The following procedure should be undertaken:
- Check the functionality of the Power Switch. Verify that it has continuity in the ON position, and equipped a disconnect (is open circuit) in the OFF position. Check all poles of the switch.
- If the Inverter is capable of operating at multiple input Voltages, confirm about the working of any external voltage selection switches.
- When the Inverter is first powered up the Bus capacitors (Main filter capacitors) are pre-charged for several seconds. This is to restrict the inrush current, as a capacitor appears as a short circuit to the incoming power supply (Main input supply) at time equal to zero. If this is not done, the Input Rectifier and Main Power Switch would have to supply infinite current during this time (an impossible situation that finally results into component failure). A high wattage resistor restricts this initial current. Verify that this resistor is closed circuit, or degraded.
- Optically examine the Bus Capacitors. These are generally large Radial electrolytic Capacitors. Make sure that the cases are not distorted and that they are not leaking the electrolyte. Ensure that the Bus Capacitors are fully discharged. Measure the value of capacitors using a Capacitance meter.
- With a DVM(Digital Volt Meter), kept in the Diode position, verify that the Mains Input Rectifier and Secondary output diodes are working. The diodes should display a forward voltage drop of between 0.2 to 0.8 V DC when the Anode is positive in respect to the cathode. An open circuit condition, (displayed as OL on some DVM’s) will be shown when the probes are everted.