How Does a Computer Power Supply Work (ATX)

Explaining how does an ATX switching computer power supply work. In the next part I'm going to explain how to repair it and what are the most common failures.
Full schematics of many AT and ATX computer power supplies:
danyk.cz/s_atx_en.html
How to modify an AT or ATX power supply to a bench power supply:
danyk.cz/at_atx_en.html
WARNING:
Never open a computer power supply or any other mains voltage device. The mains voltage is dangerous! Risk of electric shock and death. Risk of fire. Leave repairs to professionals. You do everything at your own risk. This video is not an instruction.
You can support me on Patreon:
/ diodegonewild

[@waltercomunello121]

This dude is way too underrated. I love his style, very knowledgeable and natural.

[@mandelbro777]

agree. A man with both a practical and technical mind who doesn't ummmmm-and-urrrrrr like some people on KZbin. A rare combination. He gets to the point, which is refreshing.

[@jun251994]

this comment is way too underated... this comment probably made the guy feel like an astronaut engineer

[@EddieArafa]

I love his accent xD

[@ZaneDaMagicPufferDragon]

I have been binge watching your videos ever since KZbin recently recommended one of your small power supply videos to me after watching a BigClive video and yesterday and today was spent tearing down every single sketchy Chinese electronics device I have ever purchased!!!! Holy Fuck was there some dangerous USB chargers 🔌 with Class X2 1KV capacitors ACROSS THE MAINS AND IN A SPOT THAT WAS CLEARLY MARKED CY1!!!!!! I’m learning a lot about safety from your Super Sketchy Chinese Device Videos and my favorite part is always the reverse engineering with schematics and extremely in depth explanations of what each piece does and why you’re supposed to be using certain components specifically because of safety!!!!!

[@old-schematic]

Engineers who came up with SMPS are real geniuses. Lightweight and much less expensive compared to same wattage transformer PSUs. Got 5 of these ATX for $1 each recently, fixed them, and now they do all kinds of things. One became a workhorse as a lab PSU and the other one to power a homemade coffee grinder motor. As for modding these for any purpose, it's best to learn how electronic parts work in detail rather than doing everything by how-to videos, less chance to make a mistake due to lack of knowledge.

[@saarike]

Really good explained. Thank you very much!

[@SiixthSensse]

In another video I read a comment of how someone first thought you were a joke because you had an accent but gained respect after watching the video. I didn't have sound available on the other video so I couldn't confirm myself. Man o man did I laugh hard when I heard you speak for the first time... However I find this a very informative video. Thank you.

[@antraciet]

Great video. You are more then trained.

[@QuaabQueb]

Very interesting to watch you take it apart and explain how each of the components work and what they do in the circus. Learn a lot this way! Also could you do a video on power factor and power factor correction.

[@Sloxx701]

Good video. Great schematic resources on your site also, thank you.

[@severalkorveks138]

That accent made this video so much more entertaining :D Luv it as well as the transisteeeer

[@rkgki]

Wow! Great video. No wasted words.

[@adithyapillai4259]

It would be really cool to see you tinker around with the feedback and vary the voltage to make a variable bench power supply!

[@crashbandicoot4everr]

That TL494 IC is used on some Betamax VCRs from the late 70s-early 80s. Some machines like the Sony SL-T7 or Sanyo VTC 9455 use a very old style of switching power supply. Also, my 1983 SL-T50 uses this IC on the servo board for the motors. Not sure why.

[@waydejaynes1291]

"No serviceable parts inside how do they repair it then? That's odd." About had me dieing. Thank you for the video really helped

[@franciscosanchez9406]

When it comes to 12 volt 30 amps power supply does it pushes all 30 amps or does it only use on what load needs?

[@sudarapremathilaka1706]

great video tutorial. very clearly explaining all the things.Thanks

[@georgekaramolegos5345]

Great video

[@stefflus08]

Wow, took a look at your page, would I be right in guessing you have a professional interest in computer power supplies? If not you have a very niche geeky passion. Love it.

