PSU Fried... anything else?

[EndobioticChaos]

This is a problem with some history, so let me list that first.

Not too long ago I built a new machine for a friend. The basics are:

Epox 8RDA+
1700+
512MB Crucial PC2700
Chieftec Dragon case with Foxconn Austin 450W PSU.

Right from the first time I tried to start it up it's had a problem. I got everything set up, all connections done, etc. I hit the power switch... and... nothing. Really odd. Hit it a couple more times and still nothing. So I checked all my power connections... outlet is powered, power to the PSU, PSU switch is on, ATX connector plugged into mobo, CPU fan is plugged in, power button is hooked up right... So I unplugged the ATX connector. At one particular point it somehow made connections, and the fans ran a little. So I plugged it in all the way again, and this time when I hit the power button it fired right up. Great, I thought. Problem solved. And it worked fine... until I unplugged it to move it. Then the same thing happened. I finally decided it had to be the PSU, so I got an RMA and sent it in. Got a replacement, this one being a Foxconn Allied. Hooked this one up, and the same thing happened. So now I'm not sure what the problem is.

Just today we got in some sticks of 256MB Crucial PC2700 ram, and I figured I'd just try one on the odd chance that the RAM might somehow be causing that. (How I don't know, but hey.. worth a shot...) Anyway, we had the PSU removed again (the reason why is another long story..) so I stuck in a new stick of RAM and plugged in just the bare essentials for power connections. Plugged in the ATX first, then I plugged in the power to the PSU and turned on the switch. Then I'm pluggin in a couple case fans, just for good measure, when all of a sudden the PSU goes "WHUMP" or something like that. Smoke is drifting out the back of the PSU, and it obviously was shorted out inside for a split second. I quickly unplugged it. So now my question is "what on earth caused a short inside the PSU?" Is it the same problem that keeps the system from powering on like it should?

Also, it doesn't look like anything else in the comp got fried with the PSU. No scorch marks or anything. Do you think something else might have gotten nuked too, even though there's no visual damage?

I've really run out of ideas here.

[HAL9000]

Very well could be... the only way to know for sure is to test each part individually.... I had a system a while back that a customer brought in... his power supply took out the motherboard, ethernet, floppy drive, DVD, and keyboard.

[Surge1243]

It's very possible that other parts were affected. Some PSUs like to take out the rest of the system when they go. Like HAL said, you'll need to test each part individually...make sure you get a quality PSU for the replacement so that you can avoid this in the future.

[andyms18a]

also check the swich on the front of the case i hade the same prob with intermitent powerups and it was the case switch not making a good conection

[EndobioticChaos]

Originally posted by andyms18a also check the swich on the front of the case i hade the same prob with intermitent powerups and it was the case switch not making a good conection

Good idea, but that's definitely not the case here. First off, the problem isn't intermittent. It does it only when the power to the PSU has been disconnected long enough for the caps to lose their charge. Second, in testing I bypassed the power button by shorting out the two power button pins with a screwdriver.

[Cricket]

Foxconn Austin and Foxconn Allied power supplies are both made by DEER and DEER is considered the lowest of the low in terms of power supply quality. The problem is most likely because of these power supplies. Install a good quality power supply and the system will probably behave itself. Look at Antec, Astec, AOpen, Enlight, HEC, NSpire, PowerMan, Hi-Power, Enermax, Sparkle Power, Fortron Source or PC Power & Cooling for good quality power supplies.

Cricket

[EndobioticChaos]

Thanks Cricket. I sure wondered about that. Somewhere I saw a list of the different PSU's made by Deer, and the Foxconn ones were on that list. I couldn't quite figure that out, because the Foxconn ones have been getting good reviews, while I know the Deer ones stink. I'll test it with an Enermax and see what happens.

[EndobioticChaos]

Well, I finally figured out what was causing the no-power problem, and it wasn't the poor-quality power supply. Apparently these motherboards can't handle being grounded to the case. I used the little cardboard washers that came with the case to make so the mobo doesn't have any contact with the case through the screws. And now it works like a charm.

[EndobioticChaos]

I guess I posted too quickly. The case ground wasn't the problem after all. However, I did determine what the problem is.

The Epox nForce 2 boards all have a USB header to connect front USB ports to. The pins are arranged something like this:

. . . . .
. . . .

On the top row you have: VCC; DATA- ; DATA+ ; GND; OVER CURRENT (another ground).

On the second row you have VCC; DATA- ; DATA+ ; GND.

The case I'm using has front USB ports, which tie into this header.

For some odd reason, hooking up a ground to that Over Current pin fouls things up. That's what was keeping it from powering on. As long as no ground is hooked up there, things work fine. Hopefully this second ground is non-essential. I'll find out in further testing.

Also, it seems the rest of the parts survived the PSU's death; it powerd up just fine. However, I don't have a monitor hooked up to at the moment, so I'll have to check it out more later.