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Is my new psu busted or am I an idiot?

Last response: in Components
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January 29, 2009 3:24:26 PM

Or both? Personally I think idiot but oh well.

Here's the deal:

I have an older computer that I put together myself from random ass parts back in 2005. It ain't real pretty or effecient but it does work.

I just got COD:WOW only to realize that my video card is too outdated to play it. Bummer I says, well I suppose I could just update the videocard as a temporary fix until I build a new system in a year or so. New card comes, yay! psu is too small, Frick!

So I says to myself, I says, "well you could just buy the new psu for the furture system." Everything else in the current system will be scrapped, but a psu should last awhile right?

So I bought a nice new one:
CORSAIR CMPSU-750TX 750W ATX12V / EPS12V
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006&nm_mc=TEMC-RMA-Approvel&cm_mmc=TEMC-RMA-Approvel-_-Content-_-text-_-

And it finally arrives yesterday (I say finally after waiting a grand total of 3 days. Newegg rocks). But it doesn't work. son of *!

I guess I thought, and my research led me to believe, that as long as the psu was big enough and effecient enough, it really didn't matter what the other components are. Is it possible that my older components are too old to get power from this beast?

proc: AMD Athalon 3700+
mobo: KV8 pro
gpu: radeon 9800 pro (AGP)
ram: can't remember but its 1gig and I think its made by corsair (useful huh?)
proc cooler: its big and blue and uses the same power connectors as a floppy drive. It also sounds like a jet aircraft.
old psu: Rosewill LC-B400ATX 400W ATX
dvd: BENQ dvd dd dw1620

new gpu is a Radeon HD 3850 (agp as well). The KV8 pro only has PCI slots so the idea of agp was just a temporary fix before a system overhaul.

The new PSU doesn't seem to get power to the components. The little LED display on the mobo comes on, but when I power up nothing happens. Well the exhaust fan twitches and a nasty sound like a bug being fried comes out and the system seems like it wants to turn on but nothing else. At this point I get scared and flip the switch. Anyone know whats happening? Nothing seems to be damaged as I'm typing on it right now.

On a side note, I thought it might be just the old mobo that wasn't working with the new psu, so I put the entire system except for the dvd drive back on the old psu and powered up. Everything ran (duh, its the old psu) but the dvddrive did not. Yes, both psu's were plugged in and turned on. Shouldn't a 4 pin connector work with just about every optical drive out there? (tried the same thing with cpu cooler with same result)

HELP! I want to stop digging this hole. Where did I screw up?

More about : psu busted idiot

January 29, 2009 4:40:29 PM

did you use and connect a 24 to 20 pin converter the right way?

i guess your new psu is 24 pins atx and your mobo is 20-pins right?

also use the right 4-pin connector (near de cpu socket)
January 29, 2009 4:53:23 PM

A PSU will not power on devices unless you've connected it to a motherboard and push the power button on the computer (or "jumpered" the appropriate connections on the main 20 (or 24) pin adapter). This is why your DVD drive didn't work when you were using both power supplies.

Like meljor stated, your MoBo probably has a 20-pin connector and your new PSU has a 24-pin connecter. However, the extra 4 pins are on a 2x2 pin connector that can be removed the other 20 pins. Plug the 20-pin connector into the spot where you plugged in your old PSU, and then look for a 4-pin (2x2) connector near the CPU and plug in that 4-pin connector you separated from the main 20-pin.

If you still don't get the machine to power up after checking that you've got all the connectors hooked up correctly, then the new PSU may be faulty. You mentioned a "bug frying" sound which I'm guess it like a loud electronic buzz. Is the sound coming from the PSU? A nasty buzzing sound from the PSU is never a good thing.

You could take the PSU to a local computer shop and have them hook it up and test it if all else fails.
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January 29, 2009 4:54:22 PM

Yeah did all that.

Ray answered that question about 2 psus together, thanks.

As far as that 2x2 that pops off the 20 pin connector, its not nearly long enough to reach the slot by the proc. Not hard to remove the sheath I guess but that seems short sited when manufacturing...

edit: by sheath I mean the nice mesh containment for the wires. This would need to be removed in order to get the 2x2's wires out and enable it to be plugged in a couple of inches away.
January 29, 2009 5:08:55 PM

Also I was using a 2x4 connector that breaks into 2-2x2's for the proc slot. The KV8 manual said that was a 12V1 slot or something like that which is why I didn;t use the 4 pin off the 20pin to begin with. That and the corsair psu manul said something about that pin which led me to believe it wasn;t the right one. Manual's at home or I'd quote it.

The buzz is less important than it seems would be my guess. Its more like a lightbulb blowing out just less loud and alarming. It does not continue.
January 29, 2009 5:45:40 PM

fxgranite said:
Also I was using a 2x4 connector that breaks into 2-2x2's for the proc slot. The KV8 manual said that was a 12V1 slot or something like that which is why I didn;t use the 4 pin off the 20pin to begin with. That and the corsair psu manul said something about that pin which led me to believe it wasn;t the right one. Manual's at home or I'd quote it.

The buzz is less important than it seems would be my guess. Its more like a lightbulb blowing out just less loud and alarming. It does not continue.


no no, the 4 pin for the cpu is NOT the one that is separated from the 24pin. you,ve got it right: there's a different 4 pin connector for that.

never combine 2 psu's in the way you did though, as it can shortcut dat way. send it back for rma and with the new one: remove the old completely before connecting it.

January 29, 2009 6:35:41 PM

sweet so I did manage to get something right.

And I did completely remove the old psu before attaching this new one. It was only after the first one didn't seem to work that I started playing around with it.

So are you saying the new psu I have is defective? As far as you can tell, there's no compatability issues with the hardware?
January 29, 2009 6:50:07 PM

Sorry, bit of a brain fart on that 4-pin connector. Meljor is right, your PSU should have a separate connector for that.

I don't see anything that would cause an incompatibility between your current hardware and the new PSU. If you've connected everything as required then the machine should fire up when you hit the power button.

If you push the power button and nothing happens or the computer fans just kind of twitch then the PSU is probably bad.
January 29, 2009 6:59:35 PM

sweet, thanks for the help guys.

One final question i think:

The 2x2 connection on the mobo over by the proc (whats this called anyway?) can only take a 2x2 connector (duh) but the psu does not have just a 2x2. It has a 2x4 which can then be broken into 2 2x2's. I can only assume that newer mobo's use this config but it can be broken down to make it backwards compatible (again duh).

I assume again that it makes a difference which side I use when I break it apart? I used the one with 2 solid black and 2 solid yellow wires as this is what the old psu had. The other side contained 2 solid black wires (ground I think) and 2 yellow with an orange (red?) stripe on them. The solid yellow solid black side is the correct one right? (and yes I did try both, didn't seem to make a difference)
January 30, 2009 12:34:23 AM

That's simply the 12V connection for newer motherboards which use an 8-pin 12v. Older motherboards used a 4-pin 12V connection, so you can just split that 8-pin connector and use either connection because they provide the same voltage.

I think your PSU is DOA. Probably time for an RMA.
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