How to repair a switching "switch mode" power supply. See what's involved. Also a brief explanation about the difference between Linear and switch mode power supplies.
You started out with a SMPS made by Power Systems, Inc. I was the Product Safety Engineer for PSI for nearly 30 Years. I think the model shown was in the series of late PS-1600's or PS-1700's. Enjoyed watching that work again! LOVED that company and my old job! I traveled all over the world for them. BTW; that green module in the primary has a saw tooth generator and a low voltage dc reference voltage that slides up and down across the saw tooth. thereby tell the switcher to stay on for a longer or shorter period of time based on the load conditions, as felt thru the feedback loop from the sec to primary using that opto you spoke about. Wow, I am retired and its been over 10 yrs since I left America. (retired in Philippines) PSI went out of business about 8 years before that! So, the memories are wonderful! Also, the reason we used the RTV between all the caps was to add ruggedness to the supply. We used a HALT test chamber and a random vibration test at the same time we took temps up and down to find the failure points. We brought them up to about 140C before they failed, then down to -60C before they failed and found that most of our supplies lived at 30G's but would fail by 60G's. I ran that area. My people monitored about 30-50 components during the test for temperature and we monitored the input and output voltages on each channel. I also ran the RFI/EMI Testing and got them approved thru UL/CSA/TUV, etc. (I believe the standards that one met was UL/CSA60950) and often made sure they would pass the conducted and radiated emissions testing also to ISO Standards. I also sat on two technical committees in Canada helping to write the International Safety Standards for the IT industry. Later, I worked for the German TUV Agency as a Product Test Engineer. LOVED my work!
Absolutely the finest teaching around. You have a gift, I wish my instructors would have had even 50 percent of your ability to transfer knowledge in such seamless way. Best on youtube for sure. Thank You!
@Jeremy Mettler eh, there's something about teaching that you can't really buy. There's some merit to your point, but at the same time the big-salad-earning folk... while probably great at what they do, they're not necessarily also great at teaching. There's a number of vital components that have to be there to make a good teacher. That's why it's a rare breed. Be that as it may, we're still underappreciating the average teacher. The lot of us just want to be taught, but they can't do all the work for us. We have to learn... to learn.
+Mr Carlson's Lab Mathematically, switching power supplies are very complex to understand. I don't think type 2 and 3 compensation feedback is easy to understand.
I never attempted to try and understand the engineering of of SMPS and for me it was enough that I could comprehend them enough to effect repairs to high replacement cost OEM units that made sense to repair like your TEK supply. I cut my teeth on IBM PC supplies back in the 80's to learn about SMPS technology.
When replacing polarized parts which are not marked (I.E. caps), the easiest way to identify the negative is to put your meter on continuity and put one probe on (chassis) ground and the other on each pin of where the cap goes until you get a beep.
If I need to replace a through-hole IC, my preferred method is to cut the pins as close to the IC body as possible in order to leave as much of each individual pin in the board as I can, then I simply go round and remove the remains of each pin with tweezers and my iron. Then remove the solder with wick. Using this method lessens the chances of damaging the PCB significantly, it's also a lot easier and faster.
Ah the good ole SMPS the most common failure in modern junk! I spend hours working out faults on that kind of crap. Televisions are notorious for SMPS failures, crusty caps and short circuit diodes being the most common failures, but they can go right down to the darn right obscure and hard to find component failures that make you question the real meaning of life! (But hey, you get a warm feeling when you find the fault or touch the 400v LOL). Keep up the good work, good clear explanations and gripping videos. 5*
If I haven't said this before I'll say it again.. you are a quality teacher. Some people honestly don't have the ability to teach no matter how much training they receive but you have the natural ability. Please keep up the good work!
@ANDREWAUSFA hi mate Just wanted to say, i have not seen the PYE logo since i was a kid thanks for the memory i had a PYE Tv later i had a Rank Arena hehe
yeah! Mr Carlson is the ultimate sen-say.. And his Kung Fu is strong!!!! what i really love about him is he never say's a fix is impossible.. the man's a real gem!!!
Watching these SMPS videos reminds me of my time working at a power supply manufacturers. Testing units from the production line to working with design engineers building their prototypes and developing them to production status. One challenging job I had was developing a 30kV pulse supply to be used on a magnetron. I wasn't privileged enough to know what the final product was (secret stuff). Another excellent video Mr C. and I've watched quite a few of them so far.
