Heathkit Model IP-20

Transistorized Power Supply

Calibration Procedure

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

Ancillary Equipment Needed

10 ohm 25 watts resistor (optional)

Differential Voltmeter (optional)

* * * * * * *

NOTES

· Remove all jumper wires between the circuit grounds and chassis ground.

· Remove all loads from the supply terminals.

· Always change the VOLTAGE RANGE switch slowly to avoid possible voltage transients that may damage the transistors.

* * * * * * *

Front Panel Initial Conditions

(    )         Set the POWER switch [on back of unit] to the OFF position.

(    )         Set the VOLTAGE RANGE switch to the AC OFF position.

(    )         Set the CURRENT RANGE switch to the 1.5A position.

(    )         Set the FINE VOLTAGE control to center of rotation.

(    )         Set the CURRENT LIMIT control maximum clockwise.

(    )         Set the METER switch to the VOLTAGE position.

(    )         Remove the guard nut from the DC REGULATOR control.

(    )         Set the DC REGULATION control to 1/8 turns from full counter-clockwise.

(    )         Replace the guard nut on the DC REGULATOR control.

(    )         Set the D.C. ON – RESET STANDBY switch to the RESET STANDBY position.

*Control Plate* Initial Conditions

(    )         Set the *ZENER CURRENT* control maximum count-clockwise.

(    )         Set the *VOLTAGE CALIBRATE* control to center of rotation.

(    )         Set the *METER* switch to the ZENER CURRENT position.

(    )         Set the POWER switch [on back of unit] to the ON position. Allow the tubes to come up to operating temperature.

(    )         Set the VOLTAGE RANGE switch to the 5V position.

(    )         Adjust the *VOLTAGE CALIBRATE* control for a 5 ma (full scale) meter reading.

(    )         Set the *METER* switch to the NORMAL position.

(    )         Set the D.C. ON – RESET STANDBY switch to the D.C. ON position.

· The 10 & 15 volt ranges use the 0 - 15 scale. The remaining ranges use the 0 - 50 scale.

(    )*       Adjust the FINE VOLTAGE control and observe the meter move from almost zero to full scale.

(    )*       Set the FINE VOLTAGE control maximum counter-clockwise.

· Repeat the above two steps* while slowly incrementing the VOLTAGE RANGE switch from the 5V to the 50V positions.

(    )         Set the VOLTAGE RANGE switch to the 50V position.

(    )         Set the FINE VOLTAGE control maximum clockwise.

(    )*       Adjust the *VOLTAGE CALIBRATE* control for a full scale meter reading.

(    )*       Set the *METER* switch to the ZENER CURRENT position.

(    )*       Adjust the *ZENER CURRENT* control for a full scale meter reading.

(    )*       Set the *METER* switch to the NORMAL position.

· Because the *VOLTAGE CONTROL* and the *ZENER CURRENT* control interact with each other, it will be necessary to repeat the above four steps* until no meter changes are observed.

(    )         Set the *METER* switch to the NORMAL position.

(    )         Decrement the VOLTAGE RANGE switch from the 50V to the AC OFF positions.

DC REGULATION CONTROL ADJUSTMENT

(optional)

· If a differential voltmeter is not available, leave the DC REGULATION control as originally set and proceed to the FINAL ADJUSTMENTS section.

Front Panel Initial Conditions

(    )         Increment the VOLTAGE RANGE switch to the 15V position.

(    )         Set the METER switch to the VOLTAGE position.

(    )         Set the CURRENT RANGE switch to the 1.5A position.

(    )         Set the CURRENT LIMIT control maximum clockwise.

(    )         Remove the guard nut from the DC REGULATOR control.

(    )         Set the D.C. ON – RESET STANDBY switch to the RESET STANDBY position.

(    )         Connect a differential voltmeter across the output terminals.

(    )         Set the D.C. ON – RESET STANDBY switch to the D.C. ON position.

(    )*       Measure the unloaded output voltage using the differential voltmeter.

(    )*       Set the D.C. ON – RESET STANDBY switch to the RESET STANDBY position.

(    )*       Connect a 10 ohm 25 watts resistor to the output terminals.

(    )*       Set the D.C. ON – RESET STANDBY switch to the D.C. ON position.

(    )*       Measure the loaded output voltage using the differential voltmeter.

(    )*       Adjust the *DC REGULATION* control to match the unloaded meter readings.

(    )*       Set the D.C. ON – RESET STANDBY switch to the RESET STANDBY position.

(    )*       Disconnect the 10 ohm resistor from the output terminals.

· In order for the output voltage regulation to be the same both loaded and non-loaded, it will be necessary to repeat the above eight steps* until no meter changes are observed.

(    )         Disconnect the differential voltmeter from the output.

FINAL ADJUSTMENTS

(    )         Replace the guard nut on the DC REGULATOR control.

(    )         Set the D.C. ON – RESET STANDBY switch to the RESET STANDBY position.

(    )         Set the FINE VOLTAGE control maximum counter-clockwise.

(    )         Decrement the VOLTAGE RANGE switch slowly from 15V to AC OFF.

(    )         Set the POWER switch [on back of unit] to the OFF position.

(    )         Calibration procedure is complete.