I have the XPS420 which mysteriously stopped working, only power was steady amber light on mobo and ethernet flashing. after a lot of fault finding it was narrowed down to the Graphic Card and also slot 3 and 4 memory. The only way i could get it to switch on was to follow these instructions found after google search.
I completely disassembled the front of the computer and disconnected the usb hub from the front. I will also note here that I had just recently yanked one of the usb connections real hard breaking it. Ok so once i had the power button that plugs into the usb hub disconnected I untied the wires. Two or three mini zip ties and then a piece of tape and unwound the six wires. There are six wires and 7 slots in the plug so one of them is not used. The end that has one wire then a space is the one you want. Take that wire and the one on the other side of the space, cut them and splice them together. Now just plug it back in, reassemble and when you plug it in it should start
I had some more problems after this. It just randomly shut off and when I powered down the power supply and turned it back on it would shut off two seconds later. So I took out the mobo battery and put it back in. Restart and it work.
After doing this i tried the graphic card and it screamed at me, so purchased a new one. This works a dream, but the only prob now is I cannot have a cmos battery in as it will not boot (have tried new ones) and also the only way i can switch it on is by unplugging at main wall switch, leaving for a minute then plugging back in, it then auto boots up without having to use power switch on front. If i try the power switch light 1 and 4 flash and it turns off. Other than that it runs like clockwork. Any ideas please?
Thanks in advance