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why does your computer need a power supply anyway

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you've already got tons of power coming right out of the wall

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oh it blew the fuse

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that's why but why didn't this work

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and what does a power supply actually do to answer those questions we'll be

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taking you through all the stages of your computer's power supply and how

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they work sponsored by seasonic from the

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wall you get alternating current or ac power which historically has been

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cheaper to generate and efficiently transport over long distances which is

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great but not for a computer computers work by

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storing ones and zeros in logic gates and for logic gates to function a very

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stable input voltage is required ac which goes from positive to negative

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voltage many times a second could be

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used but it's kind of like how you could also build a car with square wheels

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you shouldn't so then our wall ac power needs to be

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converted to direct current or dc which

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has a constant voltage no problem

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let's talk about linear power supplies

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from the wall you're getting either 110 or 220 volt ac power since we're in

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north america we'll be using 110 volt for our examples now that is still a way

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higher voltage than what you want for your computer so the first major stage

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is a transformer that takes us from 110

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volt ac to 12 volt ac transformers are relatively simple

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when ac current travels through a wire it creates a magnetic field this

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magnetic field can be made much stronger by wrapping the wire into a tight coil

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and then if you place another coil right beside it the changing magnetic field

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will start moving the electrons in the second wire that voltage that you get on

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the second wire is then determined by the number of turns in each coil so to

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take our 110 volt down to 11 volt we

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could have 100 turns on the primary side and just 10 on the secondary once we're

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at a more manageable voltage we're ready to turn that ac into dc using

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a rectifier rectifiers work on the basis that diodes

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only allow electricity to flow in one direction so you chuck ac through it and

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it spits out something a little bit like this

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you just add a capacitor and bam dc now

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the formal name for this circuit right here is single diode rectifier but more

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commonly in electrical engineering circles you'll hear it referred to as

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crap that's where something called a full

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bridge rectifier comes in for a more detailed look at the full bridge

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rectifier you can check out this classic from electroboom but we can get you

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through the basics by using four diodes in this configuration on the positive

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wave electricity flows through diode one and three to complete the circuit and

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then on the negative wave it goes through diodes two and four that leads

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to much less waste then from here you

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just chuck a capacitor on the output and

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boom you're good to go linear power supplies are actually still

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used for many things including musical instruments thanks to their ability to

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deliver very clean power but unfortunately you wouldn't want to

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use one for your computer due to their 60 plus turd efficiency rating and then

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there's also the fact that they only work for a single input frequency and

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voltage so power supply manufacturers would have to make completely different

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models of the same power supply capacity

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for every different market so

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wait a second why did i just explain linear power supplies then

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because someone had to give them the background that they need for this next part about what we actually use

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switching mode power supplies let's take a journey through your psus starting at

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where the ac enters and leaving you know

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where the dc goes to your motherboard before we can even worry about

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converting from ac to dc we need to do a bit of filtering so these little blue

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boys in here they are called y capacitors and the gray one right there

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that's an x capacitor these guys prevent your computer from sending electrical

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noise back into your house wiring which could cause problems with other devices

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meanwhile we also have to filter the incoming power so your computer doesn't

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get all screwy when your roommate fires up the blender to make some margaritas

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my favorite part of this emi filtering stage is hidden in here it's called a

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metal oxide vary resistor or mauve and it's cool because this changes its

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resistance based on the input voltage so normally it's just chilling there acting

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as an open circuit but when a voltage spike comes in its resistance drops and

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that extra energy just gets chucked to the ground instead of you know blowing

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up everything else in cheap power supplies the mob might be omitted and if

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it is you should emit that power supply from your parts list once the signal is

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clean we can turn our attention to power factor correction as ac flows through

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inductors or capacitors the voltage and current will get out of phase with each

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other resulting in wasted energy this bank of mosfets and bagel inductor make

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sure that you get as much from your ac input as possible at which point is

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chucked through a rectifier right there and out of that you get three to 400

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volts of dc next these big chungus

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capacitors smooth out the voltage of the dc current flowing from the main bridge

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rectifier and side note i would strongly recommend not looking these

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now let's talk about the most surprising part we've gone from ac which comes from

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the wall to dc which your computer needs and now we're going to go back to ac

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and stay with me here because the payoff is huge to do it we run dc through our

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mosfets that are right there giving us ac power but in a square wave which is

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fine except that every time that a mosfet gets turned on or off you lose

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some efficiency to almost entirely reduce these switching losses a

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technique called soft switching is used so in parallel to these mosfets is a

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capacitor and an inductor that will begin to resonate as the mosfets are

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switched the resonator creates a sine wave and by syncing up the mosfet switching

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to when the sine wave is close to at zero you can almost entirely eliminate

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the switching losses i'm not even going to pretend how to understand the math

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behind how this works but if you think you've got the stuff here's a paper to

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enjoy as part of your phd in electrical engineering long story short we now have

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ac power again but it's perfectly power factor corrected and at a much higher

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voltage and frequency compared to what's coming out of your wall this allows the

