Can a blown power supply = fried motherboard?

[jonnyboyrich]

Yesterday, as I was working on my computer, it died. Just as though someone had unplugged it. I knew I had a short, so I tried a new power supply cable. When I got the new one in, I hit the power button and the power supply unit popped and started smoking. I now know the short was in the unit itself. So I picked up a new power supply unit and installed it. The problem now is that I have power to my computer, but nothing works. For example. The power supply unit fan runs and the processor fan runs. The light for the CD Drives comes on for a quick flash then goes off. The green light that usually indicated the computer is on flashes on and off once. But I cannot get my CD drives to open and I cannot get a display on my monitor. What are the chances that when the power supply blew, it took my motherboard (or at least parts of my motherboard) with it, and how can I tell before I buy a knew motherboard?

[Thong_Ispector]

It concerns me that you had a short but didnt do anything about it...

How did you know there was a short?

After it died....
You replaced just the power cord to the PSU and it blew smoke after that?

Seems odd...

Is the "new" PSU you installed after the problem started a used one from another source, or NEW...?

Does the CPU fan run all the time or does it only work when you hit the power button. Does the CPU fan plug onto the motherboard or directly to the power supply...

Is this an ATX board with the front of case power switch going to the motherboardor an earlier board where the power switch on the front of the case has 110/220 vac going to it?

Also the fact that the cd drive doors will not open...

If you unplug the data/bus cable and only leave the power cable connected to them will the drawer/door open?

[dcc]

Ouch...that one could cost you. Next time use either a VOM or DMM to check the out put of the PSU, and a continuity test on the power cord (unpluged). Most PSUs have DC voltages ranging from +3.3v to +20v, and -5v to -20v. If there was a short in the secondary of the psu you could have sent higher voltages to devices that don't respond well to that kind of treatment, and yes it could have killed your CPU and other chips. There is a multipin connector that goes to the motherboard from the SPU, which provides a number of dedicated circuits that go to user specific sites, so it is possibe to have some devices opperate while others will not. There are other dedicated circuits coming out of the SPU that go to such devices as the CD, fans,etc, and a voltage spike could have effected them as well. All of this is dependent on the voltage handling capacity of the diferent devices, and how wide spread the spike was. I have a friend who decided to play electician and put up a new dinning room light, what he didn't realize was that there were two different 110v potentials from two different bus bars producing 220v in this box, when he turned on the lights, they burned very bright, and very breifly. This is prety much what would have happened on a component level in your case. I wish you luck.

[djrivera1]

Yesterday, as I was working on my computer, it died. Just as though someone had unplugged it. I knew I had a short, so I tried a new power supply cable. When I got the new one in, I hit the power button and the power supply unit popped and started smoking. I now know the short was in the unit itself. So I picked up a new power supply unit and installed it. The problem now is that I have power to my computer, but nothing works. For example. The power supply unit fan runs and the processor fan runs. The light for the CD Drives comes on for a quick flash then goes off. The green light that usually indicated the computer is on flashes on and off once. But I cannot get my CD drives to open and I cannot get a display on my monitor. What are the chances that when the power supply blew, it took my motherboard (or at least parts of my motherboard) with it, and how can I tell before I buy a knew motherboard?

Your drives is more likely still good. Replaced Motheboard, computer will more likely work again, The same thing happen to me one before on my older p4 system, drives turn on won't open and nothing on the screen fans still worked. I replaced the motherboard, computer is good as new.

[BullHorn]

A while ago I had the same thing.

PSU died, slowly killed my MoBo.

[marvelous1]

hey , i put together a nice pc about a month ago geforce 7950 gt oc asus mobo 2 gigs of corsair ram xtreme gamer fatality sound card and a 500 watt psu from raidmax that came with my case . i usually leave my pc on and i occasionally turn it off or restart it. but one night i left it on and i went upstairs to go play a game and it wouldnt turn on. i switched power cords and all that and i took the psu out and called raidmax they gave me a test and it failed. it wasnt puttin power out. what could have caused this and could there be any damage to other parts of my pc?

[pc newb]

build cheap pc ....case came with 380w ps....started pc after build...installed os....no problems thru several restarts.... set all bios appropriately...restarted pc and checked emails...shut down....on restart no power...replugged everything on board and reinstalled ram to make sure no probs there....took to frys for ps test..(bad ps) ...replaced ps and all is good...now next morning ...nothing on monitor though all seems to be working in case

[JANINE1]

build cheap pc ....case came with 380w ps....started pc after build...installed os....no problems thru several restarts.... set all bios appropriately...restarted pc and checked emails...shut down....on restart no power...replugged everything on board and reinstalled ram to make sure no probs there....took to frys for ps test..(bad ps) ...replaced ps and all is good...now next morning ...nothing on monitor though all seems to be working in case

have you checked that your graphics adapter card is properly seated? sometimes its quite easy to knock these things just slightly out of position.

failing that there is a possibiliy that when your pc went down it took out the graphics adaptor card or its slot which would mean replacement parts

[rubberman]

Normally, a blown power supply does == fried motherboard. Once voltage drops below certain specs, current goes up to compensate, and that generally fries stuff. Whether or not your hard drives got fried also is questionable. Pull them out, place in some sort of drive dock or enclosure, and try to access them from another computer. If you can access them, then you need to replace the power supply and motherboard. If they don't, then you need an entirely new system, and I hope you have backups!

[rubberman]

A bad power supply can easily fry a motherboard, and other components (disc drives, add-in boards, etc). How? The computation for power is A (power) = V (volts) x I (amps of current). The power requirements of a component is linear or dependent upon load. If the voltage drops because of a bad power supply, the current increases in order to keep the power stable or deliver the power the components require. At some point, the current (producing heat) is too great, and "snap, crackle, pop" goes your system... :-(

[KevinMcK]

It's P=EI (Joule's law), and it *is* true that *for the same power* the current would have to be higher if the voltage were lower. However, will the power be the same?

There is another law called "Ohm's Law" which states I=E/R (where I is current, E is electromotive force aka "voltage" and R is resistance or impedance). From these it holds that P=E^2/R (P is power). This means that the current and power supplied to the load will both go *down* if the voltage goes down.

A failing power supply will *not* "keep the power stable or deliver the power the components require" so this theory doesn't hold. Not to say that a faulty power supply can't blow a connected load - it *can*, but this would be as a result of a (possibly momentary) voltage *increase* (possibly due to faulty regulation).

A typical failure mode for switching power supplies is for the catch diode to blow. The output inductor is drained into the load through the catch diode in the return path, so if it blows, the load can no longer utilize the energy stored in the inductor, and power, voltage, and current delivered to the load all go down.

Most times I've had a power supply fail, all components worked fine with a new power supply. Not always, but usually.