Gateway MX3414 - Dead CPU?

Greetings friends.

I am servicing a Gateway MX3414. The client brought it to me and explained that when you pushed the power button, the LED's flashed for a moment, the CD indicator would flash three times, and nothing else would happen.

After he mentioned that it frequently got hot and that he had someone else "blow out the fans once", I explained that the most likely candidate was the GPU on the motherboard. I hooked it to a known good (and powered on) monitor, booted, tried alt+f4 several times (and at several different points of time after booting), and got no video.

However, the CD-Rom continued to work, and would spin up and sound like it was reading a disc when one was inserted. The fans would also kick if the machine was left to sit for while, and run at varying speeds as if they were actually adjusting to temperatures.

I pulled the battery and A/C, held the power button for a good minute. No joy. Pulled the memory and used a known good module from another computer. No joy. Held the power button again with everything pulled and the new memory module, just for poops and grins. No joy.

Oh, and I took a very bright light and shone it all around the screen, again, at various times to be sure I wasn't missing anything. No...joy.

With all this behind me, I was fairly confident in ordering a new motherboard. It arrived today. I installed it, checking and double-checking that everything was re-assembled correctly. Sexy new thermal paste on everything after a good cleaning. All screws accounted for. Clean re-assembly.

Power it on...exact same symptoms. Lights, DVD, fans...no video.

I am at a loss. The only thing I can think of is to replace the CPU, which isn't a big deal since I have several Turion64 chips lying around from dead HP's. I just don't want to take the time to rip it apart again if somebody else has any suggestions as to what I could be missing.

Any bright ideas?

pull the HDD and ODD and try POSTing without them. A short in a bad HDDs or ODD can keep a computer from POSTing properly or POSTing at all.

Another small thing I've missed before is to put memory in only one slot, but it wasn't "slot 1" to let the computer POST. aka test your known good memory in each slot. (unless you have matching good sticks, of course)

Good Luck!