[@zx8401ztv]

I always laugh at the stickers on any electronic device, they never want you to repair the item and often it can be repaired. I have to rip a new device apart to see how it's been made, i just have to, im nosey :-D The output capacitors looked a bit bloated, that won't help it. I have never looked deep into pfc, but i would expect that inductor is only really effective when the psu is delivering nearly full power. Yes you have some good atx psu schematics on your site :-D

[@DiodeGoneWild]

Yes, they want you to keep buing new ones. They also don't want you to get a shock and then sue them. I will replace those capacitors in the next video :). The passive PFC is just an iron inductor. Of course, the higher the power, the better the power factor. Active PFC is much better, it brings almost unity power factor all the time. But it also adds several more components that are likely to fail. I have seen some ATX's with exploded active PFC MOSFET and a blown fuse.

[@ben--]

The output capacitors look like sam young capacitors. Sam young capacitors are not really notorious (like capxon) but they aren't very good.

[@Mylity66]

Never seen SamYoung caps, but capxon are quite mediocre, I'm sure they will not last anywhere nearly as long as a rubycon or a panasonic but if you keep them away from heat sources and don't force them to their very limits they work nicely. The bronze PSU that corsair sells (not manufacture, they just stamp them with their brand) have Capxon caps and they work a treat. Corsair will of course not slap their brand on a crappy fail-happy OEM PSU, so if it works for them... The problem with these bad quality PSUs is that they always force their capacitors to the absolute limits of their specs, which for bad quality caps is not great because they tend to inflate those numbers. You want really bad capacitors? try "Chang" capacitors, they are absolutely garbage.

[@Mylity66]

The day after my Corsair PSU was off warranty i cracked it open for "cleaning" (visual inspection). I was rather disappointed in the choice of capacitors but the construction quality is a lot superior to other chinese made PSUs (these are OEM made-in-china with a corsair sticker on them after all).

[@ben--]

Mylity 66: There's three versions of that Cheng brand, all three being cheng (which from what i hear is the best of the three), chang and chong (which is the worst of the three with the voltage being one rating lower than the heat shrink says [By that i mean if you use a 50v chong capacitor can only handle 35v before failing, same with their 35v caps only able to handle 25v, 25v caps only able to handle 16v and so on.])

[@Flapjackbatter]

I always thought the 3 transformers between the heatsinks were one each for the 3.3V, 5V and 12V rails. How wrong I was : )

[@hemlocksalad5383]

Nice pfp

[@jeetlodaya775]

Love your videos, keep it up!

[@techandroid3565]

Can you make a inverter using that big transformer from the ATX power supply.(12volt-250V)?

[@ballsrgrossnugly]

When you click on a link in the description and can't help but read the page with the accent. XD And that's not a complaint.

[@juamont]

I cant make up the accent, but the video itself was pretty good, helped with what I needed

[@ilducedimas]

Best accent on youtube, and best content too :)

[@arnauddejarcy4988]

i have a 500w power supply where the small transistor from the auxiliary (5V 2A) has blown way and now I can't read the reference. Anyone has an idea with which reference I can replace it ?

[@toddt6730]

Do you have a video explaining the power circuits of a microwave oven, I'm not understanding why the diode is grounded to the frame

[@shadowwarrior1428]

Love your videos, Question, could a computer power supply, be used/converted to power C.O.B." chip on board" L.E.D." light emitting diodes" if so, how ? I would love to see a video on the topic. Thanks and keep the videos coming !!!

[@MuhammadSalman-be1qz]

My Corsair AX1200 sometimes works for 10 minutes, sometimes half an hour or more and then the computer shuts down. Then it doesn't turn on at all for hours. After a few hours it start working again. What could be the problem

[@DanielsGameVault]

The 3.3v output uses what's called a Mag-Amp if I'm not mistaken....took me a while to figure out how that works :))

[@DavidBTB]

So, when people make bench power supplies out of these and they join all the wires of the same voltage it's all going to the same secondary winding? You just need enough to carry the current, not all 8+ joined together?

[@khayyam741]

this version is most common of the old atx power supplies i-e half bridge with slight differences in 3v processing.

[@roobertmaxity]

awesome video!! very indepth top

[@andrewjones198]

You sir are amazing. I wish I could know half of what you've forgotten.

[@WV591]

Say DGW, one of the best tutorials on tube bar none. TU and SUB

[@Rb39-ej5hh]

Does anyone know what the round black thing, on the bottom right is*? The heat shrink (I think) with the live and neutral wires bunched inside. Do I need to keep it if I want to connect those wires to a regular ATX PSU? * 68kmla.org/forums/uploads/monthly_2018_10/1000.jpg.a7b02415a18ffc97b1f70f3d77e53ce8.jpg

[@kittikajorns1811]

My psu is short circuit, L-N pole has near zero ohm. Which components should I look into?

