What actually makes a power supply bad?

[BryceAC]

G'day,

I understand that choosing a reliable, efficient and powerful enough PSU is extremely important when buying parts for a system.

However, in terms of reliability, what's the main difference between the cheapest PSU off the shelf to one that'll lighten your wallet?

Efficiency, warranty, cable quality and sleeving presumably have an impact on price, but will the cheaper option "explode and ruin your PC" as I've heard many fellow enthusiasts say?

Let me know if you've had any good or bad experiences with cheap PSUs.

Cheers.

[iRileyx]

Cheaper PSU's tend to have cheap/low quality capacitors and other internal parts, which is what makes them "worse" than other power supplies, and more likely for them to break and cause damage to your PC.

@STRMfrmXMN Would be able to give a much better explanation than that though  

[JefferyD90]

15 minutes ago, BryceAC said:

G'day,

I understand that choosing a reliable, efficient and powerful enough PSU is extremely important when buying parts for a system.

However, in terms of reliability, what's the main difference between the cheapest PSU off the shelf to one that'll lighten your wallet?

Efficiency, warranty, cable quality and sleeving presumably have an impact on price, but will the cheaper option "explode and ruin your PC" as I've heard many fellow enthusiasts say?

Let me know if you've had any good or bad experiences with cheap PSUs.

Cheers.

The short of it is that PSU's misrepresent their power output and that they're inefficient.  But, I guess what you're asking is how does this really matter.

 

Misrepresentation:  A PSU is measured in total wattage output.  Watts = Volts x AMPS (@ 1Ohms)...  So the Voltages are predetermined based on the connector, for example your motherboards 24-pin connector is 12 Volts, so if it gives you 10 AMPS it means that your motherboard can retrieve 120 watts of total power.  The point I'm making here is you need to know where your total of 500 watts is going to.  If you buy a 500 watt power supply where it only delivers 50 watts to the motherboard but it delivers a total of 250 watts to the 3.3 volt HDD connectors...  well, yea its still a 500 watt power supply but nearly 225 watts of it is just simply isn't useful.

 

Inefficient: The second problem with bad power supplies is they're inefficient, this basically means one thing...  It's costing you more money than needed.  So that 500 watt power supply mentioned before, in order to produce 500 watts to the components, will actually probably draw about 550 watts from the wall.  That actually is a really good power supply, but in reality, a bad power supply on the other hand will draw about 650 watts from the wall and only produce 500 watts to the system.  The real problem here is that that power being drawn from the wall HAS to be dispersed SOMEWHERE and that extra 150 watts will be thrown out into the air as heat.  So imagine putting a extra FX-8350 in your case worth's of heat.  Or adding a extra GTX 1060 worth of heat...  And you don't get a drop of performance out of it.

 

I hope this outlies whats up with bad power supplies and why they're actually a bad idea.

[it_dont_work]

Misleading power delivery spec as well, I have a psu on the shed (I mean that to it's holding down the edge of a tarp) that is rated for 550watts out of an old pre built, which is rated to provide twice the power on 5v that is can on 12 volts.

[Biggerboot]

It's difficult to tell by specs these days, and generally you don't want to shop by brand.  Each brand has their good and bad PSUs.

It comes down to reviews.  More specifically, reviews that check the quality of the parts and how they perform (efficiency, ripple, noise, etc.)

 

Take the EVGA 500b, which isn't even rated as haswell ready.  You'd think a bronze cert. PSU from EVGA would be up to par, but it's really a re-branded mediocre HEC PSU.

https://www.techpowerup.com/reviews/EVGA/500B/

 

6 hours ago, BryceAC said:

Efficiency, warranty, cable quality and sleeving presumably have an impact on price, but will the cheaper option "explode and ruin your PC" as I've heard many fellow enthusiasts say?

Let me know if you've had any good or bad experiences with cheap PSUs.

Cheers.

We tend to say that because the PSU is the one part that can take all of your other PC parts with it, so it's generally smart to go with a trusted PSU.  It's not very likely to happen, even with a bad PSU, as long as your power is grounded and surge protected (the higher end PSUs will protect your system against dirty power).  But computers with pretty expensive parts in them aren't worth that risk.  

 

Then there are cases of people only going by brand and not by the individual unit.  The corsair CX is the most infamous example of this, because it was an entry-level PSU (marketed as such), that was sold in +600 watt variants.  Not necessarily a bad PSU, but not built for the kind of builds people were doing.  

 

Very rarely is a Corsair PSU going to take your whole PC out (they hold a certain level of standards), but a lot of them died sooner than they should have, and had to go through several revisions to be reliable in a modern PC.  Plus modern PCs have become more efficient themselves, so there's much less emphasis now on wattage and more on quality.

 

This is a good list that rounds up the consensus on well known PSUs: 

 

[STRMfrmXMN]

7 hours ago, RKRiley said:

Cheaper PSU's tend to have cheap/low quality capacitors and other internal parts, which is what makes them "worse" than other power supplies, and more likely for them to break and cause damage to your PC.

