Old power supply with new motherboard and build

[doolaford]

I'm helping a friend rebuild a machine, and was going to basically only reuse his case and power supply from a 3+ year old machine...case is similar to an Apevia X-cruiser case, with the power supply mounted at the top. When we were at Frys, the young man helping us told me something that concerned me, and caused us to buy a new Power supply that supports the eps standard vs. the old 420w that my friend's machine has in it, and I'm curious if you can help me understand if he was correct or just trying to sell us a ps...my friend's old ps is a 420w with a 20 pin and 4 pin connectors, not the current 24 plus 8 - we were told that using the 20+4 would eventually short out the mobo, and that we either needed adapters or a new ps, which is the route we chose to go - one other note here is that the new ps is a top-mounted exhaust vs. rear, and this old case has the ps at the top, so i'll have to vent it downward (shouldn't be a problem, right?). I guess that's a long way to this question - did we do the right thing by buying a new ps (cooler master extreme power plus 500w) to go with this new rig (Gigabyte MA785 GMT - UD2H with an Athlon II x4 620 processor, 4 gb of ddr3 ram will be the new specs). Using onboard video, so no big power needs there...

Any advice would be greatly appreciated - both on if we really need the new ps and assuming we do, if firing the fan downward into the case is a problem...

thanks for your advice - this is my first post, so I apologize in advance if I made a mess of how I'm supposed to lay things out.

 

[cmichael138]

The new PSU was a good move. The Cooler Master is a very reptutable brand and is designed for newer motherboards and peripherals. Having the fan blow downward should not cause any problems as long as you have a good exhaust fan.

 

[szbxa]

well, though your psu is old, as long as it's working properly, there's no problem for it to power your new system, it can even handle it if you add a small video card, i don't think that extreme power 500w has 24+8 pin, and that coolermaster psu was a not a high end model as well, u can find it on newegg for like 40 bucks or less, if u just want a new psu that u can keep for long, get a better one, otherwise there's no point buying a new psu.

 

[jsc]

CM is a reputable brand - as long as you are talking about cases. Their PSU's are excessively mediocre.

...my friend's old ps is a 420w with a 20 pin and 4 pin connectors, not the current 24 plus 8 - we were told that using the 20+4 would eventually short out the mobo, and that we either needed adapters or a new ps, which is the route we chose to go

The salesman was either honestly wrong or trying to sell you a new PSU. Either way, he would have done better by pushing you toward a Corsair or Antec PSU.

- one other note here is that the new ps is a top-mounted exhaust vs. rear, and this old case has the ps at the top, so i'll have to vent it downward (shouldn't be a problem, right?).

Many PSU's use a top/bottom mounted fan instead of a back mouted fan. That lets them use a larger fan rotating more slowly (quieter) to move the same amount of air through the PSU. And the fan will pull in air from inside the case and vent it out the back. So, not a problem. It is doing what it is supposed to.

... both on if we really need the new ps

Depending on the brand of the old PSU, a newer one wouldn't hurt, but I'd say you didn't need one.

 

[daship]

He was wrong or lied for commissions.

 

[Onus]

The old 420W, if the one from the Apevia case, was fecal, and good riddance (reviewed at Jonnyguru.com years ago). Using a 20->24 pin adapter on a PSU is a bad idea unless you're running a very low-power system; those extra wires were added in order to carry more current. Without them, you could actually melt the existing wires and/or the connector. "Short out the mobo" isn't what's happening, but give the guy half-credit for knowing it's a bad idea.
Some of the newest Coolermaster PSUs appear to be decent. The one he sold you, unfortunately, isn't. It is an older, inefficient, overrated model. I'd strongly suggest that you return it. The short answer to what to get is a 500W Antec Earthwatts and have done with it. The longer answer is, find a PSU with full range active PFC (no little voltage switch) that is 80+ certified. Antec, Corsair, Seasonic, PC Power & Cooling, and Enermax are among the better brands. A quality 500W PSU should be enough for just about any single video card (except the HD5970).

 

[doolaford]

thanks all for replying - i think what i'll do is see if i can get an Antec earthwatts 430 psu for him - that's closer to his price point and will get us into an 80+ certified ps...

 

[Onus]

Ok. You did say onboard video, so that's certainly big enough. In fact, if he'll NEVER get a high-end video card (e.g. nothing over a HD5760, HD4770, or 9600GT / GSO) you could get him a 380W Earthwatts and it would be enough. Seasonic has some 350W 80+ bronze models that would also suffice for such a system.

 

[jsc]

Or a Corsair 400CX.

 

[Onus]

Yes, or that.

 

[clement4413]

Corsair CX400 the best choice

Lot of connectors,Quiet, Cheap.