Yeah, back in the 1970's we cut them off at the chip-case, then pull the pins off the board 1 at a time...solder sucker....then you got nice place for the new ones......I worked on a lot of TTL back then.....those 7400 series, ran hot and failed often....a gate goes bad...change the whole chip..
One more important comment, to regulate the output voltage, the control circuit senses the output current and increases the conduction time of the switching transistor to regulate the voltage. Love your work!!
Paul, great video! I've been servicing SW mode PSs for many years and have found anomalies that don't make any sense and today was one of those days. Working for a college that has very limited budgets, I have taken it upon myself to repair as many electronic items as possible. The majority of these failed devices are due to a bad SW PS. With a few exceptions, all they needed were new electrolytic caps, and most of the time it is a small 10µf to 47µf cap near the control/regulator chip that needs to be replaced, although, I usually also replace the filter caps at the output for good measure. Anyway, the sole purpose of that small cap seems to be one of obsolescence, or a timer cap. When it starts to lose its capacitance, the output amperage starts to drop and when enough capacitance is lost, the PS may make a ticking noise due to the PS starting and stopping on a continual basis, even with no load. Now for the weird part... I pulled the "timer" cap from this no-name PS (20V @ 2A) since it was "ticking" on and off at about 2 Hz, and my cap tester showed it was well within tolerance of the 47µf value. Normally, this B&K, model 830, cap meter has always showed a greatly diminished value but not this time. I replaced the cap anyway and the PS came back up to full voltage and power output. I then analyzed the bad cap using a sensitive analog VOM and both the old and the new cap exhibited the same readings for charging time and leakage, so I'm at a complete loss as to why the PS circuit likes the new cap but not the old one. And this is not the first time this has happened. The only possibility I can think of is that breakdown is occurring in the cap, such as its leakage is exceedingly high at its rated voltage and causing a shut down. So I put the bad cap on my lab PS and set it to 20 V, and the leakage current reading is 0.2 µA. Then ran the same test with a new cap and it had a current leakage of 1.0 µA, five times higher than the old cap. So, if the leakage current goes to low, these PS's shut down? Could this get any weirder? If you have any insight or info about this anomaly I'd appreciate hearing from you. Thank you.
If I might add a little bit in here, the problem might be that the ESR of the capacitor had greatly increased. The capacitor with increased ESR might test just fine at higher frequencies, but this cap needs to filter and hold up the voltage to the regulator @ 120Hz and if the ESR is too high and the capacitor Xc' diminishes in relation to the ESR. I had it happen before on guitar amplifiers that I've repaired. I check the filter caps and they show within 5% of correct value @ 1KHz or higher, but when I check it at 100Hz it registers anywhere between 40 - 60% low. Replace the caps and Bob's your uncle. Again, this is just something I've experienced in the past, so I thought I would pass it along
The best investment I ever made was buying a hakko desoldering gun. Man that made my life so much easier. I can't believe I was throwing away PCB's because I couldn't be bothered with desoldering when it is so much easier with a desoldering gun. You don't have to get an expensive one like hakko either, I just like to buy tools to last.
Very good explanation of the switch mode power supply, especially with your diagram you drew. If not already, you would make an excellent electronics professor. You have a very good teaching method.
Mr Carlson's Lab I am no electronics expert by a long shot. I have learned so much from UA-cam. I had an old friend several years ago that you remind me of. He could fix anything electronic. If any of the area cities electronics repair shops could not figure out a problem, they would bring it to Jack. I think he really enjoyed them bringing him stuff they couldn't fix! Almost always, next thing you know, the apparatus was working again. You sir are so very talented, and it is a pleasure to watch you work, even if it is above my head. Thanks for the videos.
Absolutely fascinating; the world of electronics and the way YOU present it to us. You are an inspiration at best. Thank you so much. I feel pepped up and positive. Good luck and much love. Cheers! 😊👍
Man, you're so gifted. I ve worked all my life with engineers, and they either specialize in analog, and look at digital like Alice in Wonderland, or specialize in RF and ignore everything else, or specialize in industrial controllers and when they see a tube amp, well, ... Alice again, and so on. But you are knowledgeable about everything. You should be in the Army Corps of Engineers. Or NASA. At the very least Elon Musk might want to speak with you. Oh, yeah, but you might earn less than you do now.
