how to diagnose blown psu, or, undiagnose it.

drewjustforyou · 01-03-2009, 04:10 AM

while home for the weekend one of my tasks was to replace the PSU of an old (2001ish) emachine. I decided the best way to do this was to get my psu upgrade, and give the emachine a swap with my stock psu (gateway... something, newish, (2008)) I swapped my psu out, powered the computer up, works fine, swapped my old psu with the emachines, no response (same as the old psu). is that as good of a diagnosis as I am going to get? there is no way I can put the emchine psu in my new computer (24+4 connection), also, would it be a problem if I put a 28 pin connection onto a 24 pin mobo? I vaguely remember doing it in the past, but if I didnt, could that be a cause of the failure to power on? (though I didnt even get to bios screen)

thanks alot, and if one of the mods wants to close my other post, I cant figure out how to delete threads, but I noticed it was already modded by vern, so if he just wants to close it out, I've gotten my answers

thanks again again!

-Drew

eyeCpc · 01-03-2009, 05:48 AM

First of all that old supply wouldn't even meet the minimum requirements of any recent board out. What was a 180-250w supply at best? You would need at least an atx 300w not an old AT type underpowered supply just to see a post.

It's likely that other things besides the supply failed on that old of a system. If the board had a battery to maintain the cmos that's probably long gone charly there. The board itself could have easily given out as well.

saltynay · 01-03-2009, 09:03 AM

Wait a couple of days (for it to discharge) then take the casing off of the psu and look for dead capacitors or some other sign of electrical damage.

chesirecat1701 · 01-03-2009, 02:13 PM

Quote:

Originally Posted by saltynay

Wait a couple of days (for it to discharge) then take the casing off of the psu and look for dead capacitors or some other sign of electrical damage.

If you feel up to that task, working on this inside of PSU's isn't a task for the faint of heart. Ahh listen to me, a few days should be long enough for the Cap's to loose charge but either way still take caution

eyeCpc · 01-03-2009, 03:01 PM

Wear a pair of rubber gloves and touch the two contacts with an old screwdriver rather then getting belted across the room! Caps in a supply can still hold a lethal charge and are nothing to play around until properly discharged.

kmote · 01-03-2009, 07:22 PM

I would not recommend fiddling about inside a PSU. But more to the point if the situation is that you have an emachine PC which does not work, you diognosed a broken PSU but you have changed that PSU out for a known good one from your gateway and it is still not working then maybe the emachines PSU is not what went wrong. Or have I got the wrong end of the stick with this one?

eyeCpc · 01-03-2009, 09:30 PM

On any system that old you can easily run into multiple problems at once. bad or dead supply, board, cpu, memory, hard drive, video card, sound card. You may see a newer supply work on an old system like that but don't expect any old supply to run any recent build.

The questions here would be when was the last time it actually ran?, when did it stop and were you running any particular programs at the time? or was it sitting idle to simply switch off on it's own?, or refused to start up at all one day? How long was run daily if even run on any daily basis? could be another question to ask.

All that is rather pointless however since you would better off simply selling or swapping it off as a parts puppy unless you were able to replace the item that failed and run it for how long before... ?

saltynay · 01-04-2009, 06:21 AM

Quote:

Originally Posted by eyeCpc

Wear a pair of rubber gloves and touch the two contacts with an old screwdriver rather then getting belted across the room! Caps in a supply can still hold a lethal charge and are nothing to play around until properly discharged.

I told him to look for visible damage not using a amp meter and testing them directly thats just stupid I would leave it a week then wear rubber soled boots on a rubber mat easier to do then rubber gloves which in my house would never be at hand.

Lexluethar · 01-04-2009, 11:40 AM

Test the 'broken' power supply with a multimeter. That should tell you if the power supply is giving DC to the system board. If it is, look elsewhere for your problem.

eyeCpc · 01-04-2009, 07:03 PM

Quote:

Originally Posted by saltynay

I told him to look for visible damage not using a amp meter and testing them directly thats just stupid I would leave it a week then wear rubber soled boots on a rubber mat easier to do then rubber gloves which in my house would never be at hand.

Who said anything about using an amp meter?

You would isolate your feet and then handle a cap with your bare hands simply because you are standing on a rubber mat? You'll end up cooked royally since that wouldn't protect anybody. Your bare fingers would still be the conductor there unless you plan to handle the contacts with your feet. :rolleyes:

Lexluethar had a more pratical approach there by simply testing the leads coming out of the supply for a voltage reading there without even opening up the supply itself.

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