Do I have a dead PSU here?

IcarusSC

Gawd
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Apr 19, 2006
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Posted in Power Supplies, but I got no responses, so I thought I'd try here.

So a few years back a friend gave us a new Dell Vostro 410 as our kitchen computer. It's worked fine for email and web and a few games for four years. Last week it seized up and wouldn't boot.

I took it apart, cleaned it, reseated the RAM, and tried disconnecting the individual components ... nothing.

When I press the power button, nothing at ALL happens -- no beep, no fan spin, nothing. But the LED on the power supply is on when it's plugged in, as is the LED on the mobo. Is this a dead power supply? Or a dead something else?

Thanks in advance for any and all suggestions!
 

Dangman

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Hit up the stickied "Basic Troubleshooting Guide" on what to do when the PC does not POST. Report back when you've followed ALL of the steps.
 

timta2

[H]ard|Gawd
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I'm pretty sure all of the newer Dells use normal ATX power supplies (Older ones until mid/late 2000's used proprietary wiring scheme). You could get a cheap one or borrow one from someone and plug it in. There could also be a problem with the motherboard so I wouldn't use a nice or expensive power supply to test. :)
 

jojo69

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Hit up the stickied "Basic Troubleshooting Guide" on what to do when the PC does not POST. Report back when you've followed ALL of the steps.

really, do this, you might figure it out yourself in the process and if not we will have a lot more information to work with when you come back
 

nuttcase21

Limp Gawd
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do yourself a favor and buy a psu tester as well. they can be had for as little as $10 shipped and alllow you to plug in all the power cables and test to see if anything is fried. best money i've ever spent on a psu.
 

IcarusSC

Gawd
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OK, so I have to confess that I'm not 100% sure how to short the power switch. I stripped a section of the two wires leading to the switch and held them together ... is that enough to see if it's working? I'm a total ignoramus here ...

Also, I had no idea that PSU testers were so cheap. I'm totally picking one of those up. I'll have to see if I can find one here (in Shanghai) or I'll be waiting 6 months to get one.
 

XenIneX

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Those cheap power supply testers are mostly useless. They can't see problems while under load, which means they're incapable of telling you if a power supply is any good. The cheapest way to test a power supply is to swap it with a known-good power supply.
 

Dangman

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OK, so I have to confess that I'm not 100% sure how to short the power switch. I stripped a section of the two wires leading to the switch and held them together ... is that enough to see if it's working? I'm a total ignoramus here ...
.
Which power switch are you talking about?
 

jojo69

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OK, so I have to confess that I'm not 100% sure how to short the power switch. I stripped a section of the two wires leading to the switch and held them together ... is that enough to see if it's working? I'm a total ignoramus here ...

Also, I had no idea that PSU testers were so cheap. I'm totally picking one of those up. I'll have to see if I can find one here (in Shanghai) or I'll be waiting 6 months to get one.

STEP AWAY FROM THE PSU!

UNPLUG THE AC CABLE AT THE WALL!

EXPLAIN TO US EXACTLY WHAT YOU DID!
 

IcarusSC

Gawd
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OK I HAVE DONE SO!

I followed the stickied guide, which says to disassemble the components and test them individually.

Step 4 of the guide reads thusly: Power on the system using a spare power switch or by shorting the two power switch leads for a few seconds or less (typically done with a screwdriver). Some boards have on-board power switches.

The Dell mobo has no onboard power switch, of course, so I figured I'd need to "short the two power switch leads." I don't know how to short, so I looked it up online and guessed that I was being asked to bypass the switch and power the system on manually, so I followed the wires to where they met up with the power button on the front. I stripped about 1 cm of sheathing off of each wire and held them together. If I was correct, that should have completed the circuit to boot it.

But nothing happened. So I unplugged it again and came here.
 