David W. Berning used a clever form of efficient but quiet scheme for voltage regulation in that he used an R/F frequent oscillator into a transformer and achieved regulation by varying the frequency of the oscillation. His objective was complete absence of switching noise such that an am radio could be placed next to the power supply that not a trace of interference noise can be detected or heard! This power supply design was or is being used in his auto preamp and amplifier design.
Mr Carelson...did you Test the IC's after Removal? Did you Test the Removed Capacitors? Would like to know what Component/s was causing the Unit not Operate.
Sometimes an old SMPS will stop running because the sum of all little faults ie. leaking capacitors. I wouldn't turn it on without a new driver IC otherwise you risk blowing up the output MOSFETs. Just good practice.
Worth mentioning a current limiting mains supply can be improvised by using an incandescent lamp in series with the supply. A 150watt mains tungsten or halogen lamp will do. If it lights up brightly you know the power supply is shorted and can disconnect the supply. Another useful side effect of this is that the lamp will flash indicating the working of an active PFC circuit where present. Still you definitely want an isolation transformer if your testing power supplies on the bench.
@Ritesh Kakkar if you mean the point at which it starts conducing in reverse then attach it in reverse to a regulated bench power supply at say 100mA current and increase the voltage until amps increase and the constant current light comes on, that's the reverse bias voltage
@Ritesh Kakkar I think mostly they are used in reverse, to make sure if the voltage reaches a certain limit (the breakdown voltage), it can shunt the current somewhere else, like a sort of voltage regulator. You get 3.3v, 4.5v, 5v, 9v etc up to 24v I think. In reality if you be a 5 volt regulator it's more accurate to use a chip like the LM7805
@Ritesh Kakkar Zener diode: cheap, works well at low current (which is all the uC will need, makes circuit way less complex. The resistor on its Anode further helps to limit the current it has to dissipate.
Your shop brings back memories of my father's shop when I was a little boy. My father was an sound engineer for the RCA corporation. Repairing sound systems all across NYC it was great fun being in the projector booths and seeing racks of AMPS in the winter you never needed heat the equipment provided it. My dad passed away just as the transistor came on the market every thing was tube operated. I miss his great wealth of know how from radio and tv repair which I saw from a very young age. He started his repair business in 1918 when he was 14 in his fathers basement. I became an electrical contractor installing alarm systems and generators building my own controls as much was not commercially available. Customers learned very quickly never say to me it can't be done I always proved them wrong. Much to there dismay and amazement. Today every one in my field is an expert or certified my father would have called them tube pullers putting wheels on miscarriages. Artificial stupidity is what I am waiting for.
I learned a lot about switch board power supplies for your video. (I'm attempting to repair a power supply for an ASIC bitcoin mining machine.). Extremely helpful! Thanks!
Best electronics teaching channel I found hands down. I've been repairing electronic devices nearly 40 years full time and there is always something new to learn!! Thank you. 😉
Hi! Could you consider to make a video about how to observe the noise caused by SMPS, and how to filter them? I think it should be interesting and useful for many people. THX
Excellent video on switch mode PS. I'm definitely not at your level of expertise......but curious as to why you still insist on using those old oscilloscopes, instead of the newer digital types??
Hi Paul, Couple of suggestions that might make it easier to remove the components from the board without damaging the traces or PCB. 1. If you are just replacing an IC then cut the legs off the IC before attempting to desolder the pins that way you only need to remove 1 pin at a time. It also means that you can grab the loose pin from the IC side whilst touching the solder side with the iron and gently pull the pin out. It really leaves a very clean hole that way. 2. When applying heat to the joint try and not press the iron into the board. I.E. try and float the iron on the molten solder. That way there is no physical force transferred directly onto the board. As you are no doubt aware the traces are bonded to the board and that bonding comes loose when you apply heat. If you can minimise any physical force during this time then the traces should stay in place and not get damaged. Regards, Graeme
I did a (UK) ONC in electronics back in the early 90's. (I subsequently moved onto computing.) I wish my electronics lecturers and tutors had been as good and as easy to follow as Mr C. (One lecturer however did say that the then current syllabus took the fun out of electronics.) Regarding SWPS some even caused problems with certain computers at one time and it was not unknown to resolve by moving onto another make of power supply. I would have thought bench variable power supplies are best if of linear type to get over the RF issue as you don't always know what you will be testing, though many do use variable SMPS for this.
