Heathkit model CM-1073

Automotive Tune-up Meter

 

Date Calibrated:   _____/_____/_____

 

Calibration Procedure

•         With the meter off, the meter pointer should be over the 0 volts indication on the meter face.  If it is not, adjust the mechanical zero-adjust screw at the bottom of the meter until it does.

 

•         Calibration cable – a light duty extension cord with no outlet on the end of it; with a 10K 5% ½ watt resistor (brown-black-orange-gold) soldered to the end of one of the wires. If using a polarized plug extension cord, the resistor should be attached to the hot side of the line (smaller blade of the two).

 

•         CAUTION:    DO NOT plug the calibration cable into the 120 VAC 60 Hz line without it being properly     connected to the meter test leads first!

 

•         Use a screwdriver with an insulated handle when making the circuit board adjustments. DO NOT come into contact with the metal shaft.

 

Ancillary Equipment Needed

 

Automotive battery(s)

Calibration cable

 

* * * * * * *

INITIAL TEST

Refer to Figure 1

(Fold-out from page 13)

(    )         Set the FUNCTION switch to the DC VOLTS position.

 

(    )         The CYLINDERS switch may be in any position.

 

(    )         Connect the black test lead to the negative (--) post of a battery of not over 15-volts.

 

(    )         Touch the red test lead to the positive (+) battery post.

 

(    )         Meter should indicate the voltage of the battery.

 

(    )*       If the meter tries to indicate down scale, reverse test leads to the battery.

 

(    )         Disconnect the test leads from the battery.

 

* * * * * * *

ZERO SET

 

(    )         Position the instrument so that the meter is facing upward.

 

(    )         Connect (short) the two test leads together.

 

(    )         Adjust the meter Zero Set screw so that the meter pointer reads exactly zero.

 

(    )         Disconnect the two test leads from each other.

 

* * * * * * *

DWELL Calibration

Refer to Figure 2

 

Note:       If possible, this calibration should be performed using a standard fully charged 6-volt automotive battery. After calibration, the instrument should be checked using a fully charged 12-volt automotive battery. The meter readings should be approximately the same for both automotive voltages. If a 6-volt battery is unavailable (older automotive electrical systems), a standard 12-volt battery will work just fine.

 

(    )         Set the FUNCTION switch to the DWELL position.

 

(    )         Set the CYLINDERS switch to any position.

 

(    )         Observing correct polarity, connect the black test clip to the negative (-) terminal and the red test clip to the positive (+) terminal of any DC voltage source between 5 and 15 volts, such as an automotive battery.

 

(    )         Adjust the DWELL CAL control [located near the top of the circuit board] until the meter reads full scale.

 

(    )         Disconnect the test clips from the voltage source.

 

* * * * * * *

TACHOMETER CALIBRATION

Refer to Figure 3.

 

•         Use extreme care when using AC line voltage.  Personal shock or meter damage can result from carelessness.

 

(    )         Set the FUNCTION switch to the LOW RPM position.

 

(    )         Set the CYLINDERS switch to the 6 position.

 

(    )         Set the TAC CAL control [located near the bottom of the circuit board] to midrange.

 

(    )         Connect the meter’s test clips to the calibration cable: [red alligator clip to the resistor lead - the resistor needs to be in series with the meter], and the [black alligator clip to the plain lead].

 

•         The calibration cable should not remain plugged into the AC line any longer than necessary to accomplish the calibration (about 2 – 3 minutes).  The resistor will overheat if left on for too long a time.

 

•         CAUTION:    Use a screwdriver with an insulated handle.

 

(    )         Plug the calibration cable into a 120 VAC 60 Hz outlet.

 

(    )         Adjust the TAC CAL control until the meter reads 1200 RPMs (12 on the 0 – 15 scale).

 

(    )         Set the CYLINDERS switch to the 8 position.

 

(    )         The meter should read 900 RPMs (9 on the 0 – 15 scale).

 

(    )         Set the FUNCTION switch to the HIGH RPM position.

 

(    )         Set the CYLINDERS switch to the 4 position.

 

(    )         The meter should read 1800 RPMs (18 on the 0 – 45 scale).

 

(    )         Set the CYLINDERS switch to the 3 position.

 

(    )         The meter should read 2400 RPMs (24 on the 0 – 45 scale).

 

•         CAUTION:    Always unplug the calibration cable from the AC line first!

 

(    )         Disconnect the test cable from the 120 VAC 60 Hz outlet.

 

(    )         Disconnect the test leads from the calibration cable.

 

(    )         Calibration procedure is complete.