Heathkit Model IT-3120

FET / Transistor Tester

Calibration Procedure

· The meter pointer should be on the infinity mark on the meter scale (refer to Figure 1).  If the pointer is not over this mark, adjust the zero-adjust screw at the bottom of the meter until the pointer is properly aligned.

· Install a pair of fresh D cells (1-1/2 volt battery) in the battery holders.  Make sure the positive (+) end of each battery is facing the positive (+) terminal of the battery holder (refer to Pictorial 14).

· Make sure that any exposed metal parts of the test leads are not touching each other.

· Always recalibrate the meter when new batteries have been installed.

Ancillary Equipment Needed

166 W 1% resistor

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BATTERY TEST

Refer to Figure 1.

(    )         All push-button switches should initially be in the off _(out) positions.

(    )         Set the MODE - OFF / ON switch to the OFF _(out) position.

(    )         Set the RANGE switch to the 10 mA _(in) position.

(    )         Set the FUNCTION switch to the BETA = infinity _(out) position.

(    )         Set the MODE switch to the BAT. TEST _(in) position.

(    )         Set the MODE - NPN / PNP switch to the NPN _(out) position.

(    )         Set the MODE - OFF / ON switch to the ON _(in) position.

(    )         Meter indication should be within the BAT OK location on the leakage scale.

(    )         Set the MODE - NPN / PNP switch to the PNP _(in) position.

(    )         Meter indication should be within the BAT OK location on the leakage scale.

(    )         Set the MODE - OFF / ON switch to the OFF _(out) position.

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TRANSISTOR MODE ADJUSTMENTS

(    )         Connect a 166 W 1% resistor between the COLLECTOR (black) and the EMITTER (red) terminals.

(    )         Set the MODE switch to the TRANS. _(in) position.

(    )         Set the FUNCTION switch to the I_{ceo (out)} position.

(    )         Set the RANGE switch to the 10 mA _(in) position.

(    )         Set the MODE - OFF / ON switch to the ON _(in) position.

(    )*       Set the MODE - NPN / PNP switch to the PNP _(in) position.

(    )*       Set the meter calibration control [on the circuit board] until the meter indicates 85 on the leakage scale.

(    )*       Set the MODE - NPN / PNP switch to the NPN _(out) position.

(    )         If the meter indication is greater than 90 or less than 80, replace both batteries.

(    )         Repeat the three marked steps* above if the batteries were replaced.

(    )         Set the MODE - OFF / ON switch to the OFF _(out) position.

(    )         Disconnect the resistor between the COLLECTOR and the EMITTER terminals.

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FET MODE ADJUSTMENTS

(    )         Set the MODE switch to the FET _(in) position.

(    )         Set the FUNCTION switch to the G_m=0 _(in) position.

(    )         Set the RANGE switch to the 100 ma _(in) position.

(    )         Set the MODE - OFF / ON switch to the ON _(in) position.

(    )         Set the MODE – P CHAN. / N CHAN. switch to the P CHAN _(in) position.

(    )         Adjust the G_m=0 control maximum counter-clockwise to maximum clockwise.

               The meter should follow the control setting and read from below zero to over the 100 indication on the leakage scale.

(    )         Set the MODE – P CHAN. / N CHAN. switch to the N CHAN _(out) position.

(    )         Adjust the G_m=0 control from maximum counter-clockwise to maximum clockwise.

               The meter should follow the control setting and read from below zero to over the 100 indication on the leakage scale.

(    )         Set the MODE - OFF / ON switch to the OFF _(out) position.

(    )         Set all push-button switches to the off _(out) positions.

(    )         Calibration procedure is complete.