Totally a nice video with specific reference to the leaky capacitors replacements the care need to be exercised. Thank you Sir and hope that more like this might be posted in the days ahead.
Thanks so much for a well scripted film.If it's not scripted,you have an incredible sense of what to show us.I'm working on a Behringer PMP1680s Europower powered mixer that just blinks the leds on the front panel.I'll now be able to check some of the SMPS, key components. Thanks again!
"Tittally""...I haven't heard that one before :) You mention the one of the greatest tips that I figured out years ago for component removal/replacement...apply fresh solder to any joint to facilitate easy and much quicker part removal, hence, less heat to a possibly fragile board. Also, on an IC that I'm removing and not going to reuse, I recommend snipping the legs off of the body of the IC and then removing the legs one by one. Once they're out, use a small stick-pin and apply the solder tip to the hole to melt the solder and push the stick-pin through the hole to clean it. This process saves a lot of solder wick and/or solder-sucking on most repairs and saves the consumables for the most difficult situations that need those tools. Cheers Paul, Dan G.
Paul, what criteria did you consider when replacing caps? Voltage and Farad are obvious but what about temperature ripple and impedance when installed into the circuit.
To Mr. Carlson, another great instructional video. I took some electronics class's years ago but forgot a lot of it over the years but the way that you explain things makes even complicated things look less complicated. Thanks for doing a great job helping people to understand electronics. Cheers!
Commenting to watch this later. Working on some power supplies as a student for UMN smallsat. We have a power supply for some external testing that we bought which is of the switching variety. Edit: Man this video is fantastic.
Bravo Paul. Thank you very much for sharing these awesome videos with us. I do appreciate the time and effort you put in to each and everyone. All my best. Bobby
When soldering a number of multi lead components I tend to solder one leg of the first component, then move onto the next component and solder just one pin of that and so on. That way each component has a chance to cool off before it is revisited by the solderibng iron
Perhaps worth pointing out that when testing diode or transistor junctions with a multi meter, some meters (particularly the older analogue types) have the positive of their internal battery connected to the BLACK lead of the probe. So there is a possibility of deeming a good device bad.
Speaking of getting shocked, managed to touch 3 400v caps at the same time yesterday. Nice little pick me up after a long day :P wasn't my finest hour.
Great demonstration Paul; switch mode supply are very efficient, the only downside is they need about 90 volts to start making variable increase very tricky and in some cases blow the power supply when it pulls to much current. As I recall the switch mode operates within +-1% making regulation very tight.
@@MrCarlsonsLab you certainly know your electronics backwards. Respect... I am just a retired bench and field tech. Used to do business equipment. How I fell on that vat of poo escapes me. I like how you know valves, even all the weird tricks they used in the 1930s. And you are totally cool with modern gear as well, including SMPS supplies. You certainly fix and mod a wide range of gear! But.... I've done a lot of digital, conversion and RADAR as well as my passion, hi fi audio.
Can a lithium ion smart battery charger be powered by a switching power suply? I have an AC 220v to DC 36v 34A sps, used it with the Isdt t8 battery charger at 20A and although barely warm, after some burned smell, I heard a pop and it stopped delivering voltage, still hear the relay switching on, fan working, but no dc voltage.
As always you are the best one in the explanation, very simple and full of information i am really understanding the difference between smps and linear power supply and does it work big thanks
+Robert Langford LOL, "Standing up" surface mount technology on a vertical board, interfaced to through hole components on the main board. How did I Do?? :^)
Thank you Sir again! it is my first day enjoying your electronic videos they are really useful, it is hard for me to get out of my computer because I am really learning a lot from you. Thank God that gave you that intelligent and that understanding of the energy that He created.
Hello there...quick question...I have a JBL PRX718xlf powered subwoofer model and its having an amplifier problem.....what its doing as when I power the unit up the subwoofer was making like a pop crackling weird type noises...as I disconnect the input from the unit I can hear a slight humming sounds with a little bit of crackling and when I put a input signal to it the sub the sub sounded very low on power and very distorted sounding and when I power the unit off I can hear like a thump sounds thru the sub as well too...I have no idea of why the sub is acting in a strange way and I had it for 2 years and never have any problems with it....and the next day as I took the amplifier out of the box from the sub and tested the sub with another amplifier it work fine with no problem and I knew that there is something wrong with the amplifier itself...Im assuming its the power supply problem going on within the amplifier itself and I have no clue of how to fix it.....I got a video loading up now soon if you like to see it on my channel about the problem.....I just wanna know what should I do.....Thanks.
