Hi, Okay, without waffling, I'll try to give as much info as possible here. I was doing some hardware updates to my Mac Pro (1,1 - 2006) and so had it running with the door off and the ODD kind of sticking out. I was restarting quite a lot. One time I pressed the power button and it came on but made a popping noise, followed by a gentle burning smell :-( The fans all came on crazy fast and just kept going. The power light is solid white and no other internal LEDs can be seen. I've tried removing everything, a bit at a time. Graphics card, ram, hdds, raid card etc. but no change. I then tried testing the voltages on the molex connector for the DVD drive. 12v as expected on one side, but no 5v on the other. I therefore assumed power supply was at fault. Got a replacement. Fitted it (fiddly little thing!) and now... Same thing. I've gone back to the logic board and unplugged the ODD power lead so I can test it directly on the board and same thing. So... Does this mean I've fried part of my logic board? Popped a capacitor or something? Is there anyway I can find out? Don't really want to take it to the apple store as I get the feeling ill be wasting my time. Plus, it's really heavy to ate on the metro! I also don't want to sink too much more money in it as I've just spent loads on upgrading it and now another £70 on a power supply I may not have needed... ANY advice on how to check/if its likely the logic board/if I should replace or repair etc... Other info: Original Mac Pro (2006/07) model 1,1 Upgraded CPUs to 2x4 core 3ghz 20gb ram 4 x 3tb hdd in raid with hardware controller Running ML with chameleon boot (so old hdd on IDE connector for this) SSD for os and apps, also on IDE connector DVD drive on 'spare' ODD sata connector Ati radeon 5770 graphics card Thanks!