How to tell if a PSU is garbage?

Deniedstingray · May 11, 2017

I always see people ripping apart certain PSU models but i never understood why that is.

Some really good companies such as EVGA and Corsair seem to have some really garbage power supplies but then some really good ones at the same time.

What makes a PSU bad?

TJ Hooker · May 11, 2017

For most people, the way to tell is to look at reviews.

A bad PSU may be inefficient, have poor voltage regulation (keeping voltage constant across as current increases), poor transient response (doesn't handle rapid changes in load well), high voltage ripple, poor hold up time, etc. They also may have poor quality components (particularly capacitors) and/or workmanship, making them more likely to fail prematurely and possibly in a dangerous fashion. They may be lacking some protection features.

RCFProd · May 11, 2017

You look at the brand and model of the power supply, then you look at reviews. You'll find out how it performs and who made it. There are only a few really reputable PSU makers, so the maker will already tell you plenty.

JamesSneed · May 11, 2017

Everything TJ hooker said is what makes a PSU bad. What he eluded to but didn't just say is that all those things lead to instability, early PSU failures, and in the worst case scenarios even killing every single piece of electronics connected to the PSU.

Check reviews here on TH, HardOCP and JohnyGuru. Once you read a review from each of those sites I think you will see what they are testing and mostly see why.

geofelt · May 11, 2017

Vendors like EVGA and Corsair source their power supplies from other manufacturers.
Not all are equally good.
One rough way to tell is to consult a ranking table such as this:
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html
Try to pick a tier 1 or 2 unit. Tier 3 if you really must.

A cheap PSU will be made of substandard components. It will not have safety and overload protections.
If it fails under load, it can destroy anything it is connected to.
It will deliver advertised power only at room temperatures, not at higher temperatures found when installed in a case.
The wattage will be delivered on the 3 and 5v rails, not on the 12v rails where modern parts
like the CPU and Graphics cards need it. What power is delivered may fluctuate and cause instability
issues that are hard to diagnose.
The fan will need to spin up higher to cool it, making it noisy.
A cheap PSU can become very expensive. Do not buy one.

Deniedstingray · May 11, 2017

geofelt :

Vendors like EVGA and Corsair source their power supplies from other manufacturers.
Not all are equally good.
One rough way to tell is to consult a ranking table such as this:
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html
Try to pick a tier 1 or 2 unit. Tier 3 if you really must.

A cheap PSU will be made of substandard components. It will not have safety and overload protections.
If it fails under load, it can destroy anything it is connected to.
It will deliver advertised power only at room temperatures, not at higher temperatures found when installed in a case.
The wattage will be delivered on the 3 and 5v rails, not on the 12v rails where modern parts
like the CPU and Graphics cards need it. What power is delivered may fluctuate and cause instability
issues that are hard to diagnose.
The fan will need to spin up higher to cool it, making it noisy.
A cheap PSU can become very expensive. Do not buy one.

oh yeah i understand not buy a cheap one. I have a 550W Gold Seasonic but i was just curious what makes a psu bad.

What exactly are the "rails"?

TJ Hooker · May 11, 2017

The PSU has several different outputs at different voltages. 12V, 5V, 3.3V, etc. These are referred to as voltage rails. For instance, an important metric is the amount of current a PSU is rated for on the 12V rail.

DSzymborski · May 11, 2017

Here are two useful introductions to PC power supplies.

http://www.hardwaresecrets.com/everything-you-need-to-know-about-power-supplies/
https://www.techpowerup.com/articles//overclocking/psu/160/1

Susquehannock · May 11, 2017

Well said everyone. This whole thread deserves a big up vote.

PSU quality should always be a primary concern. Strategy that has served me very well in near 19 years I have been doing this PC thing.

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How to tell if a PSU is garbage?

Deniedstingray

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DSzymborski

TJ Hooker

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RCFProd

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JamesSneed

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geofelt

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Deniedstingray

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TJ Hooker

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DSzymborski

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Susquehannock

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