Dangman

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You weren't supposed to do that. You were suppose to remove case power switch cable/connector/plug from the motherboard. That doesn't require ANY stripping at all. Once you removed/unplugged that cable/connector, that would have exposed a row of pins. If you look carefully at the row of pins, it would have denoted which ones where the power pins or leads (Power+). Then you could have just connected the two leads via a screwdriver (hence the screwdriver reference) and that would have "jumped" the PC. Nowhere does it require you to "strip" any of the sheathing on the cable. And you have damaged the case switch when you did that.
 

jojo69

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Whew, sorry about the caps

from your post I was unsure what you were doing and there are dangerous voltages inside the PSU

sometimes it is hard for us to step back and explain clearly to those with less experience with this

step 4 could be more clear by specifically referring to the motherboard power switch pins, fortunately you can probably just put a pinch of tape on your stripped bits and it will be ok, step 4 is meant to eliminate a bad switch as the problem

god I'm glad you were not inside the PSU
 

IcarusSC

Gawd
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609
Why, yes, that would have been clearer :-D And I figured I could tape it back up, so should be no permanent harm done.

Well, there were warnings all over the PSU with things like "NOT FOR SERVICE" "DANGER" "DO NOT OPEN" "STAY AWAY FOOL" and so on, so I stayed away.

But I still have a dead machine, I think. The funny thing is that when I plug it in, I get lights on both the PSU and the mobo.
 

IcarusSC

Gawd
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No, I didn't yet, because I'm clearly getting some power from the PSU, otherwise why would the lights turn on? I figured I could skip the PSU steps because of that ... am I wrong? I figured it had to be mobo or cpu.
 

jojo69

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I want to hear if the PSU fan spins up when you paperclip pin 14 to ground.

Do you happen to have access to a multimeter?
 

Cypher-

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I know you are in the process of diagnosing this however I will tell you I had the exact same thing happen with my aunts computer and it was the power supply. I had another one lying around so it was a quick thing to test and fix.
 

IcarusSC

Gawd
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Sorry for the delay -- Thanksgiving and the stuff that surrounds it had me distracted for a while.

YES, the paperclip trick worked ... sort of. The fans spin up, but then spin right back down (if I hold the paperclip there). Is my PSU is, in fact, still viable, and this is some sort of failsafe that's keeping it from running ... or what? What does it mean if the fans start and then stop again?

Thanks for helping me stick with the guide; sorry, I can be a bit dense :-P
 

HeavensCloud

Oswego, not shitty as Buffalo
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The fans spin when you short the connection between the green and black wires but slowly lose their power with the paperclip still in the same position? Dead Power supply. Shorting it like that turns the power supply on period - ignoring all fail-safes.
 

HeavensCloud

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I'm no electrical genius but it sounds like the fans are drawing power from the capacitors and something is not charging them back up at the appropriate rate.
 

flyingears

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If you have a cpu thats trying to sense a motherboard then it could be the motherboard. Best bet is to buy a new psu from somewhere close try it on the motherboard and return it if the computer still doesnt work
 

IcarusSC

Gawd
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Thanks for all the advice! I'll try to pick up a PSU from the electronics market near(ish) my home this weekend and see if that does the trick.
 

jojo69

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If you have a cpu thats trying to sense a motherboard then it could be the motherboard. Best bet is to buy a new psu from somewhere close try it on the motherboard and return it if the computer still doesnt work

uhhh, read the thread

he had a paperclip between pin 14 and ground
 

IcarusSC

Gawd
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Just wanted to thank everyone again for their help. I swung by the local electronics market yesterday, and after some bargaining (at which I completely fail ... gah, I hate non-fixed-price retail models), I picked up a new PSU. It's some weird Chinese brand, of course, because my little market never has the good stuff, but at least it was cheap, and the seller promised a refund if it broke.

It took me an hour or so to get everything reassembled because one of the wires in the front-panel power switch snapped, but I eventually got it spliced with the help of an engineer friend of mine and when I put it all back together and pressed the button, it turned on. Hallelujah :)

Couldn't have done it without this forum (well, I probably could have, but it would have taken way longer and I wouldn't have learned all this cool stuff). Thanks a ton. This is why I love [H].
 
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