Howto repair switch mode power supplies #2: Stand-by circuit and its functionality

[@kiswahilikitukuzwe2547]

Much respect and appreciation from Kenya for the time, dedication and patience you have put in this wonderful series to impart this invaluable knowledge in such a simplistic and holistic way!!!

[@remyxblonay475]

As electronician I never had such good explanation. Many thanks for this unvaluable help for the repair of my switching power supply.. BR from Switzerland

[@DonkeyLearningIT]

Thanks for taking your time and commenting. Also, I am glad that you found the content useful! Wish you a happy new Year from Österreich!

[@sigataros]

very cool job title

[@Ian.Valerio]

My mind is blown! I can watch this all day! Thank you for your work sir!

[@iRevnant0420]

Yes sir, you have definitely got a follower here. Your videos are very high quality and you're teaching is perfection itself. No pretensions, either. You're a true inspiration for DIY. And I love that your videos come in bit size lengths, too. Keeps all that I am learning fresh and within my ADHD limitations. (Honestly, my attention span is barely better than a kitten's, you are great at meeting my need for clarity and brevity!) Thank you from the bottom of my heart. Also, greetings from Arizona, U.S.A.

[@DonkeyLearningIT]

I really appreciate positive comments, many thanks! My original idea was indeed to produce a set of easy to understand videos, but still go a bit into theory and details, just enough so one can understand what is in an SMPS, and why are things solved in a way they are. I have never been in Arizona, but otherwise I loved the desert in Nevada where I spend there a week. I guess Arizona is somewhat similar, or I am totally wrong?

[@fu5ha_edits]

@@DonkeyLearningIT Arizona is indeed extremely similar, lived there for 20 years :D

[@shvideo1]

Excellent tutorial. It is so refreshing to get the facts so clearly explained in order to understand the process. Thank you so very much for taking the time to make these great series.

[@edpax14]

You're a Legend!... very well explained.way better than any professor in the university...well done! Liked and subscribed!

[@DonkeyLearningIT]

I appreciate your positive comment! As for the university, I had good professors, and I had not-so-good ones as well. The good ones are often old in their 50s, and they did not try to be politically overly correct, but instead they tried to teach us useful things.

[@lucam9668]

This is the real deal of power supply basics! Thanks man.

[@peterduxbury927]

I am very pleased to find your tutorials and follow your simplistic way of dealing with the complex SMPS. I always wondered how ANY transformer could function on DC - following rectification. You made this very clear that the Standby Transformer can operate because the primary of the Standby Transformer is receiving a PWM from the Standby Controller IC! I am currently working on a SMPS for an expensive Home Theatre System with a power supply fault.. Quite simply put, there is no output voltage on the secondary side of the Standby Transformer. I have reached the conclusion that the problem may be the transformer itself, or the Standby Controller IC (which feeds the Standby Transformer) is not oscillating. Thank you for passing on your knowledge to those less fortunate. It is also common to discover that many IC's which are found on failed SMPS may have become 'obsolete' - or extremely hard to obtain. This can be a major setback in the repair of any SMPS. As an enthusiastic amateur, electronics have been a great hobby for the past 50 years. I will follow all of your vids from this moment on...... Thank you for your invaluable help. Greetings from Australia.

[@DonkeyLearningIT]

Thanks for taking your time and providing valuable feedback. When it comes to SMPS, even in the case of stand-by circuits the transformer *very rarely* fails. Most of the time is either capacitors, power semiconductors, or controller ICs in this order. I would check whether the controller IC is being powered, and also I would check whether the FET feeding the stand-by transformer is fine or busted.

[@Patron426]

Your explanation amuses me. It's so entertaining. I love it. Thanks.

[@eletro_doc9529]

Your videos are so educational. And you provide them free of charge. It is truly a masterpiece. Thank you very much.

[@haxensalat]

Finally I've found something where someone is telling me exactly what's going on and how to handle broken electronics. Thanks lot for that!!!!

[@DonkeyLearningIT]

Thanks for the comment! As you can see, I am taking a very unpopular approach of trying to educate people about the fundamentals first. This is of course "boring" but this boring knowledge is a *must have* for repair technicians to be successful in the long term.

[@haxensalat]

@@DonkeyLearningIT It's not boring, it's a very practical way to teach. I can't get enough of this. Even, for some cases I would like to get some deeper understanding :)

[@mynameismynameis666]

great material, very straightforward, well constructed and no bs tangents

[@getknowledge450]

Thanks a lot for the well done job. Please keep it on in this manner.

[@DonkeyLearningIT]

Thanks for the good words. Watch part 3 as well. Today or tomorrow I upload part 4.

[@Sirvirgilio]

Wow, really good, really basic but highly informative and well prepared presentation. Thanks for sharing your knowledge. Well done. I cant wait to see the rest of your series.

[@misterbonzoid5623]

I'm learning a lot. A bit repetitive about the bifurcation seeeerkwitt but thanks for uploading. I did electronic repairing for 14 years, but never SMPSUs. Now I want to learn them too.

[@DonkeyLearningIT]

Thanks for the feedback. As the ancient Greeks used to say: Repetition is the mother of all skill and knowledge ;) Though, I agree, on a video platform like KZbin indeed I should reduce repetition, since this is not a school class for repair technicians.

[@khordad1216]

Absolutely wonderful videos! Thank you for sharing your knowledge!

[@xique502]

Thank you so very much, after watch 3 parts of your lessons, I sort of understand why my Samsung lcd TV keep clicking on/off. I followed some videos changed two bad capacitors, it did not fix the problem, even worse, it did not response to turn off signal. I learnt from your lesson, got to check the stand circuit voltage 5 V somewhere, may be after diode just like your picture? Your Donkey Learning IT is doing good for our society, improve people's education level, learning hot to fix computer, TV, reduce wast.I.knew some universities have programs to help people to learn how fix appliances. Keep your good work!

[@hazimjfk]

thank you for this fine detailed lesson and would like the others showing vidz to do it the same way too ... keep on the good work

[@DonkeyLearningIT]

Thanks! Just keep watching the other videos in the series as well (this weekend I will upload the 6-th) because you will learn from the series

[@milkaimwaga-ju7gh]

You earned yourself a new subscriber!!! ❤❤❤

[@karimmahmoudy-uu8ju]

I'd like to thank you for all your perfect videos which helped me alot to get a concept about the boards and also repaiting them. I want to ask you a, question about polyester capacitors. How do they perform like a transformer. I mean in some boards we are having them instead of tranaformer. How can they decrease voltage level. Thank you

[@norwoodd]

Should make these video's mandatory for all incoming electronic students.

[@RaduFilip85]

Congrats ! best explanations from now. I.ve just short circuited the water cooled atx power suply(for my silent server) and is only have stand-by 5V. Now I.m trying to troubleshoot it and the third video will definitely help me to do that. so realy looking forward and again Thank you for the good job done. Maybe the video no. 4 will show how to transform a computer power source in a variable voltage source 0 V up to whatever can be obtained on the operating frequencies, maybe 30 V or so...with hopefully 5 A for a supposingly 400 W power supply. Thx again.

[@DonkeyLearningIT]

Salut! Firs of all with a watercooled PSU one need to be *very* careful, because it cannot leak even a drop during/after you repair it. Otherwise the consequences are really-really bad. What did you shortcircuit btw? Jusk asking because it will help you a lot with the repair knowing roughly what to look for. What I would do if I would be you is to measure the Schottky diodes on the secondary side with a multimeter in diode tester mode. In the case if your PSU uses FETs instead of Schottkys for synchronous rectification, measure the Drain-Source resistance of the FETs. Either a Schottky or a FET will be a dead short. Of course, for such measurements the PSU need to be explicitly unplugged from the wall socket! If all Schottky diodes are good, and you know that you shorted the +12V rail to the +3.3 or the +5V rail, in such cases often the tantalum or small ceramic caps will form a short due to the overvoltage on them (they are rated only up to 6.3V DC).

[@RaduFilip85]

I.ve got shocked several tumes so i.m not so novice. What i.ve done it was to take out whatever was heat sinked and make the sink water cooled by applying a casing on the back..on the front being the field transistors on the switching side respectively the rectifying diodes. inside the casing the water is circulating. connection to the board was done by 2.5 or 1.5 sqmm multifillar coper wire. Still it seemed not to be enough...since the insulation of the wires conecting one of the rectifier diodes S30D45C melted and finaly shorted to the casing. Gues what...it doesn.t work now:) but the big nasty diodes are just fine, no shortage and conducting in right direction.....bottom line i realy need to repair it since the cooling stuff cost me a lot of private time...like this long messagw as well. Btw Thank You for your advices. I.m sure they will ve appreciated world wide by hobists, people who wants to get electrocuted or technicians. Regards.

[@RaduFilip85]

Unde dai si unde crapa ! One out of two D4515 on switching part shorted to base...hopefully that was all...i.ve checked the rest of diodes and transistors and resistors and seems fine...Based on the theory that the most expensive part is subject of failure in a system there should not be something else broken :)

[@DonkeyLearningIT]

If the base of the power transistor have touched some high voltage parts, and the transistor is not driven through a signal transformer, there is a high chance that the PWM controller IC feeding the base have also got hit. In those cases when the power transistor dies, I automatically change the PWM controller if they are easy to order online or from a store. This is because if the PWM controller has issues, the new power transistor will instantly die when you turn the PSU on. On the long run I have figured that replacing the PWM and the transistors works out for me to be cheaper than just replacing the transistors...

[@johnbravo7542]

Donkey Learning IT,thank you so much,for your style of explain the switch mode power supply :-)

[@DonkeyLearningIT]

Thanks for the comment, which has just shown up in my feed after a year! Yeaaay, KZbin comment section is broken as usual ;)

[@ajohpv7033]

Superb sir, great work

[@imtiaznagra8929]

Simply this video is the top of the best list

[@WayniKlaru14344]

Thank you so much Bro !!! I appreciate what you do. Keep it up…!!! God bless..

[@trickedouttech321]

This is a great video. I must say you are doing a fantastic job in your explanations of the Switching mode PSU. However, I have trouble with broken English for the lack of a better term. I could not understand about 10% of your terminologies. However, I must say it is better them most. for some reason as of late, your tube has been flooded with broken English video's. It is very annoying. I end up closing 30-50 videos a week within the first 5 sec when researching a topic just to find a video with an English title that I can understand. NOT IN THIS CASE. Even with the 5-10%, I knew what you meant and your great explanation is what made the difference. you have a talent for education. I appreciated your video and will subscribe as long as you are doing electronics tech videos, KUTGW!

[@DonkeyLearningIT]

First of all thanks for subscribing and for the comment. Which part of the terminology was not clear enough? Based on your comment I would assume that you are native English speaker, and this is why it might bother you if some video is not 100% perfect fluent in English. However, most people do not have the time to spend writing a script or editing the video with voice-over. I have made so far 0$ from my videos, so I cannot spend time on trying to fix everything.

[@tulsidasverenkar3059]

sir, you got very good explaining ,simple basic informative ,thank

[@g00glian0]

So glad I came across your videos!

[@DonkeyLearningIT]

I am also glad that you found the content useful.

[@josephsmith7284]

Really helpful and interesting way of learning. Thanks

[@DonkeyLearningIT]

Thanks for the feedback. Once the whole series is up, it should be even more useful.

[@gordthor5351]

You are an excellent teacher,thanks.

[@DonkeyLearningIT]

Thanks for the comment. Go through the whole list of videos to learn more. Hopefully part 7 will be uploaded this week as well.

[@bestofthebest3821]

do monitors that dont use remote control also have a stand by module /voltage???like a medical signals monitor ? i have 1 that doesnt turn on and the power led doestn lights up either ..

[@mountassirfares3888]

Thank you so much for the lessons and my compliments for you pronouciation, i can get every single word

[@DonkeyLearningIT]

Thanks for watching! Regarding the pronunciation, there is definitely room for improvement. Though, I have to watch native English speaking people from British documentaries with subtitles, so I guess it is all relative...

[@trebel]

good tutorial you got a subscriber Thanks a lot for explanations. Very interesting cheers from Belgium.

[@OldSkoolF]

Love your videos and other channel...

[@spelunkerd]

Brilliant explanations, I'm sub'd. I even kinda like the way you pronounce circuit, ha ha ha.

[@poonlaphsirimala6302]

Easy to understand his word.

[@dadadodo1134]

extra magnifiqe explanation. good work

[@DonkeyLearningIT]

Yeah, I am really happy that you found it "magnifique". After I look at my own videos, they seem to be so bad awful, that often I hesitate to upload them.

[@kitogamichael6416]

Thanks a lot for explanations. Very interesting

[@pa4tsou]

Very helpful video,thank you!

[@DonkeyLearningIT]

Thanks for the comment. Go through all videos, since they are built up as a continuation in a series. I still produce new episodes, only it takes a lot of time to make them.

[@ahmedghamdi3204]

Waiting for part #3 ... thanks

[@peckelhaze6934]

A very good series.

[@AsadAbbas-gz4qr]

You are doing great job

[@pierresbobdoez6588]

Mr donkey you are the best. i which you could talk more on the opto ice, over voltage and current protection etc

[@alioman26]

The best teaching video thanks

[@DonkeyLearningIT]

I wish! Personally I think there are lot better video contents on KZbin, but I try to make a different spin on it, and try to explain things (often even by being boring to some people).

[@patsou6447]

Very good work. Thank you very much!!!

[@DonkeyLearningIT]

Thanks for the feedback.

[@adamsacad8265]

It is very informative video. where is the third video please?

[@DonkeyLearningIT]

I am still working on the third video, it is about 30% done. It will be about inductors in a circuit, magnetic cores, and the basics of chopping transformers.

[@Firas95k]

Absolutely great work, thank you!

[@DonkeyLearningIT]

I am happy that you liked the content. If you got the time, go through the videos in the series to learn more.

[@Vidya1939]

Very NICE TKQ GO ahead next.

[@ryansegodine348]

thank you very much...very informative

[@octapc]

Would a super capacitor be an option for bulk capacitor?

[@DonkeyLearningIT]

Short answer: not really. Reasons are the following: supercapacitors tend to be low voltage devices (up to around 2.5V) due to the electrochemistry of a supercapacitor. Above this voltage the electrolyte will be broken down, so the capacitor will explode. Also, we do not need very large filtering capacitance in SMPS, since the chopping will be done at a high frequency, so that the SMPS controller chip can compensate for small fluctuations. After the fluctuations are reasonably small, increasing the bulk filter capacitor value will just increase wasted power, especially if the inrush current limiting thermistor is not actively bypassed by a relay.

[@DonkeyLearningIT]

Pushed the reply button too early: Third reason why supercaps are no good is that they have a very large leakage current, i.e. they waste too much power.

[@mariopic]

was wondering if i chould get some help i got a crosair hx1050 powersupply that wont turn on basicly its a massive 12v power supply with the 5v and the 3.3v getting steped down from the 12v side found both of them failed so u pulled both rail cards off the pcb and tested the supply it powers on and off i get 10v for a split secont on the 12v rail i also got 5v stand by voltage there was a exploded cap i replaced but got no clue where to look not the supply has pfc as well

[@DonkeyLearningIT]

When you plug it into the mains AC, and you turn on the mains switch, the +5V Stand-by voltage should be always present, not just for a brief moment. Please check this, and make sure first that the +5V stand-by is working properly. I have not fully understood what you meant with the rest. If I got it correctly, you mean that your PSU only has the +12V rail coming from the main chopper transformer (most probably it is a resonant supply), and the +3.3V and +5V rails are being powered with DC-DC converters from this +12V, where each of these DC-DC converters is located on a separate small PCB. Is this correct? In those cases you cannot just remove the DC-DC boards, because the IC which monitors the output voltages will almost instantaneously turn off the PSU if it does not detect +5V and +3.3V at the output. This is most probably what you see. Thus, you will need to repair those DC-DC converter cards. They should be relatively simple. If you can upload high res pictures or a video on KZbin, I can give you some hints what to measure.

[@mariopic]

Donkey Learning IT yes the supply is a massive 12v supply and uses 2 dc to dc converter boards one for 5v the other for 3.3v now when i plug in supply purple wire has 5v the gray wire has 3.5v the green has 3v on them i can upload photos but where do i up load them to

[@mariopic]

also the readings are always present even if i try to ground the green wire and it clicks on and off

[@mariopic]

Donkey Learning IT here is a review of same supply has a take apart photos and inspection www.techpowerup.com/reviews/corsair/hx1050/4.html

[@DonkeyLearningIT]

The pictures are tiny, and one cannot see the two DC-DC boards. Only on one of the pictures one has a glimpse of those boards. In any case, please check the FETs on the DC-DC boards first, and make sure that they are not in shortcircuit. Also, you can feed in +12V DC into the output from an other ATX supply if you have one laying around, and check that they produce the right output voltages of +5V and +3.3V.

[@wilbert61b]

Excellent Course thank you!!

[@DamaKubu]

Nice abstract lesson

[@DonkeyLearningIT]

I tried to present it such that it is not too abstract.

[@shasichennaikumar]

really very good explanation thank you

[@Matthias051]

I am also so impressed of this videos

[@TerryDeSimone]

what is a "Trafo" ?? a Transformer?

[@joeybtv377]

can you provide the schematic diagrams. thank you.

[@ademline2010]

hi, in my SMPS circuit, the input capacitor is showing 315 V and after that the 200 k resistor is going to 10 V to pwm integration. Because of the low voltage, PWM locks itself because it is 10V. Where's your problem? Is it due to resistance?

[@DonkeyLearningIT]

Do you mean that there is a 200K series resistor which is feeding the PWM controller chip? Sorry, I am not fully sure what you meant in your comment.

[@jhliton6755]

Really a good learnig video, waiting for 3rd...

[@pitambersanwal9545]

Thank you for very good explain

[@D1g1tal_H1ppy]

FANTASTIC VIDEOS!

[@technicalexposure9095]

Great teacher.

[@mrm179]

Excellent videos.

[@GroovyVideo2]

Great video - Thank you for making

[@gulfraz3433]

good series. thanks

[@DonkeyLearningIT]

Thanks for watching and commenting!

[@liaustria7790]

good tutoriial you got a subscriber

[@hmvartak]

Nice video. Thanks!

[@batistafrose6009]

Vry good video

[@Guitartime1]

GREAT teacher!!!!!

[@Initial_Gain]

I used to work in this field. Good learning... but why Donkey learning?

[@topmastermind]

thanks! this channel exists!

[@DonkeyLearningIT]

Thanks for the comment. If I would have time to actually produce contents regularly for this channel, that would be awesome.

[@codebitman]

Finally second video :)

[@DonkeyLearningIT]

Yeah, sadly only now. Due to public transport I always get a new flew somehow, almost every 2 months... Third video should be more informative, because we look into the inner life of an inductor in a PFC circuit. It will be fun ;)

[@benwrong6855]

Thank you!

[@Fred_Klingon]

I feel like these second part doesn't contain a lot of new informations.... I will see the next one :)

[@DonkeyLearningIT]

Well, it is really hard to put material together such, that it is not too fast for some people, but it is not too slow for others. Also, if you already know some of the info, it might appear repetitive.

[@nigelclark7360]

Excellent

[@alibakkal2103]

Excellent .

[@DonkeyLearningIT]

Thanks for the excellent comment ;)

[@MrEbhartley]

Really helpful

[@leohobbleohobb3781]

Very good

[@vipulakularathne3664]

good work thank you

[@DonkeyLearningIT]

Keep on watching the other vids in the series as well. It will take about 12 videos to cover the basics of SMPS, but it will be worth it, I am telling ya!

[@ats89117]

Very nice video, but I think at 4:28 you meant to say coma, not enema. These are very different things. Trust me! :-)

[@MrSurath]

thank you so much

[@gedeon1980yt]

well done,

[@viswanathancr2801]

good video

[@DonkeyLearningIT]

Thanks

[@totok_jgn_diganti]

Mr....please add subtitle in Indonesian..thanks

[@yenal5258]

hmmmmmp INPUT................. THANKS A LOT SIR..

[@inone-qk8oo]

Thanks

[@lambertax]

This video is almost the same than the first one. Are you trying to convert plumbers in electronics? Or it's to increase the number of videos for KZbin's algorithm...

[@alfredrein699]

3:08 This Word ist not English? Porschen? I hear it often bud can´t translate

[@ZonaALG]

4:15 shit that scared me out

[@quickfixtechlanka3929]

😀😀❤️🔥🙏

[@carlnikolov]

Sir qweet!

[@steveone]

Circuit s pronounced "Ser kit".

[@danielberei3021]

Steve Smith you have to write him in his languge. Like this " szörkăt "

[@daedaluslv2032]

Cirkuit.

[@richardkaz2336]

Please pronounce circuit as 'circkit'

[@DonkeyLearningIT]

You are the third person who points this out, so I will definitely try to correct it. Donkeys apparently pronounce *cirKUWAIT* or whatever I say on the video, so I need to say *circkit* instead.

[@semedabubakar4907]

haha cirkwit

[@johndro3014]

😆

[@rich1051414]

seerquit

[@clems6989]

How can anyone talk so long and not say anything

[@rsattahip]

You wasted over 4 minutes of nonsense .

[@DonkeyLearningIT]

Sorry for you time, I know how you feel. I guess my videos are not the right material for you.

[@Washburn-rr5eh]

If you can do any better. Then show us your knowledge of electronics and explain to everyone in detail why this video is 4 minutes of wasted nonsense. After watching this 2 part series. I was able to repair my hisense power supply. So to me and probably anyone else watching will have to disagree with your comment.

[@DonkeyLearningIT]

@@Washburn-rr5eh Thanks for the positive comment from your side! However, I have realized that no matter what you do, there is just no way to please everybody. There will be always people who wold have preferred it done differently, harder, faster, stronger...

[@peterduxbury927]

Not one part of this was nonsense. Take a close look at the majority of the replies to his Tutorials. Now ask yourself WHY you fall into the minority???

[@trebel]

good tutorial you got a subscriber Thanks a lot for explanations. Very interesting cheers from Belgium.

[@DonkeyLearningIT]

Thanks for commenting and subscribing. In Belgium do you also have such a warm rainy winter without snow like we got this year here in Austria?

[@paulmorrey733]

Thanks

[@DonkeyLearningIT]

I am glad that you take your time and go through the series!