No Power To Pc

Hello there,
I built a machine some years ago all was good until yesterday. Wouldn't power on, no fans, no lights or beeps. The psu had a strange odour like it was burned out. No smoke though. I got a new PSU and fitted it with a new cable, still nothing, no fans, even in the PSU. SWapped electical power points, removed and replaced all M/B wires.
Can a fried motherboard prevent power getting to the PSU?
Thanks in advance for any suggestions. old dog

 

No, but it can prevent a PSU from turning on.

Check the simple things first. Most new power supplies have a master power switch on back. Make sure it is set to the "On" (typically "1") position. This puts it in standby mode. Double check you have attached all the necessary cables. Note that most motherboards need 2, sometimes 3 separate cables directly from the power supply. And many graphics cards require 1 or 2 cables directly from the power supply.

You need to verify your new PSU is functioning properly. While not conclusive by any means, you can at least see if your PSU can power on using The Paperclip Method. Note this does NOT test to ensure all the necessary voltages are present or within tolerance. It does not test the PSU under a variety of loads. And it does not test for excessive ripple and other anomalies that affect computer stability. This is done by a qualified technician using an oscilloscope or power supply analyzer - sophisticated (and expensive) electronic test equipment requiring special training to operate, and a basic knowledge of electronics theory to understand the results. Therefore, conclusively testing a power supply is done in properly equipped electronics repair facilities.

Alternatively, a decent PSU Tester will short the two necessary pins for you and tell you if the necessary voltages are present. This model with a LCD voltage readout will tell you if the voltages are within the necessary ±5% tolerance. But these testers do not test the supply under a variety of loads, nor for ripple either. But they are good for a quick test and I keep one in my tool bag for house calls.

If your PSU powers on with the paperclip or PSU tester, you might then test the case's power switch. With the power supply fully connected to the motherboard (and master power switch set to "On", follow the two wires from the switch to the motherboard. There you will see they go to two pins on the motherboard's "front panel I/O header". You can pull the two wires and with a steady hand, momentarily short those two pins on the header together with a metal object - I use a small screwdriver. You won't hurt anything if you touch the wrong pins - just make sure you don't touch the motherboard with the screwdriver.

Shorting those two pins for a second will (if all working properly) signal the PSU to come out of standby mode and fully start.

Be sure to touch bare metal of the case interior before reaching in, and frequently after to discharge any static in your body.

If the computer starts, that tells you the case's power switch has failed. What many people do is simply flip the case's Reset button wires over to those two motherboard pins, then use the Reset button as the Power switch from then on.

Do you mean wall outlets? And are you sure there is power to those outlets? This is an obvious question but your old supply may have blown the fuse or flipped a breaker when it blew, and both outlets could be on the same circuit. I recommend every home and every computer user should have access to a AC Outlet Tester to ensure your outlet is properly wired and grounded. I recommend one with a GFCI (ground fault circuit interrupt) indicator as it can be used to test bathroom and kitchen outlets too. These testers can be found for your type and voltage outlet, foreign or domestic, at most home improvement stores, or even the electrical department at Wal-Mart. Use it to test all the outlets in the house and if a fault is shown, have it fixed by a qualified electrician.

While it is not common for a power supply to take out connected components when the supply fails, it is not unheard of either. Let's hope it didn't.

 

Thanks for the reply Digerati.
I checked the new PSU with the paperclip method and the fan comes on. I checked the old PSU and the fan didn't come on. I could very easily be wrong but I'm thinking maybe the PSU blew and caused a problem elsewhere (CPU or M/board) or a problem elsewhere blew the PSU. I have decided to upgrade the build. it's about time, I'll keep the old components and thoroughly check them out to find out what went wrong, maybe I can help someone else in the future.
Thanks to your reply, I will know what to check.

 

That link above for the paper clip method also has a link to a cmos/cmos battery check. It can be a possibility to check while your in there.

 

A failed CMOS battery will not stop a computer from starting, however. I will still start and might soon error out, but it will attempt to start. This one didn't and paper click test showed it was the PSU.

It is not likely something else took out the PSU (except an extreme power surge from the grid). But a failed PSU surely could have zapped your board or CPU or RAM.

If you normally heard a single beep before (indicating the presence of a system speaker) you typically will hear beeps if the CPU or RAM failed. You may not if the motherboard failed.

I just hope your new PSU is a quality PSU with sufficient power for your new components. Good luck.

 

This is linked from that page

If you have just replaced the power supply in your computer and it is not booting, you may want to clear the CMOS. By clearing the CMOS you will remove any settings that might have been particular to your previous power supply.

 

The link says, if the fan on the unit starts to spin then your problem may vary well be with something else like the CMOS. The OP said even the fan does not spin. It does not hurt to reset the BIOS, but I don't see that as the problem here.

 

I did normally hear a beep on starting up but not when the trouble started.From what I've read in the replies and what I've managed to find on google, it looks like it I was unlucky and the Psu took out the m/board. The new PSU is a known brand and plenty powerful enough(550W) to operate the new M/b and cpu.
Thanks for your interest

 

Well, sorry your "event" turned out to be so catastrophic. But as you noted, this system was getting along in years so this happening is a good excuse to build a new system. Good luck and seriously consider an SSD.