This guide explores 10 common power supply problems and solutions to help you troubleshoot and resolve issues such as failure to power up, voltage inconsistencies, and overheating. This reference design detects milliampere-level AC and DC ground fault currents for residual current detection (RCD) and ground fault current interrupters (GFCI), targeted to meet timing and accuracy requirements for UL2331-2 and IEC62752. The 24 V line is actually about 10. I have tested ZD1 and ZD2 which seem to be fine. Over time, dust, dirt, and debris can accumulate inside the power supply unit, which may obstruct airflow and cause elevated temperatures. Are you sufficiently competent to work around high voltages? If you feel it's within your abilities, start by tracing the circuit and making a schematic.