I've been overly interested in electronics since I turned 9 (12/27/1985), in which I took my sister's Christmas gift Cassette stereo apart lol 😊. I was beat with a hanger but it was well worth it!! At 47, I am still just as curious. I love how you give a drawing. It gives a sense of hands on learning which for me is extremely important. How you explain it all in detail is a huge game changer for me. I wish I known you 20 years ago. Thank you so much for all the time and priceless information you give. I hope you are well and in good health!
Your content is really awesome!!! I can watch your videos for hours on end. Most of my professional working life has been high end (medical, aerospace, etc.... none of this consumer electronics made in China junk) electronics so I had a "high opinion" of myself until I cam across your videos, then I realized I was not as good as I thought I was. You're the kind of bloke who teaches "grand masters" and not "beginners". When you get hours of my attention span you must be good. Imagine that I repaired switch-mode power supplies for a living and I was considered highly competent by my employer, but man I never came close to being the expert you are. Your knowledge is really impressive.
I really appreciate all your videos. I have been doing this professionally over a decade and 2 decades as a hobby. I still learn every day and I would like to thank you for filling in many gaps in my knowledge. Thankyou brother keep it coming please. Peace
Hi Sam, you are not the only one still learning, I am too. In a strange way actually producing these videos is also teaching me more. I guess none of us ever completely master electronics repair, there is always something else to learn.
@@LearnElectronicsRepair Yes brother I totally agree. In fact my work is moving much more in the direction of educating my clients also , sometimes we all learn new things. I have found the best way to approach all things a mystery is with honesty, a good heart and a hell of a lot of trial and error. Some say "failure" I say - well we learnt something so it is never a failure. Certainly learning is my love I just really enjoy the practical side of electronics , soldering and fault finding. As it gets more and more complex - we simply have to stay ahead of the curve but understanding really well fundamental basics go a long long way. Thanks again man, sorry to waffle ! Peace
@@kilbabaplays8944 Both. Mostly Macs but it hasn't always been that way. I am Digithaiz, A1techrepair / Bertscomputerreepairs - been around a while. Not as long as our man here though ! 🙂
This is the 2nd video from your channel i have came across, and im loving the content =) Im a master technician in a car dealership, Your videos will help me save (in time!) a lot of people a lot of money =) Nobody will touch automotive circuitry where im from! keep them coming =) All the best from sunny Scotland
THANK YOU for the amazing and detailed, yet straightforward & simple, walkthroughs and breakdowns. EXTREMELY helpful. I never fixed an ATX PSU before, and after watching a couple videos of yours over the last week, was able to fix it! Such a great feeling😁👍 Keep up the amazing work!!! Its much appreciated.
I just started practicing my soldering and repairing pcbs but i have the utmost respect for components with high voltage like power supplies or anything that is connected to the "mains". Thanks for the helpful information. I really want to try and repair some power supplies too and understanding how they work better definitely helps.
THIS is the place for it!!! Ive watched about 3 full 1-2 hour episodes, half the time while soldering, testing stuff, eating, etc..... and I had bought a faulty power supply less than a week ago, and fix it today. Today was the 2nd real time i actually went to work on it. Anddd.... ITS FIXED! Rectifier wasnt testing right, took it out, replaced with a salvaged br. rectifier from an old CRT tv, double checked the caps & everything, plugged it in, put in the pin to connect Green-to-GND/Blk, and VRMMMmm, fan starts spinning. ahh, SO satisfying, lol.
Congratulations :) Always the best feeling when you plug it in and it works. I'm always afrad it goes BANG when I plug it in for the first time even if everything measured good :D @@delta-KaeBee
Also Bridge rectifier damage I havent seen before :) Usually its caps or mosfets ie. If the bridge rectifier is broken you could also wire one together with 4 diodes :).
😂❤ that accent - yeah? 😂 lol Rather relaxing too. I tend to watch most videos at a faster pace and I’m genetically inclined to repair and build but not good at it. 😂 women ya know? Scrambled. Cheerio!
Tobe honest, I got some tasting of a high voltage from a TV repair many years ago. For a "normal" high voltage of 220V I'm only getting pissed off a little and I might say a few swear words but that's it. The high voltage I got from that TV years ago, I heard some discharge just like a spark sounds, I felt dizzy for a few seconds, gently pulled my hands out of the TV, had to sit down for a while and understood that I am very lucky to still be alive. Never, ever since then I did work on anything recklessly. Every time I took precautionary measures, every time I was working in electronics repair I took extra care, double checked precautionary measures every single time. Never started to work on anything in a rush. It's "safety first" then it comes the working. If I'm tired, I'd rather not work on anything. This routine saved me a lot of trouble for many years. I'm 54 years old now but I might've been already dead at 24. Yes, I remember when it happened for that was the day when I was very close to dying. Don't do what I did. Take safety as the most serious and important thing in your life because it is the most serious and important thing in your life.
Cheers, mate!! I've always wanted to learn electronics and to repair my own stuff. YT and your channel make it possible for me to make my dream come true. Thanks and keep up the good work!!
excellent video. It was very helpful to see a schematic and an explanation of how the circuit worked and current flowed through it. Really helped me to understand how the smps circuit worked and when you know how something works it really helps you to see what's wrong with the circuit.I purchased a couple of ATX nonworking power supplies of eBay to try and diagnose the faults. and thanks to your previous videos I fully understand the dangers involved with capacitors. I also have current limiter which I built from your design and an isolation transformer. thank you so much for the excellent videos, I will let you know if I repaired the two SMPS.
31:53 This the most important part about hot, not safety ground, which you cannot mix with normal ground during measurements. You have to see it. P.s. Thank you again for that. Last time you've explained it to me in comment section, and it flip my repairs knowledge/experience upside down -because I finally understand how measure things on that hot area without making a short or killing my measurement devices.
Definitely that was one of the most important parts of this video. It's great to hear you 'get it' now. It is a big step forward, and it was the same for me back in the day when I finally understood this.
your work is so great i am sure many technicians will agree that it is really golden in the hearts of everyone, a lot of insight.!!! thank you..keep up the great work.
Super helpful video. I have started watching your vids from the start, and have picked up soo much. You have tied a few puzzled together for me, so thanks.
I've been using a screwdriver to discharge caps for over 30 years without any issues... My old man did it as well with big filter caps in old tube amps which is probably where I learned it...
Light bulb (25W is ideal) is also good way to discharge high voltage capacitors. Additional benefit is you can observe bulb to see if caps are discharged.
smps are 4 types, 1 smps isolated, flyback and forward (in the video is a flyback), 3 buck, boost and buck -boost. smps are simple to repair and mod, most of the defective problem come from the "hot side" like 95%, ic controler blow, transistor/mosfet dead or blow, bridge rectifier dead of blow
The main converter in the video is a "half bridge" converter (edit: the first supply looked at tin the video is a half-bridge). A half-bridge requires more complex drive but makes good utilization of the transformer core. True AC is used so the core operates in two quadrants. A forward converter makes quite good use of one quadrant so you get significantly less power through-put than with a half-bridge. A flyback also operates in only one quadrant and relies on energy storage in the main magnetic component and in consequence makes even poorer use of the core. The small stand-by supply is almost certainly a flyback converter. Forward, push-pull and all variants of bridge conveters are buck-derived.
