Calibration - Main Outputs - TTI PL Series Service Manual

Equipment Required
A 5.5 digit multimeter with better than 0.05% accuracy on voltage and better than 0.1% accuracy
on current or use a precision current shunt.
A small switch, 18K resistor and a diode.
Preparation
Preset adjustments are accessible from both sides of the main pcb, their idents are also marked
on both sides of the pcb.
Take great care not to touch the mains connections on the transformers during adjustment. Use
an insulated trim tool. Allow five minutes warm-up before proceeding.
Calibration
To avoid errors when making voltage measurements the DVM must be connected directly to the
sense terminals.
Voltage - Differential Gain
Remove the link between + O/P and + sense only and fit a diode, cathode to + sense and anode
to + O/P. Connect the small switch across the diode. Connect the 18K resistor between - O/P
and + sense. Connect the DVM set to 20V range to the sense terminals.
Close the switch
Set the DC output switch on
Set the output voltage to approximately 14V
Note the reading
Open the switch and adjust VR9 for the same reading +/- 0.5mV
Close and open the switch and check the reading
Voltage - Output and meter
Remove the switch and 18K resistor and refit the link between +O/P and + sense.
Set coarse and fine controls to maximum and adjust VR3 to 32.1V or 15.6 on PL154 on the
external DVM.
Adjust VR6 so the internal meter reads the same as the DVM.
Current
Set output switch to OFF
Set the current limit control for a reading of 10mA
Set output switch to ON ON and short the output terminals
Adjust VR8 for a reading of 10mA
Remove the short and connect an ammeter between the output terminals.
Set current limit to approximately:
900mA
1800mA
2700mA
3600mA
and adjust VR7 so that the internal and external ammeters read the same.
12
Calibration – Main Outputs
- PL310
- PL320
- PL330
- PL154