[@Luiz_inventor]

Everything in the AC part Diodes, Capacitor, varistor etc

[@francismannion7075]

Thank you for a very informative and enjoyable video!

[@lez7875]

saudações do Brasil + like. interessante. aqui no clima temperado dos trópicos + poluição atmosférica = a fontes que duram pouco. sucesso.

[@guitarguy3688]

Thats the video I was waiting for

[@dogeeecart6082]

well i got power supply that says 570w but it can only fully loaded give like 270w.Did i got scammed or?Power supply is MSI ms-570

[@Mylity66]

If one of the internal components of the device fails it has to be replaced by a new one of identical or similar sepcs. So the sticker is actually right, There are no serviceable components inside ;) (Well i guess you could fix an inductor or transformer if you really want to)

[@jeanpierredaviau7478]

Very, very good.

[@gengpan]

good video

[@MrWasim100100]

nice video

[@rahulsagar3068]

Sir make a video on pulse transformer please I want to understand

[@i_g9854]

Thanks for the video Please also make video on !!Convert power supply into variable dc output supply for projects!!

[@avimaurya11]

good vedio

[@josipzlk8019]

how do you explain additional winding in drive transformer that is in series with primary ? Boosting base drive current is that right or is there something else to it ?

[@SianaGearz]

Wait what, where? I can't see one in the schematic he drew.

[@josipzlk8019]

Siana Gearz I am talking about atx supply in general not schematic from video

[@DiodeGoneWild]

Yes, exactly. It boosts the drive current. Like this, the base driver transistors can be much smaller. They more or less carry the full current only for a very short moment when it changes the state.

[@hamcher]

He new what he did , that's the important not the way how he talk ,I like him.

[@itsoshe]

great tutorial bro keep up the good work

[@jimis04]

The last 2 years i have collected over 12 broken ATX supplies thrown in the dumpster. Most of them maby 10 were fixed and most of them chinese with TL494 and KA7500B and 1 or 2 with IC2003/2005 (the chinese who wrote that their is no servicable components inside disliked your video). But i dont want to spoil your follow up video by mentioning the common failures and repairs. Very interested in seeing this video. I am also really really interested in seeing a detailed semi expert video about the so interesting half bridge topology and explaining in detail the various blocks of operation, with oscilloscope references.

[@simonilett998]

Quite a few of those output capacitors didn't look real healthy. I just replaced a few in an atx power supply I bought 2nd hand that were looking much the same. Luckily I ignored the warning label, I opened it up to clean it out and inspect. I was sure to replace those 'dodgey' capacitors before trying to power it on.🤣👍🇦🇺

[@shahara551]

what is the purpose of capacitor 2.2uf on the primary side ?

[@DiodeGoneWild]

It's for DC decoupling. The purpose is that only a high frequency AC voltage can go into the transformer :).

[@shahara551]

+DiodeGoneWild thanks

[@shibinshiji4671]

Sir please tell me about optocoupler it's working on smps

[@franzliszt8576]

It limits the duty cycle to regulate the voltage we want

[@kokotajebka]

The varistor can not work without the inductor here bc there is huge capacitance load ant it transfer voltege spikes (from power line) to current spikes and it help destroy the input capacitors in some time . This varistor should can absorb voltage spikes from the powerfactor inductor while you interrupt AC line when phase shifted AC current in the inductor is on high value . but huge capacitance load transfers this spike into the current spike again.

[@mrm99999]

VERY GOOD ENGLISH SIR.

[@Myrwok_Worzylux]

ppower supply 3+, +5, 12+ to 24v???

[@d.k.9406]

Danke!

[@MrSpacelyy]

So it uses a transformer. I imagined it was switching. It's so tiny, running 30 amps thru that. How is that possible.

[@alibehrouz9833]

you are a kind man thanks for sharing your data plz don't speak about his accent it's a silly job it is important to learn

[@mihailsaltirov5333]

U said ur power supply is old the newest I had buyed has visible solding in the power cable also no inductor just a normall switch

[@TheJavaSync]

OMG ... It's You .. Danyk.cz .. followed your blog for along time a go !!! & Leme ask a question, when it is available 5v standby but no more the other Voltages Output after green & black wire shorted, What should I to do ??

