XPS 420, blinking amber power light, one on yellow light on mobo and a blinking green on the ethernet port.
Initially replaced the power supply as it seemed like the common cause. Nothing changed, so I assumed it was the motherboard. Put it in a new motherboard today, same problem. Now I'm just racking my brain trying to figure this out and for the life of me, I can't determine the problem.
Cancel that, That IDE cable for the front USB port is also the power switch. So that's needed. Not sure if that's what triggered the two fans to turn on and CD-Rom and Hard Drive to turn on. Not sure what to troubleshoot next.
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here: http://www.cwc-group.com/casp.html
You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.
Motherboard LED's mean very little. When on, all they are telling you is that the computer os plugged into a live power socket and the PSU is switched.
Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.
If no beeps:
At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.
The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card. Silence or long single beeps indicate a problem with the memory.
Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
So.... this was unexpected. A short in two of the three front USB ports on the front portion of the case. Dell uses an odd connector that is meant for the USB ports and the power switch.
I brought the computer in to find a short in the system and we found them in the USB ports.
It's a new idea to me. But it's booting now.
A machine with the same boot problem (power button flashing yellow, but nothing else) was brought to me yesterday. Initially, I thought the power supply had died. Power supply was ok (tested), and even replaced with a different one just in case. Same issue.
I then unplugged the IDE/USB connector from the motherboard (the one running from underneath the power supply all the way to the front of the PC). I plugged the power cord in, and the machine booted.
Turns out, there was some damage done to the front USB ports (like something inserted that shouldn't have been, thereby bending the pins to the point where they were touching each other and other parts of the interior of that module).
I unbent the pins, plugged the IDE/USB connector back to where it was before and the machine was fine. Probably won't be able to use the front USB jacks, but the PC is back in commission.
Same issue here. No amber light for me though. Absolutely nothing would happen when I pressed the power button. I looked at the front USB port adjacent to the headphone jack and it is all kinds of messed up. Looks like the user tried to put a PS/2 plug in it. I unplugged the IDE-like cable and the unit turned on immediately. I will attempt to unbend the pins and move on. Thanks for the excellent follow-thru on the post. I usually don't find my answer on the first forum click, this was the exception.