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main transformer right here to be both much smaller and a lot more power

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efficient as it converts into 12 volts ac which is then fed into the rectifier

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right there and you have 12 volts dc for your pc

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for those of you paying very close attention that was it we finally came back around

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to how your computer uses a linear power supply but not quite like we talked

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about before just with extra steps hey there it is i knew we were gonna

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make it back here then we take that 12 volt dc and we add some hefty capacitors

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for filtering and to improve transient response

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in layman's terms this 3300 microfarad

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capacitor here is going to do a lot to prevent a voltage drop if your rtx 3090

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decides it suddenly needs 500 or 600

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watts for a few milliseconds not everything in your pc uses 12 volt

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however so we also need these dc to dc

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buck converters to get us 3.3 and 5

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volts giving us everything we need to run a computer except

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the ability to turn it on see this other mini transformer over

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here this little fellow takes our high voltage dc from before and turns it into

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5 volt standby which is always on even when the computer is turned off allowing

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it to power things like motherboard RGB and always on usb charging ports

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oh right and also it powers the power button so that you can fire up your

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machine and get on with important tasks like visiting ltdstore.com where we have

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great merchandise like these high quality t-shirts fantastic water bottles

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and even but none of that really explained why good power supplies can

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cost anywhere from one to five hundred dollars something you've probably heard

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talked about in community forums and even power supply marketing is component

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quality with japanese capacitors coming up a lot but do they even make a

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difference these days probably not

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but that doesn't mean they're a bad thing between 1999 and 2007 there was a

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capacitor plague where capacitors made in taiwan experienced a higher than

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expected failure rate due to issues with the raw materials used to manufacture

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them while capacitors in japan experience no such problems

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since then capacitors made in china and taiwan have greatly increased in quality and the

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vast majority of japanese capacitors are just japanese branded capacitors they're

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actually manufactured in china with that being said there is still some

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value to japanese capacitors because typically they are designed and tested

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to meet the quality requirements laid out by the japanese companies overseeing

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their production to figure out if any individual company is good though tom's

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hardware created a capacitor tier list that you can reference when trying to figure out if a specific component is

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good or not the overall capacitance of your power supply can be a double-edged sword

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though one thing people often get wrong is automatically assuming high

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efficiency equals high quality but unfortunately this isn't always true an

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easy way to boost the efficiency of your power supply is to reduce the capacitance you no longer have to worry

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about charging up those big old caps so you waste less power but you could fire

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up a game and end up rendering nothing but a black screen and do we have

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hardware info computer

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and that my friends is why you don't buy your power supply on aliexpress.com

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evaluating how different power supply manufacturers have balanced efficiency

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and transient response is beyond the scope of this video but we wanted you to know that filtering

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by 80 plus rating and sorting by price isn't the way to go low capacitance can

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also be a problem for small form factor power supplies there's simply less space

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to add capacitors in general this won't be a problem but if you're building an

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sff pc that is high powered maybe consider over speccing the power supply

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a bit just to be on the safe side also to be on the safe side never mix

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modular cables between two different power supplies even if they look

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identical there's a chance they are different and if they are it's magic

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smoke time it's always bothered me why they aren't standardized though and i

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was finally able to ask turns out the answer is pretty simple everyone

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developed modular power supplies around the same time and the connectors were

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almost arbitrarily chosen by each company based on their current pcb

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layout and the connectors easily available from their suppliers maybe

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modular cables can get standardized if the specs change

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and there is a good chance the spec for power supplies could change soon the atx

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standard has only gotten relatively small revision since it was created by

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Intel way back in 1995 and there are some problems with this like power

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supplies in 2020 needing to output 3.3 and 5 volts despite these voltages

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barely being used by modern hardware but this could be changing soon in june

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2020 version 2.53 of the atx standard

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was added where the power supply would only be delivering 12 volts and the

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motherboard would be responsible for dc to dc conversion as i showed in this

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video this should result in significant real-world efficiency improvements

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especially at idle but the people we talked to wished Intel had gone even

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further and switched to 24 or 48 volts like you might find in industrial

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applications basically higher voltage means less

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current at a given power and less current means less heat generated and a

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higher efficiency which brings us to the final reason why buying a quality power

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supply is a good idea good old mother earth as much as electronics makers try

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and put a positive spin on their environmental progress apple

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pretty much every component in your pc will offer up mediocre performance in a

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few years or be downright broken high quality power supplies though can last

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you through multiple upgrades see sonic the sponsor of this video has up to

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freaking 12 year warranties on some of their units so at least that's one part

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that won't end up in a landfill anytime soon so huge thanks to sonic for

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sponsoring this video providing us with technical support for this piece and

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thanks again to johnny guru for his insight as well thanks for watching this

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video and if you were looking for another turbon i can't do it

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and if you're looking for another turbo nerd video maybe check out how

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motherboards work turbo turbo nerd turbo nerd is so hard to say

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fast yeah you chucked it twice in the same sentence alex killing me

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i'm done i'm out