Help with a Dell computer power supply?

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A friend was ready to trash his computer because it seemed to be dead. He'd been told it was the power supply. The computer is a Dell XPS 8300.

He ordered a replacement power supply from an Amazon seller. I told him I'd see what I could do, and today he gave me the computer and the new power supply. (The shipment box hadn't even been opened yet.)

I removed the old power supply, and in putting the new one in, I noticed it had a funny little button next to the power light on the back of the supply, right below where the power cord plugs in.

The original supply, tho' not working, had its green power light come on as soon as the cord was connected.

The new one didn't.

(I also noticed the model number wasn't the same, which makes sense seeing as the new one has that button, tho' otherwise looks identical.)

Anyway, with the optical and hard drives connected to the power supply, and the 4-pin and 24-pin connectors on the motherboard also connected, I plugged in the power cord. (This was when I noticed no light came on.)

I hit the computer's power button, but nothing happened.

Then, I tried pushing the odd little button next to the power light. The light came on, and a minute later the computer was going into Windows. The desktop came up, the programs seemed to run normally...

Then I let go of the weird little button on the power supply.

The power light went out and the computer went dead.

Any idea what's going on here?

Why is it running only with that weird little button held down? Why is the computer's own power button NOT giving the machine power?

Any ideas, guys?

I'm on the verge of trying to buy a Corsair power supply for it, the same one I've used in two computers I built. Think that might be the thing to do?

Thank you.

sounds like a faulty cord to me...it should certainly give the computer power if you plug it in, you shouldn't have to hold a button. Maybe if you go to a dell store or a store that sells them they could give you a proper cord. I mean you can order ok cords off the internet but there isn't much guarantee it will actually work with your computer. Maybe try an look for a cord for the model of dell it is on ebay?

I know a couple years ago I bought a PS3 system and the cord they sent with the controller was messed up, I ended up messeging them and they sent me a new controller because I thought that was the problem at first...but they sent the new controller and it still wouldn't work till I found a random PS3 controller cord in my room. So I figured out it was the cable and sent them a message that their controllers weren't faulty, it was the cord. So I know sometimes stuff like that can happen....but I am sure if you got a functional cord for that model of computer it should work.

I have no idea what that button might be, but maybe it is a reset button for a circuit breaker that will not remain reset like it should. In any case, be sure any other power supply you might get is actually compatible with your specific Dell. At least in years past, Dell did some funny things with pins and wiring so only their OEM stuff would work.

It could also be that some other failing internal component on that PC is causing increased current draw beyond what the PSU can supply without shutting down to protect itself. Check fans rotate freely, and try with as many things as possible disconnected (optical drives, additional hard drives, add-in cards not CPU or GPU fans though). I've had this type of thing from a failing hard drive in the past as well, not easy to diagnose if it's that if the PC shuts off because of it, although if the machine will POST with it disconnected, it might be time to try substituting that for a known good one, if you have a spare kicking round, and see what happens.

Might be worth taking it to a (good) computer repair shop for a "proper" investigation, beyond what I've said to try already, there isn't much a "typical" hobbyist can do by way of diagnosis besides looking for broken components, or obviously blown capacitors, a decently equipped shop will have gear to test the PSU (even new ones have been known to be dead or faulty on arrival, had it happen to me recently, only I had a tester and could definitively spot the fact), means to check the voltages of the various supply rails under load (with the machine booted) for proper voltage, some will have RAM testers, and most will have a range of "known good" components to exchange for elimination purposes.

Not sure I can be any more help at this point.

I tried the original power supply in the second computer I built (which has been sitting around for months doing nothing...if the power supply wrecked it, no extreme loss.)

The computer booted and ran fine...for a couple days. (I eventually restored my original power supply, so the Dell one can be used in that computer again.)

I was satisfied it's not a power supply problem. My friend's sending the replacement power supply back, and I've ordered (and received already) a new board.

Will address the next problem in a different thread, since this one is about the power supply.

Thanks for your replies.