Thank you very much for taking the time to make these videos and for choosing to use some life span to do so. I've got many of these to fix on old computers (just because I want to). I also have some similar supplies in some sub-woofer bass units with internal supplies that have quit and I look forward to using this info to help with those as well. Peace and be well.
Therese videos are incredible pedagogic, even for a mathless beginner, with 4 thumbs, and actually also serves well as an ambient ongoing anti-bore surround therapy. Hot air!
Good evening and very grateful thanks from a recent UK subscriber. Took me a few days a bit at a time to watch the lot but I got there in the end. An amazing tutorial, the ATX PSU thoroughly demystified. Great safety first warnings, I would certainly tackle a duff ATX in the future (can"t make it any worse, right?) but would almost certainly refer back a few times to this vid. I am sure I will become very acquainted with this channel in the future. Once again thanks a lot. I enjoyed this one very much.
Hi Robert, thanks for your comments and it's great to hear you enjoyed the video. Yeah this one got rather long (even by my standards LOL) but like you say, I tried to cover the whole subject and that is not easy and definitely time consuming. If it's any consolation it took me a lot longer to make it than it took you to watch it. 😉 Other than that I would just like to say welcome to the channel, and don't forget to check out the LER discord server Learn Electronics Repair is now on Discord! Come and join the fun, it's free. discord.gg/vam6YC8vwU
Good stuph. Well explained and useful. Somewhere along the line you must have went on a major redux of "uh" and "so" be because I watch an earlier vid of yours that I swear was composed of about 30% of those gap fillers. Well done! So much easier to stay attentive this way.
Good evening. Very long video but...very informative as well! I have really appreciated the theoretically dissertation. Thank you so much Richard. I hope in a part 2 when you will receive the components to finish the excellent job. Regards from Italy. Ah!! Please, if I make any mistake in my English feel free to suggest the correction. This would be perfect to improve my language skills...along with repairing knowledge. Thanks in advance.
Don't worry your English is fine. I wouldn't suggest you perfect your English skills on my attempts to speak it. Apparently I don't speak English very well, despite being born and spending most of my life there LOL 😁
Correct secondary of the main transformer, but that drive transformer should be push pull with split winding on secondary, so one coil per gate-source pair, or base emitter pair. Also, when explaining difference between ground earh and reference ground it is crucial to know why is reference dangerous: every piece of equipment is grounded directly to earth, especially oscilloscope reference ground on the probe(s). So, connecting already earth grounded device to reference ground of power supply makes short of voltage of negative potential to ground=zap (boom). About active PFC: Most new PSUs, no matter the power must have active PFC due to more rigorous regulations on grid power factor. Greater the power factor, less harmonics in the grid and less current draw for the same required power by the load (for example PC, or air conditioner, inverter type, or inverter washing machine etc.). And the boost converter doesn't necessarily need the third bypassing diode. The bypassing diode is for capacitor pre charge, so boosting is in range from 320V DC to around 390V DC on the DC link (on the main capacitors). The second one PSU, with active PFC, considering 2 FETs is most likely two transistor forward topology, so there must be 2 diodes across the winding, and mosfets, that play role of demagnetizing primary winding, in order to maintain volt-second balance for the winding. Hysteresis is part of current mode control, at least for the flyback topology. Want to know details on SMPSs? Go to Keith Billings "Handbook of Switchmode Power Supplies", or similar from Abraham Pressman, then and only then see practical circuits. It just seems like third PSU has synchronous (POWER MOSFETS) rectifiers on the secondaries. Those 2 chokes on the PFC are probably for the interleaved BOOST type topology (2-phase PFC).
I simply love this guy..watfched the vid without blink of an eye .will watch it again so I can understand from 2nd time :) though explanation is more then simple enough to understand.
I have a confession to make, I design PCBs for small electronics, and I really wish I could make a board without vias like these ATX power supplies. I just can't see how they could've done them this way so packed with components wires going everywhere and few or no vias. I'm jealous.
You crack me up with your intro, and have taught me a bunch! I can't help wondering where you're from or where you live. My Australian friend called himself a POME. Maybe you are too! LOL
Yeah I would be a Pommy in Oz, I'm from Stoke-on-Trent in England, where I would be a Potter - but I live and work in Maspalomas, Gran Canaria. I've been living on the island Gran Canaria since November 2016, where I would be an Immigrant (though some British call themselves expats, possibly because they think the Brits are too good to be Immigrants) Actually I consider myself neither Expat or Immigrant, but Nuevo Canarian instead.
What ATX type design do you prefer or think is better in some way? Low esr top quality caps is always mandatory in all the stages? ....your video restore my faith in find good new content creators in this platform, you're excellent teaching what you master. blessings from Chile!
Hello. I am just a beginner on this, I have a question: When is a transformer used, and when a buck regulator or PWM? If my question is stupid, I want to know why. I am really happy with your videos, keep it up!
Ok so A PWM (pulse width modulator) is a component that generates square waves, usually at a set frequency but with a varying duty cycle. By duty cycle I mean the time the square wave is 'on' (a voltage is present) vs the time is is off (no voltage present). It is not a voltage regulator or supply itself, it is simply a source of square waves or pulses of varying width. A buck regulator uses PWM and an inductor coil to generate a (usually stable) lower voltage output from a higher voltage input. It is a DC to DC converter. A SMPS is basically the same thing, in as much has it is a DC to DC converter but it uses a PWM and a transformer to generate the output voltage. The important point is that with a buck regulator there is a physical electrical connection between 'ground' on the input voltage and 'ground' on the output voltage. With an SMPS there is no connection between the 'ground' connections on either side of the transformer. Electrically they both basically do the same job and the electronics would still operate either way. In practice the difference is down to safety for the user of the equipment by isolating them from the high voltage mains supply. Watch the chapter on 'Hot ground vs Safety ground' in this video and if you are still confused let me know and will try to explain it again as this is important to understand if you are going to work on mains powered electronic circuits.
@@LearnElectronicsRepair Ok, got it! I think I was on the right track, but I haven't got the terminology to explain properly. Thank you for clarifying things. Again, appreciate your time spending on guys like me😀
Hello, Ive repaired industrial electronics for over 15 years (inverter drives, PLCs etc for a well known UK company. I was trained using a curve tracer which shows the V/I signature of components and could never imagine only just using a multimeter now as it would be like working blindly. Have you ever used this method?
This great video led me to identify a blown up chip on an ATX supply - it was a seven leg 8 dil with a TYN2 visible and you gave me the info that it was a standby power supply chip probably a TNY209P which I have ordered. Can you suggest where I should look next as to why the chip blew it's top - was it probably from too much current being drawn or do these chips fail like that? Cool video, I enjoyed all 2:13:06 of it and I am a somewhat wiser now. I have 4 ATX PSUs broken at the moment and I'm hoping to salvage at least one of them with your help.
Very good video...sir i have a questions about the pg signal timings ,what are the reasons that this depends on....i have some power supplies with increased timing mother boards fail to start b'cos of this....ur help will be much appreciated....thanks
Heya I love these vlogs for me they may have more detailed info ( I mean wen you drow the main componments I like to see alle the components drown and explanted what they do and how the work ect ect more to learn
41:00 why does it take DC current from the rectifier and turn it into AC current for the secondaries? Is there further rectifiers on the safe side of the board? You mentioned something about avoiding capacitors from filling up or the coil from filling up (inductance?). Don't quite understand that bit, could you go a bit further into that part?
Your secondary side has only 2 power diodes, for 5V and 12V, the 3V3 is generated by the common mode choke that has the 12V and 5V current fed through them, with a mosfet to synchronously rectify the other winding to buck the 5V down to 3V3. Common failures are pretty much always capacitor failure, primary side the small electrolytics that provide base drive to the switching transistors, and the standby supply the electrolytics on the self oscillating side. Then secondary side, where they go open circuit after leaking, and cause high ripple, which results in the power devices being driven so that both turn on at the same time, blowing both short circuit and blowing the bridge rectifier, PFC transistor and diodes, and then bridge rectifier and finally the fuse. Active PFC runs off the standby power supply aux rail, there to operate the small power supply primary, with an optocoupler to turn off the PFC when in standby, so there is lower power use. Passive PFC no need for this, so often the self oscillating supply, providing 9-15VDC to run the 5V regulator providing the standby, and then 9-15V, with a diode feeding in the 12V rail, to run the switching circuit. Running the standby supply is disabled through the feedback to the primary side, and the regulator provides standby power, and when turned off the small oscillator starts up again. 90% of all cheap ATX supplies use the same rough circuit, with variations in them, and easy enough to fix them, though often it is much easier to simply replace the unit, unless you need it to have a specific form factor. Capacitor failure normally first manifests in odd locking up, or reboots, so that can easily be fixed, but semiconductor carnage often is cheaper to repair by replacing it, in it's entirety.
Your secondary side has only 2 power diodes, for 5V and 12V, the 3V3 is generated by the common mode choke that has the 12V and 5V current fed through them, with a mosfet to synchronously rectify the other winding to buck the 5V down to 3V3. ^^^ It could work like that but this depends on the design of the PSU Common failures are pretty much always capacitor failure, primary side the small electrolytics that provide base drive to the switching transistors, and the standby supply the electrolytics on the self oscillating side. Then secondary side, where they go open circuit after leaking, and cause high ripple, which results in the power devices being driven so that both turn on at the same time, blowing both short circuit and blowing the bridge rectifier, PFC transistor and diodes, and then bridge rectifier and finally the fuse. ^^^ Yes agreed. I discuss and test the small capacitors in the base drive circuit during the practical repair example (chapter 11). Bear in mind these capacitors only apply in ATX that has the PWM on the low voltage side and uses a small transformer for the base drive (type 1 as I call them in this video) Active PFC runs off the standby power supply aux rail, there to operate the small power supply primary, with an optocoupler to turn off the PFC when in standby, so there is lower power use. Passive PFC no need for this, so often the self oscillating supply, providing 9-15VDC to run the 5V regulator providing the standby, and then 9-15V, with a diode feeding in the 12V rail, to run the switching circuit. Running the standby supply is disabled through the feedback to the primary side, and the regulator provides standby power, and when turned off the small oscillator starts up again. ^^^ You did watch the video yes? (though I'm not sure how you could as the video is 2hr 15 long and you posted when it had been published less than 1 hour) I ask because I clearly explained all of this (paragraph) of your comment regards how the PFC controller is powered and controlled, and the existence and purpose 9V-15V (sometimes higher 16V - 24V) secondary on the 5V standby supply in two common ATX PSU designs. 90% of all cheap ATX supplies use the same rough circuit, with variations in them, and easy enough to fix them, though often it is much easier to simply replace the unit, unless you need it to have a specific form factor. Capacitor failure normally first manifests in odd locking up, or reboots, so that can easily be fixed, but semiconductor carnage often is cheaper to repair by replacing it, in it's entirety. ^^^^ I'm not sure I would agree with 90% being the half bridge with three transformer design. I see a lot of ATX rated 500W and over, with PFC and PWM controller on the high voltage side (ATX type 2 in the video chapters) and a lot of high power newer ones seem to be the full bridge with synchronous rectification topology (ATX type 3 in the video chapters) The type 4 ATX (single voltage high current SMPS with buck converters) I haven't seen one yet but I bet there are quite a lot of them around these days
This part (@10:00) is quite interesting for me given its possibly the first time I've seen this, but I am a little confused where you were saying we would read 0V if we measured at the full wave rectifier chip given I would of assumed it would of taken the path of going over the diode and then measured the voltage across the capacitor. Thinking about it a bit more I think it comes down to two things, one we have a polarized capacitor that can only discharge its current out from the positive end, which is currently blocked on both sides, to the right of it there is other circuitry that we cannot see but if it was anything that would allow it to discharge, it would of done so already hence it will be some form of a switch, transistor , relay etc that is past that point which is currently turned off therefore blocking the capacitor from discharging. Then to the left of the capacitor is the diode, which again is currently blocking any current flowing. The other part is that in order for a volt meter to work it needs to have some path for electrons to flow through them and I know the design of volt meters requires them ideally to draw no current and just solely read the voltage but in reality there will be some current flowing through them, where really the main thing is that there is a path that electrons can travel through aka no opens in the path. Then there is the fact a volt meter needs is a power supply in order to read voltages, and given our power supply in this case is the polarized capacitor which is actually cut off from the volt meter due to the diode being present, given the volt meter needs to receive this power from the capacitor and is currently being blocked. When we read across the full wave rectifier, the path has an open in it, and therefore we read no voltage. Then when we read from the diode or just directly across the capacitors leads, there is now a path from the positive end of the capacitor through the volt meter and back to the negative end of the capacitor, and despite the current being almost nothing there is a path for the electrons to travel through and therefore we can read the voltage of the capacitor. (I thought I would post this just in case anyone else is stuck, and it can also be checked to make sure its correct but I do think I understand it)
i used to use screwdrivers for high voltage capacitor discharging in power supplies for a long time, until one day i shorted a 400v cap and it took out a big chunk of my screwdriver and it also charred that area of the board very badly and exposed several surrounding traces (it took off the green conformal coating). Its very dangerous, i definitely wont do it anymore. The power resistor looks very nice Im going to try find one in my scrap boards bin.
Hello again. I have another question for you, can you determine the inputs and outputs of the transformer by the markings of the text on the transformers in the ATX-psu's?
You can't. The transformers are custom made for each power supply design. About the only thing you'll find marked on a transformer will be a "house" part number.
This was a super awesome video overall. I especially liked the explanation of hot fround vs safety ground which is critical to understand in order to not blow expensive test equipment! Thank you very much!!
i see also adapters which dont have transformers so what are the benefits of transformers, just safety ? And what are their purpose in system except decreasing voltage to our adjustments? Their switching duty cycle affect current in secondary side or just skin effect make system efficient ?
I have a cheap ATX power supply. it switches on and all the voltages are okay except the 3.3v. The 3.3v on the orange wire is not coming. I check and its not shorted and rectifier diode after the transformer is okay. what can be fault?, did you have this issue before?
I know this is a year old. I was looking for a part 2 for the "practical repair example" at the end but, I don't see it. If you recall, did this PSU get fixed? Did the transistor you had to order along with a new bridge rectifier do the trick or was there any other issues? Just curious. Thanks for the tutorial!
Hi Richard. I have an ATX 600W type I (similar to yours, video 4:00). I want to turn it into DC Bench Supply. Green wire to ground. Violet, brown and gray cables not connected. It works without load. But on 5V rail (14A) a 2 Ω load drops voltage to 4.6V and with 1 Ω it stops. Similar in the other outputs. As you say, I have connected 2 Ω to the brown cable (3.3V) but not solution the problem and it stops... What am I doing wrong? Thanks for everything.
what can I wear to mitigate the danger working with the primary power of the PSU? I got I lot of electrical shocks from power supplies and didn't die yet (that doesn't mean I won't by working with PSU)...
I have 685 watt power supply with active pfc which does not turn on, when i checked the 5vsb output it was about 3 and unstable, can you tell me where to look for the fault ?! i also took out the pfc controller board as if it was the source of problem, but the voltage is still the same, is it from the supervisor chip or is it the optoisolator feedback circuit ? by the way it is the two choke design , and has a controller chip with embedded mosfet for the vsb ... thanx in advance.
Thank you the deep dive into SMPS. I still don't understand how the Standby IC reads the OPTO. Is the IC monitoring the voltage on the transistor side of the OPTO? I know that the transistor in the OPTO can be on more, or on less, depending on the intensity of the LED inside the Optoisolator.
- Standby voltages come in 2 shapes. 1. A switching supply, without feedback but with a linear regulator at the output (in this case the is no opto-coupler), or 2. just a normal switched supply with feedback via an opto-coupler to the primary of the stand-by transformer. If the voltage on the output exceeds the reference of a zener diode or voltage reference, the LED in the opto-coupler will light up more, and the resistance of the photo-transistor will go down. This will lower the on-time on the primary side via a pulse-width modulator circuit (of the standby supply) on the primary side, so the output voltage will go down until it reaches the reference voltage. The photo transistor is actually part of this pulse-width modulation circuit on the primary side. - Now, there can also be other couplers in the schematic that are somehow related to the standby supply. The standby supply supplies power to part of the motherboard. When you press your power button (which is connected to the motherboard) the motherboard will send a signal to the power supply and the standby supply will also power up the PFC and PWM circuit on the primary side. This powering often also goes via an opto-coupler, because you can not directly can not connect your standby power to a circuit on the primary side. Same goes for over-voltage and over-current detection circuits. They are powered by the standby supply, but shut down the primary PWM or PFC via the opto-coupler.
There is most likely a Relay that gets turned on when the Motherboard tells the PSU that you have pressed the power button somewhere on the PC case, then the PSU will get turned off by a /shtdwn signal from the motherboard when the OS has triggered shutdown before exiting it's main loop, I was looking at the PSU AT pinout for the DAA78L Motherboard cannot find the /shtdwn control line is it most likely the power_on# control line.
Hi. Got a PSU that all voltages are fine 3.3V/5V/12V, runs shorting green with black. 300W stated by manufacturer and also says on 12V that can do 13A. I am trying to test it with load as it was pulled from a PC that couldn't make it start, I am using a 12V lamp of 65W (even preheating it with 5V does the same), the 12V drops until it stops due to low voltage (Plan B, so I've bypassed the supervisor IC, pin#4 to ground, same results. I am able to get about 2.5Amps only. Replaced main caps, same, getting 280V, diodes at the input are Ok. Any ideas why isn't able to 12V drops until it stops due to low voltage ?
How to modify an ATX Analyzer to make it actually useful.
ruclips.net/video/yw747J-9F1s/видео.html
Oh man, I love your videos. Great content!
Alors
I've been overly interested in electronics since I turned 9 (12/27/1985), in which I took my sister's Christmas gift Cassette stereo apart lol 😊. I was beat with a hanger but it was well worth it!!
At 47, I am still just as curious. I love how you give a drawing. It gives a sense of hands on learning which for me is extremely important. How you explain it all in detail is a huge game changer for me. I wish I known you 20 years ago. Thank you so much for all the time and priceless information you give. I hope you are well and in good health!
Your content is really awesome!!!
I can watch your videos for hours on end.
Most of my professional working life has been high end (medical, aerospace, etc.... none of this consumer electronics made in China junk) electronics so I had a "high opinion" of myself until I cam across your videos, then I realized I was not as good as I thought I was. You're the kind of bloke who teaches "grand masters" and not "beginners".
When you get hours of my attention span you must be good.
Imagine that I repaired switch-mode power supplies for a living and I was considered highly competent by my employer, but man I never came close to being the expert you are. Your knowledge is really impressive.
I really appreciate all your videos. I have been doing this professionally over a decade and 2 decades as a hobby. I still learn every day and I would like to thank you for filling in many gaps in my knowledge. Thankyou brother keep it coming please. Peace
Hi Sam, you are not the only one still learning, I am too. In a strange way actually producing these videos is also teaching me more. I guess none of us ever completely master electronics repair, there is always something else to learn.
@@LearnElectronicsRepair Yes brother I totally agree. In fact my work is moving much more in the direction of educating my clients also , sometimes we all learn new things. I have found the best way to approach all things a mystery is with honesty, a good heart and a hell of a lot of trial and error. Some say "failure" I say - well we learnt something so it is never a failure. Certainly learning is my love I just really enjoy the practical side of electronics , soldering and fault finding. As it gets more and more complex - we simply have to stay ahead of the curve but understanding really well fundamental basics go a long long way. Thanks again man, sorry to waffle ! Peace
When you say you "do this professionally", do you mean you fix PSUs , or just any stuff with electronics?
@@kilbabaplays8944 Both. Mostly Macs but it hasn't always been that way. I am Digithaiz, A1techrepair / Bertscomputerreepairs - been around a while. Not as long as our man here though ! 🙂
This is the 2nd video from your channel i have came across, and im loving the content =) Im a master technician in a car dealership, Your videos will help me save (in time!) a lot of people a lot of money =) Nobody will touch automotive circuitry where im from! keep them coming =) All the best from sunny Scotland
Thank you, and welcome from sunny Gran Canaria 😁
THANK YOU for the amazing and detailed, yet straightforward & simple, walkthroughs and breakdowns. EXTREMELY helpful. I never fixed an ATX PSU before, and after watching a couple videos of yours over the last week, was able to fix it! Such a great feeling😁👍
Keep up the amazing work!!! Its much appreciated.
I just started practicing my soldering and repairing pcbs but i have the utmost respect for components with high voltage like power supplies or anything that is connected to the "mains".
Thanks for the helpful information. I really want to try and repair some power supplies too and understanding how they work better definitely helps.
THIS is the place for it!!! Ive watched about 3 full 1-2 hour episodes, half the time while soldering, testing stuff, eating, etc..... and I had bought a faulty power supply less than a week ago, and fix it today. Today was the 2nd real time i actually went to work on it. Anddd.... ITS FIXED! Rectifier wasnt testing right, took it out, replaced with a salvaged br. rectifier from an old CRT tv, double checked the caps & everything, plugged it in, put in the pin to connect Green-to-GND/Blk, and VRMMMmm, fan starts spinning. ahh, SO satisfying, lol.
Congratulations :) Always the best feeling when you plug it in and it works. I'm always afrad it goes BANG when I plug it in for the first time even if everything measured good :D @@delta-KaeBee
Also Bridge rectifier damage I havent seen before :) Usually its caps or mosfets ie.
If the bridge rectifier is broken you could also wire one together with 4 diodes :).
The PSU is the best introduction to into the repair Sektor
Thank you, Rich! I ALWAYS learn from you no matter how short or long your videos are. You are very thorough! Cheers!!!
😂❤ that accent - yeah? 😂 lol Rather relaxing too. I tend to watch most videos at a faster pace and I’m genetically inclined to repair and build but not good at it. 😂 women ya know? Scrambled. Cheerio!
excellent video i learned a lot from seeing a hands on visual approach along with schematics.
Tobe honest, I got some tasting of a high voltage from a TV repair many years ago. For a "normal" high voltage of 220V I'm only getting pissed off a little and I might say a few swear words but that's it.
The high voltage I got from that TV years ago, I heard some discharge just like a spark sounds, I felt dizzy for a few seconds, gently pulled my hands out of the TV, had to sit down for a while and understood that I am very lucky to still be alive.
Never, ever since then I did work on anything recklessly.
Every time I took precautionary measures, every time I was working in electronics repair I took extra care, double checked precautionary measures every single time.
Never started to work on anything in a rush. It's "safety first" then it comes the working.
If I'm tired, I'd rather not work on anything.
This routine saved me a lot of trouble for many years.
I'm 54 years old now but I might've been already dead at 24.
Yes, I remember when it happened for that was the day when I was very close to dying.
Don't do what I did.
Take safety as the most serious and important thing in your life because it is the most serious and important thing in your life.
By far the best channel on this topic. Down to earth real life. A lot better than some
Cheers, mate!! I've always wanted to learn electronics and to repair my own stuff. YT and your channel make it possible for me to make my dream come true. Thanks and keep up the good work!!
very detailed analysis, love your videos. I used to do electronic repairs, IT now, but makes me want to go back. Thanks indeed!
this is a super add on to this series :) very in depth on the ATX power supply's :)
excellent video. It was very helpful to see a schematic and an explanation of how the circuit worked and current flowed through it. Really helped me to understand how the smps circuit worked and when you know how something works it really helps you to see what's wrong with the circuit.I purchased a couple of ATX nonworking power supplies of eBay to try and diagnose the faults. and thanks to your previous videos I fully understand the dangers involved with capacitors. I also have current limiter which I built from your design and an isolation transformer. thank you so much for the excellent videos, I will let you know if I repaired the two SMPS.
Please do - it helps everyone here to learn from others who are 'having a go' at fixing stuff.
Did you manage to fix them?
It is good to listen him his voice is certainly a pleasing one to listen to and the way how he explains
Very comprehensive. I definitely learned a lot! Thank you
And that was the intention. It's nice to see it succeed 😄
@@LearnElectronicsRepair the real test for me will be in diagnosing and fixing the 4 or 5 PSUs I have been holding on to in the garage!
31:53 This the most important part about hot, not safety ground, which you cannot mix with normal ground during measurements. You have to see it.
P.s. Thank you again for that. Last time you've explained it to me in comment section, and it flip my repairs knowledge/experience upside down -because I finally understand how measure things on that hot area without making a short or killing my measurement devices.
Definitely that was one of the most important parts of this video. It's great to hear you 'get it' now. It is a big step forward, and it was the same for me back in the day when I finally understood this.
@@LearnElectronicsRepair nm.iip.m n, ko.
First one of your videos that I have watched. Also the first one that I actually come away from understanding what's going on! Great video. Thanks
You're welcome. Maybe you will try a few more. 😉
@@LearnElectronicsRepairwhy do they ground most components
your work is so great i am sure many technicians will agree that it is really golden in the hearts of everyone, a lot of insight.!!! thank you..keep up the great work.
ص، شو اي شو شو شو عم عم
Powerful tutorial that was too short. Thank you.
Haha I'll try to make longer in future 😆
Cool video, with probably enough material for a mini series. I like diodegonewild for power supply youtube videos too.
Super helpful video. I have started watching your vids from the start, and have picked up soo much. You have tied a few puzzled together for me, so thanks.
1:27:56 Hi Richard. We ARE interested! Looking forward for the video of that PSU's repair.
Yes please
I've been using a screwdriver to discharge caps for over 30 years without any issues... My old man did it as well with big filter caps in old tube amps which is probably where I learned it...
What a great video. You are a great Teacher on your knowledge you share . Don’t stop Thanks for taking your time on getting these videos out .
Light bulb (25W is ideal) is also good way to discharge high voltage capacitors. Additional benefit is you can observe bulb to see if caps are discharged.
Yep, that is a good idea 🙂 The light bulb needs to an incandescent or halogen 240V/120V as appropriate and not and LED bulb of course....
I'm using some cheap "discharge pen" from Aliexpress, originally bought for camera flash caps
@@kruno7150 Do you have a link?
smps are 4 types, 1 smps isolated, flyback and forward (in the video is a flyback), 3 buck, boost and buck -boost. smps are simple to repair and mod, most of the defective problem come from the "hot side" like 95%, ic controler blow, transistor/mosfet dead or blow, bridge rectifier dead of blow
The main converter in the video is a "half bridge" converter (edit: the first supply looked at tin the video is a half-bridge). A half-bridge requires more complex drive but makes good utilization of the transformer core. True AC is used so the core operates in two quadrants. A forward converter makes quite good use of one quadrant so you get significantly less power through-put than with a half-bridge. A flyback also operates in only one quadrant and relies on energy storage in the main magnetic component and in consequence makes even poorer use of the core. The small stand-by supply is almost certainly a flyback converter.
Forward, push-pull and all variants of bridge conveters are buck-derived.
King Richard, I find that all of your videos are awesome but this one in particular is your best IMHO
Extrem gut erklärt ! Sehr motivierend mal wieder in die Schrottkiste zu gucken und es selbst zu versuchen. Danke !
Thank you very much for taking the time to make these videos and for choosing to use some life span to do so. I've got many of these to fix on old computers (just because I want to). I also have some similar supplies in some sub-woofer bass units with internal supplies that have quit and I look forward to using this info to help with those as well. Peace and be well.
Thank you so much for your wonderful lectures.
Therese videos are incredible pedagogic, even for a mathless beginner, with 4 thumbs, and actually also serves well as an ambient ongoing anti-bore surround therapy. Hot air!
ty today i fixed my old psu :D , 12 volt schottky diode shorted 1 side
Good evening and very grateful thanks from a recent UK subscriber. Took me a few days a bit at a time to watch the lot but I got there in the end. An amazing tutorial, the ATX PSU thoroughly demystified. Great safety first warnings, I would certainly tackle a duff ATX in the future (can"t make it any worse, right?) but would almost certainly refer back a few times to this vid. I am sure I will become very acquainted with this channel in the future. Once again thanks a lot. I enjoyed this one very much.
Hi Robert, thanks for your comments and it's great to hear you enjoyed the video.
Yeah this one got rather long (even by my standards LOL) but like you say, I tried to cover the whole subject and that is not easy and definitely time consuming. If it's any consolation it took me a lot longer to make it than it took you to watch it. 😉
Other than that I would just like to say welcome to the channel, and don't forget to check out the LER discord server
Learn Electronics Repair is now on Discord! Come and join the fun, it's free.
discord.gg/vam6YC8vwU
Thanks for sharing you knowledge... Greatings from Portugal 🇵🇹 🌟
Good stuph. Well explained and useful. Somewhere along the line you must have went on a major redux of "uh" and "so" be because I watch an earlier vid of yours that I swear was composed of about 30% of those gap fillers. Well done! So much easier to stay attentive this way.
Good evening. Very long video but...very informative as well! I have really appreciated the theoretically dissertation. Thank you so much Richard. I hope in a part 2 when you will receive the components to finish the excellent job. Regards from Italy. Ah!! Please, if I make any mistake in my English feel free to suggest the correction. This would be perfect to improve my language skills...along with repairing knowledge. Thanks in advance.
Don't worry your English is fine. I wouldn't suggest you perfect your English skills on my attempts to speak it. Apparently I don't speak English very well, despite being born and spending most of my life there LOL 😁
Correct secondary of the main transformer, but that drive transformer should be push pull with split winding on secondary, so one coil per gate-source pair, or base emitter pair. Also, when explaining difference between ground earh and reference ground it is crucial to know why is reference dangerous: every piece of equipment is grounded directly to earth, especially oscilloscope reference ground on the probe(s). So, connecting already earth grounded device to reference ground of power supply makes short of voltage of negative potential to ground=zap (boom).
About active PFC: Most new PSUs, no matter the power must have active PFC due to more rigorous regulations on grid power factor. Greater the power factor, less harmonics in the grid and less current draw for the same required power by the load (for example PC, or air conditioner, inverter type, or inverter washing machine etc.).
And the boost converter doesn't necessarily need the third bypassing diode. The bypassing diode is for capacitor pre charge, so boosting is in range from 320V DC to around 390V DC on the DC link (on the main capacitors).
The second one PSU, with active PFC, considering 2 FETs is most likely two transistor forward topology, so there must be 2 diodes across the winding, and mosfets, that play role of demagnetizing primary winding, in order to maintain volt-second balance for the winding.
Hysteresis is part of current mode control, at least for the flyback topology.
Want to know details on SMPSs? Go to Keith Billings "Handbook of Switchmode Power Supplies", or similar from Abraham Pressman, then and only then see practical circuits.
It just seems like third PSU has synchronous (POWER MOSFETS) rectifiers on the secondaries. Those 2 chokes on the PFC are probably for the interleaved BOOST type topology (2-phase PFC).
🤨🧐😋🙃 you lost me. Seems like you maybe taught electrical? 😂😊
I simply love this guy..watfched the vid without blink of an eye .will watch it again so I can understand from 2nd time :) though explanation is more then simple enough to understand.
Excellent 👌 very well explained!!
Excellent Tutorials! Keep Like this!
Thank You
thats the stuff Guvanah
I have a confession to make, I design PCBs for small electronics, and I really wish I could make a board without vias like these ATX power supplies. I just can't see how they could've done them this way so packed with components wires going everywhere and few or no vias. I'm jealous.
You crack me up with your intro, and have taught me a bunch! I can't help wondering where you're from or where you live. My Australian friend called himself a POME. Maybe you are too! LOL
Yeah I would be a Pommy in Oz, I'm from Stoke-on-Trent in England, where I would be a Potter - but I live and work in Maspalomas, Gran Canaria. I've been living on the island Gran Canaria since November 2016, where I would be an Immigrant (though some British call themselves expats, possibly because they think the Brits are too good to be Immigrants) Actually I consider myself neither Expat or Immigrant, but Nuevo Canarian instead.
Aside from the dim bulb tester, what safety equipment do you use, and when? GFCI, isolation transformer, etc. Is your variac isolated?
Very excellent video.
Thank for sharing your knowledge
My pleasure
i do understaning this power supply very well like a piece of cake thing you that you shows the videos
Thank you for the educational infomation your actually managing to teach me lol old dog new tricks kinda thing thanks
Fantastic video!
What ATX type design do you prefer or think is better in some way? Low esr top quality caps is always mandatory in all the stages? ....your video restore my faith in find good new content creators in this platform, you're excellent teaching what you master. blessings from Chile!
Hello.
I am just a beginner on this, I have a question: When is a transformer used, and when a buck regulator or PWM? If my question is stupid, I want to know why. I am really happy with your videos, keep it up!
Ok so
A PWM (pulse width modulator) is a component that generates square waves, usually at a set frequency but with a varying duty cycle. By duty cycle I mean the time the square wave is 'on' (a voltage is present) vs the time is is off (no voltage present). It is not a voltage regulator or supply itself, it is simply a source of square waves or pulses of varying width.
A buck regulator uses PWM and an inductor coil to generate a (usually stable) lower voltage output from a higher voltage input. It is a DC to DC converter.
A SMPS is basically the same thing, in as much has it is a DC to DC converter but it uses a PWM and a transformer to generate the output voltage.
The important point is that with a buck regulator there is a physical electrical connection between 'ground' on the input voltage and 'ground' on the output voltage.
With an SMPS there is no connection between the 'ground' connections on either side of the transformer.
Electrically they both basically do the same job and the electronics would still operate either way.
In practice the difference is down to safety for the user of the equipment by isolating them from the high voltage mains supply.
Watch the chapter on 'Hot ground vs Safety ground' in this video and if you are still confused let me know and will try to explain it again as this is important to understand if you are going to work on mains powered electronic circuits.
@@LearnElectronicsRepair Ok, got it! I think I was on the right track, but I haven't got the terminology to explain properly. Thank you for clarifying things. Again, appreciate your time spending on guys like me😀
Excellent video. Thanks.
You are welcome!
Hello,
Ive repaired industrial electronics for over 15 years (inverter drives, PLCs etc for a well known UK company. I was trained using a curve tracer which shows the V/I signature of components and could never imagine only just using a multimeter now as it would be like working blindly. Have you ever used this method?
Hmm that sounds a bit like 'Huntron Tracker' which I used in the 80s when working for ICL
Excellent, thanks for the video!
This great video led me to identify a blown up chip on an ATX supply - it was a seven leg 8 dil with a TYN2 visible and you gave me the info that it was a standby power supply chip probably a TNY209P which I have ordered. Can you suggest where I should look next as to why the chip blew it's top - was it probably from too much current being drawn or do these chips fail like that? Cool video, I enjoyed all 2:13:06 of it and I am a somewhat wiser now. I have 4 ATX PSUs broken at the moment and I'm hoping to salvage at least one of them with your help.
Really informative video… big thank you
Great video. Thanks!
Very good video...sir i have a questions about the pg signal timings ,what are the reasons that this depends on....i have some power supplies with increased timing mother boards fail to start b'cos of this....ur help will be much appreciated....thanks
Heya I love these vlogs for me they may have more detailed info ( I mean wen you drow the main componments I like to see alle the components drown and explanted what they do and how the work ect ect more to learn
Great vid mate thanks 👍
Thank you very sir 🙏🙏🙏
Well done.
Thank you.
Excellent
Thanks 🙂 This one took quite a lot of work to make.
Very useful thank you
41:00 why does it take DC current from the rectifier and turn it into AC current for the secondaries? Is there further rectifiers on the safe side of the board? You mentioned something about avoiding capacitors from filling up or the coil from filling up (inductance?). Don't quite understand that bit, could you go a bit further into that part?
Your secondary side has only 2 power diodes, for 5V and 12V, the 3V3 is generated by the common mode choke that has the 12V and 5V current fed through them, with a mosfet to synchronously rectify the other winding to buck the 5V down to 3V3.
Common failures are pretty much always capacitor failure, primary side the small electrolytics that provide base drive to the switching transistors, and the standby supply the electrolytics on the self oscillating side. Then secondary side, where they go open circuit after leaking, and cause high ripple, which results in the power devices being driven so that both turn on at the same time, blowing both short circuit and blowing the bridge rectifier, PFC transistor and diodes, and then bridge rectifier and finally the fuse.
Active PFC runs off the standby power supply aux rail, there to operate the small power supply primary, with an optocoupler to turn off the PFC when in standby, so there is lower power use. Passive PFC no need for this, so often the self oscillating supply, providing 9-15VDC to run the 5V regulator providing the standby, and then 9-15V, with a diode feeding in the 12V rail, to run the switching circuit. Running the standby supply is disabled through the feedback to the primary side, and the regulator provides standby power, and when turned off the small oscillator starts up again.
90% of all cheap ATX supplies use the same rough circuit, with variations in them, and easy enough to fix them, though often it is much easier to simply replace the unit, unless you need it to have a specific form factor. Capacitor failure normally first manifests in odd locking up, or reboots, so that can easily be fixed, but semiconductor carnage often is cheaper to repair by replacing it, in it's entirety.
Your secondary side has only 2 power diodes, for 5V and 12V, the 3V3 is generated by the common mode choke that has the 12V and 5V current fed through them, with a mosfet to synchronously rectify the other winding to buck the 5V down to 3V3.
^^^ It could work like that but this depends on the design of the PSU
Common failures are pretty much always capacitor failure, primary side the small electrolytics that provide base drive to the switching transistors, and the standby supply the electrolytics on the self oscillating side. Then secondary side, where they go open circuit after leaking, and cause high ripple, which results in the power devices being driven so that both turn on at the same time, blowing both short circuit and blowing the bridge rectifier, PFC transistor and diodes, and then bridge rectifier and finally the fuse.
^^^ Yes agreed. I discuss and test the small capacitors in the base drive circuit during the practical repair example (chapter 11). Bear in mind these capacitors only apply in ATX that has the PWM on the low voltage side and uses a small transformer for the base drive (type 1 as I call them in this video)
Active PFC runs off the standby power supply aux rail, there to operate the small power supply primary, with an optocoupler to turn off the PFC when in standby, so there is lower power use. Passive PFC no need for this, so often the self oscillating supply, providing 9-15VDC to run the 5V regulator providing the standby, and then 9-15V, with a diode feeding in the 12V rail, to run the switching circuit. Running the standby supply is disabled through the feedback to the primary side, and the regulator provides standby power, and when turned off the small oscillator starts up again.
^^^ You did watch the video yes? (though I'm not sure how you could as the video is 2hr 15 long and you posted when it had been published less than 1 hour) I ask because I clearly explained all of this (paragraph) of your comment regards how the PFC controller is powered and controlled, and the existence and purpose 9V-15V (sometimes higher 16V - 24V) secondary on the 5V standby supply in two common ATX PSU designs.
90% of all cheap ATX supplies use the same rough circuit, with variations in them, and easy enough to fix them, though often it is much easier to simply replace the unit, unless you need it to have a specific form factor. Capacitor failure normally first manifests in odd locking up, or reboots, so that can easily be fixed, but semiconductor carnage often is cheaper to repair by replacing it, in it's entirety.
^^^^ I'm not sure I would agree with 90% being the half bridge with three transformer design. I see a lot of ATX rated 500W and over, with PFC and PWM controller on the high voltage side (ATX type 2 in the video chapters) and a lot of high power newer ones seem to be the full bridge with synchronous rectification topology (ATX type 3 in the video chapters)
The type 4 ATX (single voltage high current SMPS with buck converters) I haven't seen one yet but I bet there are quite a lot of them around these days
This part (@10:00) is quite interesting for me given its possibly the first time I've seen this, but I am a little confused where you were saying we would read 0V if we measured at the full wave rectifier chip given I would of assumed it would of taken the path of going over the diode and then measured the voltage across the capacitor.
Thinking about it a bit more I think it comes down to two things, one we have a polarized capacitor that can only discharge its current out from the positive end, which is currently blocked on both sides, to the right of it there is other circuitry that we cannot see but if it was anything that would allow it to discharge, it would of done so already hence it will be some form of a switch, transistor , relay etc that is past that point which is currently turned off therefore blocking the capacitor from discharging. Then to the left of the capacitor is the diode, which again is currently blocking any current flowing.
The other part is that in order for a volt meter to work it needs to have some path for electrons to flow through them and I know the design of volt meters requires them ideally to draw no current and just solely read the voltage but in reality there will be some current flowing through them, where really the main thing is that there is a path that electrons can travel through aka no opens in the path.
Then there is the fact a volt meter needs is a power supply in order to read voltages, and given our power supply in this case is the polarized capacitor which is actually cut off from the volt meter due to the diode being present, given the volt meter needs to receive this power from the capacitor and is currently being blocked. When we read across the full wave rectifier, the path has an open in it, and therefore we read no voltage.
Then when we read from the diode or just directly across the capacitors leads, there is now a path from the positive end of the capacitor through the volt meter and back to the negative end of the capacitor, and despite the current being almost nothing there is a path for the electrons to travel through and therefore we can read the voltage of the capacitor.
(I thought I would post this just in case anyone else is stuck, and it can also be checked to make sure its correct but I do think I understand it)
i used to use screwdrivers for high voltage capacitor discharging in power supplies for a long time, until one day i shorted a 400v cap and it took out a big chunk of my screwdriver and it also charred that area of the board very badly and exposed several surrounding traces (it took off the green conformal coating). Its very dangerous, i definitely wont do it anymore. The power resistor looks very nice Im going to try find one in my scrap boards bin.
mmm, I still do it till this day but after hearing you story I might think twice next time thank you for life lesson.
@@andrewcastellane7802 it shouldh'v but i got away with it for quite a long time
Great work 👍
Hello again.
I have another question for you, can you determine the inputs and outputs of the transformer by the markings of the text on the transformers in the ATX-psu's?
You can't. The transformers are custom made for each power supply design. About the only thing you'll find marked on a transformer will be a "house" part number.
Thumbs up done sir tnx for the video tutorial presentation
This was a super awesome video overall. I especially liked the explanation of hot fround vs safety ground which is critical to understand in order to not blow expensive test equipment! Thank you very much!!
Let's try to use denoiser VST on your vocal path during film editing ;)
i see also adapters which dont have transformers so what are the benefits of transformers, just safety ? And what are their purpose in system except decreasing voltage to our adjustments? Their switching duty cycle affect current in secondary side or just skin effect make system efficient ?
Do you know what would be a cool video idea for building a simple SIMP PSU with spare PSU parts!
I would have enjoyed to se it working in the end
I have a cheap ATX power supply. it switches on and all the voltages are okay except the 3.3v. The 3.3v on the orange wire is not coming. I check and its not shorted and rectifier diode after the transformer is okay. what can be fault?, did you have this issue before?
Very nice videos. Do You remember in what video You are working with A cBel ? I've got one, PC7033, which is not working at all. Dead in other word.
Question here, what can cause on an ATX power supply, for it to power the 20+4 pin connector but not the CPU 4+4 connector?
Thanks a lot...
I know this is a year old. I was looking for a part 2 for the "practical repair example" at the end but, I don't see it. If you recall, did this PSU get fixed? Did the transistor you had to order along with a new bridge rectifier do the trick or was there any other issues? Just curious. Thanks for the tutorial!
Really best ever .
WoW!! 😃
All good - as usual 🙂
Cheers!
Hi Richard. I have an ATX 600W type I (similar to yours, video 4:00). I want to turn it into DC Bench Supply. Green wire to ground. Violet, brown and gray cables not connected. It works without load. But on 5V rail (14A) a 2 Ω load drops voltage to 4.6V and with 1 Ω it stops. Similar in the other outputs. As you say, I have connected 2 Ω to the brown cable (3.3V) but not solution the problem and it stops... What am I doing wrong?
Thanks for everything.
what can I wear to mitigate the danger working with the primary power of the PSU? I got I lot of electrical shocks from power supplies and didn't die yet (that doesn't mean I won't by working with PSU)...
I have 685 watt power supply with active pfc which does not turn on, when i checked the 5vsb output it was about 3 and unstable, can you tell me where to look for the fault ?! i also took out the pfc controller board as if it was the source of problem, but the voltage is still the same, is it from the supervisor chip or is it the optoisolator feedback circuit ? by the way it is the two choke design , and has a controller chip with embedded mosfet for the vsb ... thanx in advance.
Where did you get rectified UK mains as being 270V? pk =rms x root2 i.e. 240Vrms -> 339Vpk when I went to college.
If there is a pfc circuit the voltage gets increased again.
@@kriswillems5661That may well be so, but that doesn't address my comment, does it?
This. I was wondering exactly same, there seems to be error, isn't there?
Hey Rick. What name of tools to connect the psu cable to the main when you wanna measure/test the psu with your multimeter?
I mean when female plug of the cable has been removed
This will be fun. 👍🇮🇪💚
what's the make of that multimeter? the make is blurred on the video
Thousands of thumbs up
Thank you so much.
Thank you the deep dive into SMPS. I still don't understand how the Standby IC reads the OPTO. Is the IC monitoring the voltage on the transistor side of the OPTO? I know that the transistor in the OPTO can be on more, or on less, depending on the intensity of the LED inside the Optoisolator.
OK let me think about it and make a short (I promise) but detailed 😉video on this topic
- Standby voltages come in 2 shapes. 1. A switching supply, without feedback but with a linear regulator at the output (in this case the is no opto-coupler), or 2. just a normal switched supply with feedback via an opto-coupler to the primary of the stand-by transformer. If the voltage on the output exceeds the reference of a zener diode or voltage reference, the LED in the opto-coupler will light up more, and the resistance of the photo-transistor will go down. This will lower the on-time on the primary side via a pulse-width modulator circuit (of the standby supply) on the primary side, so the output voltage will go down until it reaches the reference voltage. The photo transistor is actually part of this pulse-width modulation circuit on the primary side. - Now, there can also be other couplers in the schematic that are somehow related to the standby supply. The standby supply supplies power to part of the motherboard. When you press your power button (which is connected to the motherboard) the motherboard will send a signal to the power supply and the standby supply will also power up the PFC and PWM circuit on the primary side. This powering often also goes via an opto-coupler, because you can not directly can not connect your standby power to a circuit on the primary side. Same goes for over-voltage and over-current detection circuits. They are powered by the standby supply, but shut down the primary PWM or PFC via the opto-coupler.
There is most likely a Relay that gets turned on when the Motherboard tells the PSU that you have pressed the power button somewhere on the PC case, then the PSU will get turned off by a /shtdwn signal from the motherboard when the OS has triggered shutdown before exiting it's main loop, I was looking at the PSU AT pinout for the DAA78L Motherboard cannot find the /shtdwn control line is it most likely the power_on# control line.
Hi. Got a PSU that all voltages are fine 3.3V/5V/12V, runs shorting green with black. 300W stated by manufacturer and also says on 12V that can do 13A. I am trying to test it with load as it was pulled from a PC that couldn't make it start, I am using a 12V lamp of 65W (even preheating it with 5V does the same), the 12V drops until it stops due to low voltage (Plan B, so I've bypassed the supervisor IC, pin#4 to ground, same results. I am able to get about 2.5Amps only. Replaced main caps, same, getting 280V, diodes at the input are Ok. Any ideas why isn't able to 12V drops until it stops due to low voltage ?
20K subs in the blink of an eye
It looks that way 😊
Why not connect safety ground on the low voltage side to earth ground coming in through the third AC connector prong?