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 1
Ω
. 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 –OUTPUT; connect a small switch across the diode. Leave the link in
place b OUTPUT and + SENSE and connect a 15k
Ω
resistor b OUTPUT and
– 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.
