I am assessing a client's PC (HP Pavilion) and upon plugging the power cord into the PSU, I noticed immediately that the small light next to the connector on the PSU was flashing green. As I tried to start up the PC, nothing happened. I mean nothing! My immediate reaction was to begin with troubleshooting the PSU.
My first step was to attempt to reset the PSU. I disconnected the power cord (edit: I also disconnected the 24 pin power, p4 power, and SATA power from all the drives), and switched the small red switch from 115 over to 230 and then back to 115. I then attempted to reconnect the power cord and restart but got the same result.
Next I decided to check the PSU. Utilizing a power supply tester, I verified that the 24 pin power, p4 power, and SATA power were all working properly. This leads me to believe that my PSU is functioning properly and the problem might be with the motherboard.
The motherboard exhibits no obvious physical signs of damage (capacitors are not bulging or leaking). It should be noted though that upon first opening this case, there was a substantial amount of dust inside (I mean enough to form mounds at the bottom).
I am a fairly inexperienced technician and am still learning when it comes to diagnosing problems. I believe it could very well be the motherboard but I do not want to overlook something due to my inexperience. Any input on whether or not I am missing something here? Or is my diagnosis of a faulty motherboard sound accurate? Any help is appreciated so thank you in advance!