Heathkit Model IT-18

In-circuit / Out-of-circuit Transistor Tester

Calibration Procedure

· The meter pointer should be on the extreme left-hand mark on the meter scale as shown in 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 fresh D cell (1-1/2 volt battery) in the battery holder.  Make sure the positive (+) end of the battery is facing the positive (+) terminal of the battery holder (refer to Figure 2.)

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

· Always recalibrate the meter when a new battery has been installed.

Ancillary Equipment Needed

180-ohm 5% resistor (brown-gray-brown-gold)

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Initial Condition Adjustments

Refer to Figure 1.

(    )         Set the POLARITY switch (NPN-OFF-PNP) to the OFF position.

(    )         Set the BETA CAL. control maximum counter-clockwise.

(    )         Set the BETA multiplier switch to the X1 position.

(    )         Set the LEAKAGE control [on rear of FUNCTION switch] maximum counter-clockwise (when viewed from the rear of the panel).

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(    )         Connect a 180-ohm 5% (brown-gray-brown-gold) resistor between the collector (red) and the emitter (white) test leads.

· Do not allow the meter to go off scale to the right and remain this way for any length of time, as this could damage the meter movement.

(    )         Set the POLARITY switch to the NPN position.

(    )         Hold the FUNCTION switch (I_CEO-BETA-I_CBO) in the I_CEO position.

(    )         Adjust the LEAKAGE control (on the rear of the FUNCTION switch) until the meter indicates 5K (full scale) on the leakage scale of the meter.

(    )         Set the FUNCTION switch to the BETA position.

(    )         Set the POLARITY switch to the OFF position.

(    )         Connect the 180-ohm resistor between the base (green) and collector (red) test leads.

(    )         Set the POLARITY switch to the NPN position.

(    )         Hold the FUNCTION switch in the I_CBO position.

(    )         The meter should read full scale without readjustment of the LEAKAGE control.

(    )         Set the FUNCTION switch to the BETA position.

(    )         Set the POLARITY switch to the OFF position.

(    )         Disconnect the 180-ohm resistor from the test leads.

(    )         Calibration procedure is complete.