This guy's lab it unbelievable. He does a GREAT job explaining things. Like switch mode power supplies. I watch his videos all the time. Thanks for taking the time to be so descriptive.
The first answer I got from a tech. College teacher when I asked why not stick to the type PSU was SMPS was far more efficient unlke the preferred linear supply which wastes power.
In a 7y old PSU (coolermaster V750) which I bought cheap - how long before I should be worried about failing of capacitors (bulk is Nichicon 105C 560mF/450V) ? Should I messure the ripple current with oscilloscope to determine if ripple is too high under load ? Using 350W load (my card and processor draw 350W tops) and no coil whine is present under load (if that can be seen as a good indication of properly filtered voltage)
I noticed that you didn’t show how you connected the mains supply on this. Did you include the little, “pre-power” supply board from the Tektronix’s cabinet? If not, did you connect the “safety ground” AND the neutral, or just the neutral? I have pesky TDS 420A whose power supply won’t fire up completely; it only gives half voltages. I’ll recap it but I need to know how to hook it up afterwards. I didn’t include the safety ground in the initial test because the common and safety are connected in the circuit breaker box. I wonder if the power supply needs BOTH connected to run properly when tested we ithout the “pre-supply” board
when i was a bench tech back in the mid 80's when I removed a bad dip I just got a small pair of clippers and cut all the legs on the dip package then removed the dip package then the legs one by one...really saves the circuit traces.
My SMPS from a TDS420A scope has a completely different board. It is double sided (not single sided) but it looks fairly similar component-wise. I’ll try to add a photo of it, but I’m not very good at UA-cam. Thoughts?
Carlson, you are really a good teacher! I learnt lot of electronics theory and trouble shooting skill from your video. Your speaking was so clear and very understandable, even to me a non-English speaker. Thank you very much!
HI, excellent video, i have watched it many times and as luck would have it, i recently picked up a TDS 460 for cheap and someone messed with the power supply. They didnt replace the caps, so i will do this, but they also disconnected LF1 (which i assume is for protection?) and they removed SP1 and shorted E4 and E12 together. Any idea what the value of SP1 would be? It sits between E11 and E12...
Sir Carlson I want to bypass the main power of SMPS because the bridge type diode is shorted and I have no replacement can I tap DC after 1 diode rectifier in circuit please help me.
The best explanation on how SMPS works with an in-depth explanation of where these are unsuitable and/or what additional devices are needed for these when running sensitive audiovisual equipment.
I've got a programmable led sign that is not powering on. I opened it up and found a smps built by mean well. I tested the output pins and found no voltage whatsoever. I removed the smps and opened it up, expecting to find an obvious parts failure but all the components look to be fine. I would like some help on diagnosing and repairing this part if you are interested please let me know. The output of the supply is 5volts 20amps. I don't have a bench top power supply setup yet and all of the power bricks I have aren't capable of doing 20 amps at 5 volts. I do have an old PC power supply that I can setup to do bench testing with but I have not spent the time to do so because I have been preoccupied with another project involving firmware extraction, which is a very exciting and eye-opening task in it self. Sorry for rambling, I really look forward to hearing from you. Thanks in advance.
A transistor with a C_E short will test still, as two diodes. Also, this is a simple test, you have no idea of the transistor actually works.. Only that the junction looks OK. I would remove it and use a transistor tester, just be be sure. I have had electrolytics in SMPSU's dry out and look like 50pF instead of 200uF, say. I hate SMPSU's as they rarely fail gracefully......
No offence here professor Carlson but … Need closer views of the broken trace. (zoom in with camera) No low melt solder used. (less heat on components or copper traces) No flux used. (easy to transfer solder) No trace protection. (protect trace and not get corroded) Was the transistor leg re-solder. Thanks for understanding.