@STRMfrmXMN Would be able to give a much better explanation than that though  

Pretty much just low-quality components and poor electrical performance. 

 

7 hours ago, BryceAC said:

G'day,

I understand that choosing a reliable, efficient and powerful enough PSU is extremely important when buying parts for a system.

However, in terms of reliability, what's the main difference between the cheapest PSU off the shelf to one that'll lighten your wallet?

Efficiency, warranty, cable quality and sleeving presumably have an impact on price, but will the cheaper option "explode and ruin your PC" as I've heard many fellow enthusiasts say?

Let me know if you've had any good or bad experiences with cheap PSUs.

Cheers.

What I said above. The warranty often reflects the quality of the unit.

[JonU]

The key to a good PSU is good voltage regulation and good ripple control. Being inefficient may cause you to spend more on the electricity bill and put more heat in the case, but it isn't going to cause problems to components otherwise. Article on Corsair's web site written by JonnyGuru: http://www.corsair.com/en-us/blog/2013/march/why-does-a-better-power-supply-mean-a-better-computer-experience

 

 

[Matias_Chambers]

Bad quality PSU's usually have bad voltage regulation and electrical performance. They also often use cheap Chinese capacitors.  

[Guest]

Bad Components - shorter psu lifespan and increased chance of failure (and risk of frying everything connected to it)

 

Bad Performance - affects your system stabillity and oc. Will also decrease the lifespan of other components as well.

 

Low Efficiency - Isnt as important as other things, but it will result in higher energy bills.

 

Hold-up-time - because the psu cannot stay on (provide power) for a long enough time after power goes out, your computer cannot save the files and it may lead to lost files or corruption. Can be solved with an ups. 

 

Sleeve-Bearing-Fan - Because of its cheap design, it wears out very quickly when mounted horizontally. Not ideal in a psu where its very hard to swap out a dead fan.

 

Safety - some PSUs dont have any protections. If the fan dies for example, chances are, the psu will melt itself and cause a short or even fire. 

 

Interferance - If the cables or other components inside the psu are not shielded correctly, the magnetic field created interferes with other things, like your sound card. Hearing a constant buzzing sound isnt very comfortable.

 

Short Warranty - Most high end PSUs have up to 10 years of warranty. If your cheap 2 year warranty psu dies outside that period, no one will care about it.

 

The list goes on, just buy a quality psu and never worry about it.

[Ashiella]

On December 7, 2016 at 4:22 AM, BryceAC said:

G'day,

I understand that choosing a reliable, efficient and powerful enough PSU is extremely important when buying parts for a system.

However, in terms of reliability, what's the main difference between the cheapest PSU off the shelf to one that'll lighten your wallet?

Efficiency, warranty, cable quality and sleeving presumably have an impact on price, but will the cheaper option "explode and ruin your PC" as I've heard many fellow enthusiasts say?

Let me know if you've had any good or bad experiences with cheap PSUs.

Cheers.

One day, my friend thought he could cheap out on a powersupply to fit that GTX 980 in the build instead of a GTX 970 he bought a logisys powersupply that was like a 750w or some shit and it literally caught on fire and exploded like an s7 it also shorted his motherboard and graphics card. I was just sorta sitting there like, oh, well, that happened.

[BlueChinchillaEatingDorito]

Cheap no name brand electrolytic capacitors, overrated output specs using a underpowered power transformer, just overall bad circuit design. This two part video goes over most of what makes PSUs bad.  

 

 

[Quaker]

On 12/7/2016 at 6:49 AM, JefferyD90 said:

Misrepresentation:  A PSU is measured in total wattage output.  Watts = Volts x AMPS (@ 1Ohms)...   If you buy a 500 watt power supply where it only delivers 50 watts to the motherboard but it delivers a total of 250 watts to the 3.3 volt HDD connectors...  well, yea its still a 500 watt power supply but nearly 225 watts of it is just simply isn't useful.

 

Inefficient:  The real problem here is that that power being drawn from the wall HAS to be dispersed SOMEWHERE and that extra 150 watts will be thrown out into the air as heat.

This is totally incorrect. A power supply's output rating is the amount of power it CAN deliver. But the power supply only delivers the power required - it doesn't push any "extra" power out as heat.

For example, say you have a 500 watt power supply. That means that, at full 500 watt power output, the supply could be drawing upwards of 625 watts from the wall. (80% efficiency)

But if your system is idling and only consuming say, 100 watts of power, the power supply is only drawing about 125 watts from the wall. There is no "wasted 400watts" that's going as heat.

 

On a more general note:

80+ certification means that a power supply has to meet certain minimal standards, including efficiency, but also involving specs for ripple voltage, overvoltage protection, etc.

Basically any 80+ certified "bronze" power supply meets these minimum standards - which, btw, are chosen based upon the requirements of the digital circuits they'll be powering.

