Voltage Calibration
Connect DMM, set to Volts, across output. Set voltage controls to minimum and current control to maximum. Switch output ON and check for a reading of 00·00V ± 0·01V on display and DMM.
Set voltage controls to maximum. Adjust VR16/VR116 (maximum output volts) for a reading of 35·30V ± 0·02V on the DMM. Adjust VR2/VR102 (preset volts) until display matches DMM.
Connect rheostat to output and adjust for nominally 4A at maximum output voltage. Reduce current limit (current control anticlockwise) until output just enters CI mode. Adjust VR8/VR108 (measured volts) until display matches DMM reading.
Current Calibration
Connect DMM, set to 20A range, in series with rheostat set to about 1Ω. With output OFF set voltage controls to maximum and current control to 0·10A. Switch output ON and adjust VR1/VR101 for 0·10A ± ·01A on DMM.
Set voltage controls to 12V, current control to maximum; supply should be in CI mode. Adjust VR6/VR106 (maximum output current) for 10·20A ± ·02A on DMM.
Switch output OFF. Adjust VR3/VR103 (preset current) until display matches maximum output set by VR6/VR106 above.
Increase rheostat resistance until unit enters CV mode. Adjust VR1/VR101 (measured current) on Main board until display matches DMM reading.
Set Power Limit
Switch output OFF, set voltage control to 12·1V, current control to maximum. Switch output ON, set rheostat so that current is 10·0A (ensure CV mode is maintained). Adjust VR5/VR105 (power limit) until the UNREG l.e.d. just lights; back off VR5/VR105 until CV is lit and UNREG is off.
Set voltage controls to maximum and check unit enters UNREG mode. Increase rheostat resistance until unit enters CV mode again; check meter reads between 5A and 6·2A.
Remove load.
OVP Calibration
Set voltage controls to minimum, current control to maximum. Set VR7/VR107 fully anti- clockwise. Switch output ON. Press OVP button and set front panel OVP control (screwdriver adjustment) for a display of 20·00V; release OVP button.
Set output voltage to 20·00V and adjust VR7/VR107 (OVP calibrate) slowly anticlockwise until OVP is tripped (display reads TRIP). Turn output OFF and reset front panel OVP control fully clockwise.
Voltage Regulation
Remove the link between the – OUTPUT and – SENSE terminals and fit a diode, anode to
–SENSE and cathode to
–SENSE. Connect the DMM, set to Volts, between the sense terminals.
Close the switch, switch the output ON and set the output to 18·xxxx on the DMM; note the exact reading. Open the switch and adjust VR4/VR104 for exactly the same reading; close the switch again and check the reading is unchanged.
Remove the diode, resistor and switch and refit the sense link.
