I have an Acer AM5100-U5301A Desktop. It is mostly the standard PC I bought a few years back. I have replaced the power supply a while back and replaced a hard drive that went bad. It was working fine... now it is not.
It would not do anything when... no Power Supply fan or anything. I shorted the power supply on the 24 pin connector and it ran. Hooked it back to the motherboard and nothing. I bypassed the on switch on the computer panel and got the motherboard fans and all working. Still no hard drive or screen. The odd thing is it would work once. I would turn it off at the power supply switch behind the PC. And it would not come back on. I could separate the wires where I bypassed the front switch and reconnect them and it would work for one time... then it would not until I did this again. Sometimes the fans would start up for a second and then stop... and I would undo these wires and put them back and then the fans would run fine until I turned it off again. This is probably just something unique to bypassing the power switch. So back to the main problem.
I could not get any beeps and the hard drive would not boot... no screen display. I took out the only PCI card which was a modem and removed the memory thinking I would get the motherboard to at least respond with a beep to let me know the memory was missing. Nothing.
I am expecting the motherboard is shot, but before I gave up I thought I would post. I would love to know other troubleshooting steps and any info on cost to replace. I may just take the drive and put it in an external enclosure and put it on my router for access by the rest of the PCs since we don't use this one that much anyway, but if I can get it fixed cheap, I would give it a whirl.