SPD3303-C Power Supply is stuck in Constant Current (CC) mode

November 9, 2018

The most common reason that the SPD3303-C is stuck in constant current mode (CC.. indicated by a red LED between the channel outputs) is an incorrect voltage setting on the inputs.

Here is a picture of the voltage settings at 220 V, but with 120 V input power:

Note that with no load attached, the supply still indicates that the output is in constant current mode. This is a false indication due to the incorrect value of the MAINS input selection switches.

With the correct voltage selected (120 V, in this case), the unit is operating as expected: