In this episode Shahriar investigates the failure of a GW Instek 1080W power supply capable of providing up to 80V and 40A of programmable output voltage and current respectively. The power supply does not power on. However, relay noises can be heard inside the instrument during power on.
Teardown of the unit reveals a modular design with PCBs on all sides. The instrument comprises 6 different modules and 3 complete power supplies in parallel. The controller circuit is powered from the middle power supply module. Examination of the boards reveals three separate failed devices. The in-rush power resistor which prevents the main supply board from startup, a damaged MOS power transistor on the supply output and surface mount resistors. All components are replaced. The instrument’s performance is verified with a BK Precision 8601 electronic load.