You started out with a SMPS made by Power Systems, Inc. I was the Product Safety Engineer for PSI for nearly 30 Years. I think the model shown was in the series of late PS-1600's or PS-1700's. Enjoyed watching that work again! LOVED that company and my old job! I traveled all over the world for them. BTW; that green module in the primary has a saw tooth generator and a low voltage dc reference voltage that slides up and down across the saw tooth. thereby tell the switcher to stay on for a longer or shorter period of time based on the load conditions, as felt thru the feedback loop from the sec to primary using that opto you spoke about. Wow, I am retired and its been over 10 yrs since I left America. (retired in Philippines) PSI went out of business about 8 years before that! So, the memories are wonderful! Also, the reason we used the RTV between all the caps was to add ruggedness to the supply. We used a HALT test chamber and a random vibration test at the same time we took temps up and down to find the failure points. We brought them up to about 140C before they failed, then down to -60C before they failed and found that most of our supplies lived at 30G's but would fail by 60G's. I ran that area. My people monitored about 30-50 components during the test for temperature and we monitored the input and output voltages on each channel. I also ran the RFI/EMI Testing and got them approved thru UL/CSA/TUV, etc. (I believe the standards that one met was UL/CSA60950) and often made sure they would pass the conducted and radiated emissions testing also to ISO Standards. I also sat on two technical committees in Canada helping to write the International Safety Standards for the IT industry. Later, I worked for the German TUV Agency as a Product Test Engineer. LOVED my work!
Thanks for taking the time to write Charles!
It shows that you really did like your job. Dave.
@@1903A3shooter Thx Dave.
Amazing story
Electronics. Mankind’s savior. Love it.
Absolutely the finest teaching around. You have a gift, I wish my instructors would have had even 50 percent of your ability to transfer knowledge in such seamless way. Best on youtube for sure. Thank You!
+orange70383
Thanks for the kind words!
@Jeremy Mettler eh, there's something about teaching that you can't really buy. There's some merit to your point, but at the same time the big-salad-earning folk... while probably great at what they do, they're not necessarily also great at teaching.
There's a number of vital components that have to be there to make a good teacher. That's why it's a rare breed.
Be that as it may, we're still underappreciating the average teacher. The lot of us just want to be taught, but they can't do all the work for us. We have to learn... to learn.
@Jeremy Mettler That's ridiculous and quite childish.
Excellent video as always, great information and you make it easy to understand.
+RadioHamGuy
Thanks!
+Mr Carlson's Lab Mathematically, switching power supplies are very complex to understand. I don't think type 2 and 3 compensation feedback is easy to understand.
RadioHamGuy i concurr! 2 thumbs up to this channel!
I never attempted to try and understand the engineering of of SMPS and for me it was enough that I could comprehend them enough to effect repairs to high replacement cost OEM units that made sense to repair like your TEK supply. I cut my teeth on IBM PC supplies back in the 80's to learn about SMPS technology.
When replacing polarized parts which are not marked (I.E. caps), the easiest way to identify the negative is to put your meter on continuity and put one probe on (chassis) ground and the other on each pin of where the cap goes until you get a beep.
If I need to replace a through-hole IC, my preferred method is to cut the pins as close to the IC body as possible in order to leave as much of each individual pin in the board as I can, then I simply go round and remove the remains of each pin with tweezers and my iron. Then remove the solder with wick. Using this method lessens the chances of damaging the PCB significantly, it's also a lot easier and faster.
A known good method for removal , destroy the chip of course so don't pull a good chip..
Mike Hawkins same!
oop's it wasn't that chip o well . On some tight plate through holes it's easier to do that then damaging the pcb
Ah the good ole SMPS the most common failure in modern junk! I spend hours working out faults on that kind of crap. Televisions are notorious for SMPS failures, crusty caps and short circuit diodes being the most common failures, but they can go right down to the darn right obscure and hard to find component failures that make you question the real meaning of life! (But hey, you get a warm feeling when you find the fault or touch the 400v LOL).
Keep up the good work, good clear explanations and gripping videos. 5*
If I haven't said this before I'll say it again.. you are a quality teacher. Some people honestly don't have the ability to teach no matter how much training they receive but you have the natural ability. Please keep up the good work!
As usual the best teacher on UA-cam, thank you.
Excellent video as always. Thanks for your time making it, which I'm sure will be appreciated by lots of viewers.
+Andrewausfa
Thanks for the kind comment Andrew!
@ANDREWAUSFA
hi mate
Just wanted to say, i have not seen the PYE logo since i was a kid
thanks for the memory
i had a PYE Tv
later i had a Rank Arena hehe
my brain after watching this: " *I Know Kung Fu* "
yeah! Mr Carlson is the ultimate sen-say.. And his Kung Fu is strong!!!!
what i really love about him is he never say's a fix is impossible.. the man's a real gem!!!
Mr. Carlson could say "All I'm offering is the truth."
