Computer/Power supply Electrical Question?

[TopCatGr58]

Hey Folks,

I'm not electrical engineer, so I've got a question.

Background story: Fellow workmate's son moved to an older house while attending college. I had worked on his computer before. He said he had it plugged in and hit the ON switch, heard a POP and the magic smoke came out the back!

Brought it to me. Checked it out, bad POWER SUPPLY, put another used one from one of the many older units I had, booted and ran just fine! Gave it back to him.

Said he got it home, plugged it in, and hit switch, and POW, bigger popping sound, magic smoke release again!

Brought it back to me. Took apart, heard something rattling, pulled power supply out, took cover off, and there was a CAPACITOR that had gotten BLOWN off the circuit board! There were also several others that were FRIED!!!

Put in another spare Powersupply, but this time, it didn't come on, NO POWER lights, NO post sounds, no beeps, NOTHING!

It is an older P4/2.4Ghz/533 MhzFSB on an MSI MS-7005 Mobo. I tried another Power Supply, and it also did NOTHING!

1st question is probably obvious answer....with a failing/blowing power supply, could it send a damaging surge thru the 20pin connector to the MOBO and FRY something on it to kill it?? OR...would it more likely kill the CPU?

I have told the coworker that her son/they will need to have the wiring of the old house checked out. Don't know if they might have the outlet wired wrong, possibly 220?

2nd question, could having the outlet wired backwards, common and hot backwards....cause the powersupply to get damaged?? I know it's AC current, but they have those fancy different sized plug ends to keep the polarity correct, but would it really cause a PS to immediately fry???

I have pulled the Hard Drive and video card, and have tested them on another system, and they seem to be working, but I don't have a MOBO that can handle the P4 to test it on. WE do have some P4 systems at work. I don't know what the FSB ratings are, but IF they are slower than the 533 that the CPU requires, will it work like Ram and just run slower....so that I can TRY TO TEST the cpu on the other system, or will it damage the MOBO or CPU trying to run it on a system mobo that ie. only runs 400 Mhz??

Thanks in advance!?
T.C.

[madmax-im]

TC My brother who know 'puters says the Mobo is fried...and good luck trying to find it...he says the processor might also be fried...or the voltage to the processor...if the processor smells burnt then you have your answer...my brother says he has seen this happen many a time BTW answer to #2 is yes it could fry out right away...but my brother feels its on the Mobo somewhere...Also he says you have to have a 3 prong plug with the ground for a proper connection

[madmax-im]

Re: Computer/Power supply Electrical Question?

I have pulled the Hard Drive and video card, and have tested them on another system, and they seem to be working, but I don't have a MOBO that can handle the P4 to test it on. WE do have some P4 systems at work. I don't know what the FSB ratings are, but IF they are slower than the 533 that the CPU requires, will it work like Ram and just run slower....so that I can TRY TO TEST the cpu on the other system, or will it damage the MOBO or CPU trying to run it on a system mobo that ie. only runs 400 Mhz??

Thanks in advance!?
T.C. [/B][/QUOTE]
One more thing...yes the CPU will run slower...it will only run at the speed that the Mobo is set to...some Mobos' have jumpers to adjust the speed...

[xswilly]

hey tc
i work part time at a puter repair store

we see this kind of thing all the time
usually it just frys the MB, but once in awhile it will take out the cpu also
high voltage is just as bad as low
i would suggest a battery backup, that at least will smooth out the power going in to the puter


computers run on smoke, if you let any out they stop working

[Ivan]

Similar situation occurred with a compy I worked on, found out some genius wired a 110v outlet on a 220v single phase circuit. Had 110v on the two prongs, and 220 between them. It got pretty much everything. Surprised it didn't catch something on fire.

Reminds me of the old comedy with Val Kilmer, "Top Secret" when the old german general said "It took our surgeons three hours to remove the smile from his face"

[Crazcnuk]

Most P4 mainboards will attempt to 'autosense' the new CPU and set up accordingly.

If the mainboard won't do 533, the cpu will likely still work (if it's not fried) just slower than it's used to.

Neither should fry anything.

[mro]

Hardware store should have a inexspensive tester for the outlet.
It's just a plug with a couple LED's that light up to let you know how it's wired. A DIY'er now and then will wire the common or hot to the ground. (not good )


mro

[randy]

wired a 110v outlet on a 220v single phase circuit. Had 110v on the two prongs, and 220 between them.

That is not possible. The two prongs would have to be wired to two seperate phases in order to have any potential between them.

[egsols]

I don't know what the FSB ratings are, but IF they are slower than the 533 that the CPU requires, will it work like Ram and just run slower

Haven't worked on any p4's but on the older ones I seem to remember setting the jumpers for both the cpu fsb as well as the voltage...I'm thinking that was maybe a P1 though so I don't know if they still have cpu voltage jumpers.

[boyat68]

TC:

All the PC power supplies that I have seen or owned were either 110/220 switched by a slide switch or auto sensed voltage.

It should not make a difference if you hooked the power supply into 110 or 220 except that it is against the electrical code to use a 110v wall socket to distribute 220 as the code calls for the plugs to be different. That aside, the PC power supply is designed so that you can hook it into 110 or 220 through the supplied cord and if you forget to switch the slide switch it makes no difference except the power supply will not work if you hook 220 without the slide switch. The only thing the slide switch does is shorts the two phases together at the rectifier junction

I strongly suspect that something else is wrong with your friends house wiring as the power supply left your hands intact and destroyed itself at your friends house.

[Jerry]

I strongly suspect that something else is wrong with your friends house wiring ...

Most likely the culprit for blowing the power supply is a "noisy" line; i.e. rapid frequency changes. Can happen if there is a hair dryer/blower on the same circuit, or a window AC, or anything that creates electronic noise on the line. Reminds me of my early days driving a cage, listening to the AM radio and running under a power line.....

Better UPS / line conditioners filter each outlet on the box, cheaper ones filter the incomming line. Have seen a couple cases where users plugged in small fans into the same strip as the PC and blew out the PC. Also one coffee pot / 1-cup heater, very strange.

If worst comes to worst let me know as I have access to a couple old and slow P4 motherboards (Compaq Evo) and I could send you one.

[Rhumba]

Take the CPU to the nearest comp repair shop and ask them to test it for you.

If it passes and all else is ok then the MOBO is fried.

Don't forget to test the memory too. Bad memory can stop a computer from starting up.

[TopCatGr58]

Good test results!

Well, I borrowed one of the older PC's from work today, surprisingly, it's a Compaq EVO D510c, and it recognized the CPU, gave a warning about needing to update the bios to best utilize the CPU, but I just hit F1, and it completed, booted, Windows loaded, My Computer Properties showed the test CPU was a P4-2.4Ghz, the old one in the EVO was a 1.7Ghz.

I then had a spare slave 'puter that uses standard DDR ram, so I threw the 512Mb chip in there, fired right up, showed the full amount, etc., so the Ram chip is good also.

So...looks like the Mobo is what got toasted with the PWS!

Hey Jerry, I truly appreciate the OFFER, I'll PM ya!!

Thanks everyone for the input, and HE will definitely be getting the wiring checked and fixed before getting this repaired one back in his hands!!
T.C.