[@Cheese_1337]

TheJavaSync replace the chip :D

[@overbuiltautomotive1299]

thanks i love you help explaining that board hooked to line voltage in frum wall was -line conditioner ---thanks i tapped mine then it started werking new pc go figure ...God bless you Jesus name ....love accent ignore haters i do as i frum tennessee

[@pollydor07]

Thanks

[@hoangnguyendinh291]

My PC power supply does not have the main switch. The CPU fan rotates a bit at the moment I plug it in. For all the years, it's still fine 😂

[@alexbenjamine7576]

where did you get the schematics for that board bro .....i love the video by the way ..keep it up

[@gacherumburu9958]

👍👍👍👍👍

[@myjattapong829]

Wow

[@yogaraj1524]

Thank you sir

[@mnhmgadka4421]

thanks

[@perparimosmani9324]

Wery god moy colegys👌👍

[@mrdesperate6534]

I subscribed just for the lovely accent

[@channelsixtysix066]

"The Small 5V Power Supply Is Quite Boring" - As opposed to the more entertaining 12VDC supply.

[@brahimabdelsadek9534]

You re geniuuuuuuuuusss.keep going pls.nice videos deserve billion dollars.

[@CorruptionCatAU]

the moment you touch the "heatsinks" and realize they arent normal heatsinks. ouch btw... i touched those damn things 2-3 times and i never learn that they are charged...

[@jeimsu21]

I liked the video because of the accent

[@SnailThunder68]

Where are you from? I Love your accent.

[@sam666r]

👍

[@lenaroseguera1241]

What does the transformer sticked on the case?

[@andrewjones198]

He drew the schematic in next video haha

[@richardnanis]

Hi Dan, if you are interested in real big server psu that can deliver up to 6000 or 9000 W (!!!) have a look at the Cisco WS CAC xxxW which is used in Cisco Catalyst 6500 series and others and comes in 3000, 6000 or even 9000 W model! It is also known as Astec Model: AA23340 (as a server psu) but you can find it cheaper as WS CAC ... It delivers 42 volts at 70, 140 or even 200 amps depending on the model/wattage. It is quite easy to manipulate to output 36 ... 52 volts - if you are interested just tell me, i will give you a link with modification instructions ;-)

[@abousamah1967]

شكرا جزيلا دائما محاضراتك مفيده جدا

[@DolezalPetr]

takže ty seš danyk?

[@DiodeGoneWild]

Aha, on to někdo nevěděl :).

[@DolezalPetr]

nechtěl bys nám ukázat nějaký tvoje vynálezy?

[@kokotajebka]

inflated capacitors

[@yukiakahaka1893]

hey cant you make a video about explaining the mean of -5v or -3v,,,, on a powersuplay...

[@yourcreed104]

You just threw all the screws 😂😂

[@shibinshiji4671]

Anybody can help me please

[@edgarkoterle]

"Serviceable components" je možno myslené tak, že súčiastky sú neopraviteľné, nie nevymeniteľné. Ale tak či tak sa zdroje vždy menia kus za kus ako dnes všetka elektronika, bohužiaľ...

[@DiodeGoneWild]

I tak se to může myslet. Chtěj aby se koupil novej, ne se opravoval. A taky nechtěj, aby do toho někdo šťoural a dostal šok. O toho člověka jim asi nejde - oni hlavně neradi, když se s nima pak soudí.

[@widyahong]

How to priming chip in secondary?

[@nirajsomai9957]

Sir please make a video on a dc power supply which contains 2 different grounds Which are Isolated from each other And how to make it. Please please Make a video on it.

[@HDXFH]

Handy for bench use

[@BenjaminKeller]

I like this only for his iinglishh dialect 😂

[@attilaszarka8837]

I bet anything he is from czech republic :DDD

[@dariushunter6792]

That's an old PSU x3

[@dabupk3807]

he talks like helllllooooo my friendddssssssss how are youuuuuuuuuu lol

[@German_byte]

lol "trained personal only"

[@Killerspieler0815]

"A-PFC in "latest eones" = ROFL ... Active-PFC exists since at least 2001 in high(er)-end consumer PSUs ( brand: Enermax )

[@123grobari]

First

[@onceuponfewtime]

are you an Italian?

[@evergreatest7644]

Another "dodgy power supply"