Is it safe to use a cheaper PSU with a lot of headroom

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dylankey

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I have used newegg's calculator to determine how much wattage my theoretical system upgrade will draw (about 400-430w depending). I have several small brand, non 80 plus PSUs salvaged from old computers, A couple VIOTEK 550w supplies and a Cheifmax 550w. I know that these cheaper PSUs are not good to build with, as they are known to blow and take other components with them. I have uncovered in my research that most of the time, they run fine underneath what they're rated for, it's when you start pushing them to within 50w or so of their limits that they generally fail.

I'm on a terribly low budget, because I really just need a graphics card to turn my current set up into a gamer, and it seems like a waste to just throw these 3 PSUs out.

SO. My question is, would I be safe using one of these old PSUs to run my system, or do I really need to buy a new one that is 80 plus certified? and if I could use these, which would be preferable?

P.S. I know that newegg is almost always running sales for about $30 on a corsair 400w, 430w, or even a 500w psu that is 80 plus bronze minimum. I'm skeptical of these, since they will be about at the threshhold of my required power draw. So I would likely want to buy a little more power if I can't find the 500w on sale.
 
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Rammy
Ok well there's a couple more red flags on those.

Both of them aren't even close to a modern 550W PSU in terms of capacity, so if you need 400-430W as you originally stated, they aren't at all suitable. Both have a 28A +12V rail, which puts them at 336W of 12V power (assuming you can realistically use it all, which is a big if) - more comparable to a modern ~350-400W PSU.

Also, both say "Select the right voltage" on them. This probably means there is no active PFC, another modern standard and something which is basically mandatory.

Realistically, they are junk. At best they are poorly suited for a modern PC of any type, especially given how cheaply you can pick up PSUs in the states.
Your OP was basically making a case for using an...
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zeyuanfu

zeyuanfu

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I would stay clear of the old PSUs and the CX series. They are known to use low quality parts.
 
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SHADE117

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good quality PSUs are realy cheap on Newegg (compared to German Prices) you could look for xfx PSUs they´re good quality and I often see them at 30-50$
But I would never trust an old PSU with my new Hardware if it does blow it will probably end up costing more than just getting a good PSU
 
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dylankey

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It's important to note that these PSUs are tested and have been used and working, for years. though they've never been gamed on. One was already powering this system with 8gb ddr3 ram, an Athlon II processor, and 2 7200 rpm hdds. (I intend to replace the cpu with an A6 or A8 and add an hd 7770 or gtx 750). I'm not looking for a blanket, "I've been told all cheap PSUs blow up and I'm scared of them, never used them." I'm looking for a professional opinion on whether it's safe.

While that video is convincing, I'm still skeptical as it's a promo vid for Corsair PSUs.

Like I said, I know the knee-jerk reaction is a no. You should never use cheap PSUs. I have researched.
 
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USAFRet

USAFRet

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Yes, that was a Corsair video. They are in the business of selling power supplies. There are others.

And....a bottom end PSU, that has "been used and working, for years"....lends even more to the side of "Do I smell smoke? What was that noise?"

Ultimately, though...it's your equipment. But I wouldn't.
 
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SHADE117

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I believe the sudden increase in power draw when launching a game doesn´t help either VS almost idleing for years and surfing the web etc.
 
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Rammy

Rammy

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Nobody has actually asked a couple of questions which are pretty significant.

1) What are you using this computer for and specifically what components are you using? OC/Non OC etc.

2) Do you have any decent information for your old PSUs? Ie. Specific model numbers, webpages, even the sticker on the side?

The reason both of these is significant is that while using old, no-name PSUs is always a poor choice, it's really hard to tell how poor a choice it is and also to convince you (the OP) of this. PCs have moved to almost exclusively 12V power and old power supplies might only be able to provide 50% (or worse) of their wattage on +12V - and that was when they were new, based on information which may or may not be accurate. Your "550W" PSU could easily be a 250-300W PSU, so your capacity/headroom logic would be deeply flawed.

Secondly, while the likes of the Corsair CX or EVGA "Bs" aren't great for high end machines, they are really solid prospects for lower demand budget systems. When you consider the sheer volume of people using unbranded fire-hazards, they are a much much lesser evil and actually offer exceptionally good value for money when you get them on sale/rebates.

Finally, you don't need an 80Plus certified PSU, it's simply a measure of how efficient a PSU is, and nothing else.
In theory you could replace the transformer/PFC etc in an 80Plus Titanium PSU and make it not comply to even the basic 80Plus standard - but it'd still likely be a fantastic PSU overall if everything else was top notch.
The truth is that 80Plus (even 80Plus Bronze) is incredibly easy to reach these days, even with the most basic of components. Any new PSU which does not have a certification should send alarm bells ringing - not because it'll cost you more money in electricity, but because the production standards are likely to be incredibly low.
 
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dylankey

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This system is actually going to be my girlfriend's rig. She is really strapped for cash and she use it for light to moderate gaming (think 2d platformers, up to maybe like portal 2 and bioshock) and web surfing plus schoolwork. Audio playback and Netflix streaming. She will be using her old tv with a vga as a monitor. it's a fairly big flatscreen (42"? 720p?) No overclock, as she knows less than the little bit I do about system building and I won't be around 24/7 to watch it. We're talking about adding a gpu and upgrading the cpu. The only info I have on the PSUs is what's stuck to the side of them.

http://imgur.com/818igsN
http://imgur.com/XU7t2YS

And on the 80 plus rating system, I'm aware that it's about efficiency, and that's it's incredibly easy to achieve that qualification, but generally, if a company goes through the trouble of getting the certification, the psu will likely be at least decent quality and if it doesn't it's a huge red flag.
 
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Rammy

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Ok well there's a couple more red flags on those.

Both of them aren't even close to a modern 550W PSU in terms of capacity, so if you need 400-430W as you originally stated, they aren't at all suitable. Both have a 28A +12V rail, which puts them at 336W of 12V power (assuming you can realistically use it all, which is a big if) - more comparable to a modern ~350-400W PSU.

Also, both say "Select the right voltage" on them. This probably means there is no active PFC, another modern standard and something which is basically mandatory.

Realistically, they are junk. At best they are poorly suited for a modern PC of any type, especially given how cheaply you can pick up PSUs in the states.
Your OP was basically making a case for using an old PSU with greater capacity than needed rather than buying a smaller capacity new PSU. In reality, all of the new PSUs will have greater capacity than these old models (regardless of the "title" wattage) and even on cheaper models will have some degree of quality.
 
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DSzymborski

DSzymborski

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If you're a gambler and *well* below the actual wattage, you may be OK with a crap PSU. But that difference is a *lot* more than simply 50W. A 700W firebox may be a lying 400W that can handle 250W relatively safely. But there's no way I'm treating a 700W junkcube like a 650W or a 600W or a 550W.

It's not a waste to throw those PSUs out at all. In fact, it's the optimum usage.
 
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