It’s just amazing how knowledgeable and unflappable you are, I don’t think there is anything you would not be able to design or repair. Respect
"Bad things happen.. Really bad things" cracked me up lol. Nothing wrong with some magic smoke if done on purpose. ;)
Watching these SMPS videos reminds me of my time working at a power supply manufacturers. Testing units from the production line to working with design engineers building their prototypes and developing them to production status. One challenging job I had was developing a 30kV pulse supply to be used on a magnetron. I wasn't privileged enough to know what the final product was (secret stuff). Another excellent video Mr C. and I've watched quite a few of them so far.
When removing a sus IC just cut it out from the top.
Less heat stress on the copper tracks.
Yeah, back in the 1970's we cut them off at the chip-case, then pull the pins off the board 1 at a time...solder sucker....then you got nice place for the new ones......I worked on a lot of TTL back then.....those 7400 series, ran hot and failed often....a gate goes bad...change the whole chip..
this comment aged like wine
One more important comment, to regulate the output voltage, the control circuit senses the output current and increases the conduction time of the switching transistor to regulate the voltage. Love your work!!
The theory part showing the switching vs linear supply was excellent! I get the feeling a 10x more difficult repair would still be nothing for you.
Scope rebuild?
Yes, please!
I'd love to see you (re-)building a scope, especially if it's a Tek.
+Thilo Niewoehner
Me Too! (stay tuned:^)
Tek's never need re-building....
great video!!! I did not know about the LM723 chip, cool little regulator chip. thanks mike
Paul, great video! I've been servicing SW mode PSs for many years and have found anomalies that don't make any sense and today was one of those days. Working for a college that has very limited budgets, I have taken it upon myself to repair as many electronic items as possible. The majority of these failed devices are due to a bad SW PS. With a few exceptions, all they needed were new electrolytic caps, and most of the time it is a small 10µf to 47µf cap near the control/regulator chip that needs to be replaced, although, I usually also replace the filter caps at the output for good measure.
Anyway, the sole purpose of that small cap seems to be one of obsolescence, or a timer cap. When it starts to lose its capacitance, the output amperage starts to drop and when enough capacitance is lost, the PS may make a ticking noise due to the PS starting and stopping on a continual basis, even with no load.
Now for the weird part... I pulled the "timer" cap from this no-name PS (20V @ 2A) since it was "ticking" on and off at about 2 Hz, and my cap tester showed it was well within tolerance of the 47µf value. Normally, this B&K, model 830, cap meter has always showed a greatly diminished value but not this time. I replaced the cap anyway and the PS came back up to full voltage and power output. I then analyzed the bad cap using a sensitive analog VOM and both the old and the new cap exhibited the same readings for charging time and leakage, so I'm at a complete loss as to why the PS circuit likes the new cap but not the old one. And this is not the first time this has happened.
The only possibility I can think of is that breakdown is occurring in the cap, such as its leakage is exceedingly high at its rated voltage and causing a shut down. So I put the bad cap on my lab PS and set it to 20 V, and the leakage current reading is 0.2 µA. Then ran the same test with a new cap and it had a current leakage of 1.0 µA, five times higher than the old cap. So, if the leakage current goes to low, these PS's shut down? Could this get any weirder?
If you have any insight or info about this anomaly I'd appreciate hearing from you. Thank you.
If I might add a little bit in here, the problem might be that the ESR of the capacitor had greatly increased. The capacitor with increased ESR might test just fine at higher frequencies, but this cap needs to filter and hold up the voltage to the regulator @ 120Hz and if the ESR is too high and the capacitor Xc' diminishes in relation to the ESR.
I had it happen before on guitar amplifiers that I've repaired. I check the filter caps and they show within 5% of correct value @ 1KHz or higher, but when I check it at 100Hz it registers anywhere between 40 - 60% low. Replace the caps and Bob's your uncle.
Again, this is just something I've experienced in the past, so I thought I would pass it along
@@KeyboardsJR Thank you for that bit if info, could explain the effect I've been experiencing. Much obliged!
The best investment I ever made was buying a hakko desoldering gun. Man that made my life so much easier. I can't believe I was throwing away PCB's because I couldn't be bothered with desoldering when it is so much easier with a desoldering gun. You don't have to get an expensive one like hakko either, I just like to buy tools to last.
Very good explanation of the switch mode power supply, especially with your diagram you drew. If not already, you would make an excellent electronics professor. You have a very good teaching method.
