switch to the 10 msec position.

(    )         Adjust the WIDTH control to maximum counter-clockwise.

(    )         Adjust the PERIOD control a quarter-turn clockwise to insure no overlap condition occurs.

(    )         Adjust the WIDTH CAL control [R126 – circuit board] for a pulse width trace of 5 divisions, see Figure A-C [Illustration Booklet, page 15].

(    )         Disconnect the coax cable from the 50 W termination adapter.

(    )         Disconnect the 50 W termination adapter from the oscilloscope’s input.

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

(    )         Disconnect the coax cable from the 50 W OUT jack.

(    )         Connect the coax cable to the TRIG OUT jack.

(    )         Adjust the DELAY control to maximum counter-clockwise.

(    )         Adjust the oscilloscope’s vertical attenuator as necessary.

(    )         Adjust the DELAY CAL control [R121 – circuit board] for a trace of 5 divisions wide.

(    )         Disconnect the coax cable from the generator.

(    )         Disconnect the coax cable from the oscilloscope.

(    )         Set the POWER switch to the OFF position.

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

(    )         Calibration procedure is complete.