I have an Early 2008 Mac Pro (3,1). I have 18GB ram and an ATI Radeon HD 5770 1024 card installed. I have made no hardware changes in over a year. I regularly shut down the computer nightly. The symptom: I push the power button on the front and I hear a single click from the power supply. I do not get boot, do not get chime, do not get fan spin, do not get video. Just *CLICK* and then nothing. Steps I have taken so far: 1. Reset the SMC (unplugged for more than 15s, plug in, push power button) 2. Tried a different power cable (yes, I really did) 3. Tried a different outlet (yes but not a different _circuit_) 4. Removed the RAM cards and, with power plugged in, pressed the diagnostic LED button. LED #2 (Standby Trickle Pwr) comes on solid yellow. According to the service manual this tells me that the PSU is providing trickle power I can give it a kind of jump start by removing the power cable, plugging it in, and pushing the power button really quick. I'm using the computer right now, in fact. After doing the jump start trick I played Starcraft II yesterday totally maxed out at 2560x1600 for a couple hours and never had a single problem. I'm going to run Hardware Diagnostics after posting this but, in a nutshell, I'm wondering if anyone can suggest something else to try before I order a replacement PSU. It seems to me like that's the problem. Where should I get one?