 

Of course, some power supplies may have faulty components or other problems that cause them to fail, but generally speaking any 80+ certified is good enough for general use.

 

It's best to stay away from any non-certified power supplies because if they can't or won't be certified they could be very inefficient and cheaply made.

 

On the other hand, if you are going to do a lot of overclocking, etc, it's good to get the extra stability and features of an 80+ "gold" or "platinum" supply.

 

And, it is, of course, possible to make an 80+ power supply that forgoes extras like sleaving, paint, quiet fans, etc, to reduce cost (and price).

 

[BryceAC]

Thanks for all of your responses.

It was interesting to learn how the efficiency worked in that cheaper PSUs can draw more from the wall than they output.

I think I'll do some research into the voltage rails across different power supplies. 

Cheers. 

[JefferyD90]

9 hours ago, Quaker said:

This is totally incorrect. A power supply's output rating is the amount of power it CAN deliver. But the power supply only delivers the power required - it doesn't push any "extra" power out as heat.

For example, say you have a 500 watt power supply. That means that, at full 500 watt power output, the supply could be drawing upwards of 625 watts from the wall. (80% efficiency)

But if your system is idling and only consuming say, 100 watts of power, the power supply is only drawing about 125 watts from the wall. There is no "wasted 400watts" that's going as heat.

 

On a more general note:

80+ certification means that a power supply has to meet certain minimal standards, including efficiency, but also involving specs for ripple voltage, overvoltage protection, etc.

Basically any 80+ certified "bronze" power supply meets these minimum standards - which, btw, are chosen based upon the requirements of the digital circuits they'll be powering.

 

Of course, some power supplies may have faulty components or other problems that cause them to fail, but generally speaking any 80+ certified is good enough for general use.

 

It's best to stay away from any non-certified power supplies because if they can't or won't be certified they could be very inefficient and cheaply made.

 

On the other hand, if you are going to do a lot of overclocking, etc, it's good to get the extra stability and features of an 80+ "gold" or "platinum" supply.

 

And, it is, of course, possible to make an 80+ power supply that forgoes extras like sleaving, paint, quiet fans, etc, to reduce cost (and price).

 

you didn't read my post. The heat comes from the EXCESS power DRAW; not the excess power output, because there is no such thing.

[Quaker]

10 hours ago, JefferyD90 said:

you didn't read my post. The heat comes from the EXCESS power DRAW; not the excess power output, because there is no such thing.

Your wording seemed to suggest that you would always get about 150 watts of "excess" power draw, but that would only happen if you were actually drawing 500 watts.

If you are only using about 100watts there's only about 25 watts of "excess" power.

 

In any case, this is normal. It's why the power supplies have a fan on them.

Most power supplies exhaust their heat out the back so "imagine putting a extra FX-8350 in your case worth's of heat." doesn't actually apply.

 

[JefferyD90]

9 hours ago, Quaker said:

Your wording seemed to suggest that you would always get about 150 watts of "excess" power draw, but that would only happen if you were actually drawing 500 watts.

If you are only using about 100watts there's only about 25 watts of "excess" power.

 

In any case, this is normal. It's why the power supplies have a fan on them.

Most power supplies exhaust their heat out the back so "imagine putting a extra FX-8350 in your case worth's of heat." doesn't actually apply.

 

Exactly, and that excess power, no matter the amount, MUST be disbursed somewhere.  Typically that heat goes straight up into the case.

 

And the point I am making about adding another high TDP CPU is still true, because it IS in the case.  The point I'm making here is that its just more heat for you to have to worry about.  A 500watt PSU with a 150watt overdraw is in line with a 70% efficiency rating...  Which is awful.  Even if you could get that to 80% (a PSU that would cost like $5 more, in theory) you'd be looking at only 100watts of extra heat.

[Quaker]

12 hours ago, JefferyD90 said:

 Typically that heat goes straight up into the case.

No, typically it's exhaust out the rear of the case by the fan in the power supply.

[JefferyD90]

4 hours ago, Quaker said:

No, typically it's exhaust out the rear of the case by the fan in the power supply.

But regardless there is heat there... I mean just exhausting it out the back of the case means the ambient air around the case is warmer...  And hotter PSUs mean hotter components inside the PSU meaning a worse performing and shorter life part.

 

You're making it seem like more heat isn't bad.

[Quaker]

20 hours ago, JefferyD90 said:

You're making it seem like more heat isn't bad.

You are talking about the ordinary heat that is given off by ordinary computers as if it's something bad. For most people, a little extra warmth in your room isn't a problem.

 

[JefferyD90]

10 minutes ago, Quaker said:

You are talking about the ordinary heat that is given off by ordinary computers as if it's something bad. For most people, a little extra warmth in your room isn't a problem.

 

the hotter the part, the less life it will have. Period.

[Quaker]

Also not true.