Thanks Tom!
Mr Carlson's Lab I am no electronics expert by a long shot. I have learned so much from UA-cam. I had an old friend several years ago that you remind me of. He could fix anything electronic. If any of the area cities electronics repair shops could not figure out a problem, they would bring it to Jack. I think he really enjoyed them bringing him stuff they couldn't fix! Almost always, next thing you know, the apparatus was working again. You sir are so very talented, and it is a pleasure to watch you work, even if it is above my head. Thanks for the videos.
I agree he really blows me away. Talk about a natural.
Absolutely fascinating; the world of electronics and the way YOU present it to us. You are an inspiration at best. Thank you so much. I feel pepped up and positive. Good luck and much love. Cheers! 😊👍
This is the best tutorial about SMPS on utube..thumbs up indeed.
Man, you're so gifted.
I ve worked all my life with engineers, and they either specialize in analog, and look at digital like Alice in Wonderland, or specialize in RF and ignore everything else, or specialize in industrial controllers and when they see a tube amp, well, ... Alice again, and so on.
But you are knowledgeable about everything. You should be in the Army Corps of Engineers. Or NASA. At the very least Elon Musk might want to speak with you.
Oh, yeah, but you might earn less than you do now.
I love this. I was an engineer in the UK repairing Hammond Organs for many years. Retired now, but still repair things just for fun.
David W. Berning used a clever form of efficient but quiet scheme for voltage regulation in that he used an R/F frequent oscillator into a transformer and achieved regulation by varying the frequency of the oscillation. His objective was complete absence of switching noise such that an am radio could be placed next to the power supply that not a trace of interference noise can be detected or heard! This power supply design was or is being used in his auto preamp and amplifier design.
When replacing ic's always put a socket there.
Desoldering - in industry we used to clip the pins off the chips, then heat & tweeze them off. Then suck off the solder.
Mr Carelson...did you Test the IC's after Removal? Did you Test the Removed Capacitors? Would like to know what Component/s was causing the Unit not Operate.
Sometimes an old SMPS will stop running because the sum of all little faults ie. leaking capacitors. I wouldn't turn it on without a new driver IC otherwise you risk blowing up the output MOSFETs. Just good practice.
@@Fjohre ..Yeah....those pesky capacitors need to get out, and why not just replace those 2 IC's...what, a $ or each...
Worth mentioning a current limiting mains supply can be improvised by using an incandescent lamp in series with the supply. A 150watt mains tungsten or halogen lamp will do. If it lights up brightly you know the power supply is shorted and can disconnect the supply. Another useful side effect of this is that the lamp will flash indicating the working of an active PFC circuit where present. Still you definitely want an isolation transformer if your testing power supplies on the bench.
Thanks for another great video Paul! You're a spectacular teacher. Greetings from Arizona.
+Thema inproblem
Thanks for your kind comment!
That makes two greetings from the cactus patch
A capacitor is not bad. It is just misunderstood. Why did the transistor see a psychiatrist? Because it was bipolar.
Frank
WHAT! Single puny diode rectifier on the output? You need a FUUUULLL BRIDDGEEE RECTIFIEEER for high power applications. Mehdi will be mad!
@Ritesh Kakkar if you mean the point at which it starts conducing in reverse then attach it in reverse to a regulated bench power supply at say 100mA current and increase the voltage until amps increase and the constant current light comes on, that's the reverse bias voltage
@Ritesh Kakkar I think mostly they are used in reverse, to make sure if the voltage reaches a certain limit (the breakdown voltage), it can shunt the current somewhere else, like a sort of voltage regulator. You get 3.3v, 4.5v, 5v, 9v etc up to 24v I think. In reality if you be a 5 volt regulator it's more accurate to use a chip like the LM7805
@Ritesh Kakkar Zener diode: cheap, works well at low current (which is all the uC will need, makes circuit way less complex. The resistor on its Anode further helps to limit the current it has to dissipate.
Your shop brings back memories of my father's shop when I was a little boy. My father was an sound engineer for the RCA corporation. Repairing sound systems all across NYC it was great fun being in the projector booths and seeing racks of AMPS in the winter you never needed heat the equipment provided it. My dad passed away just as the transistor came on the market every thing was tube operated. I miss his great wealth of know how from radio and tv repair which I saw from a very young age. He started his repair business in 1918 when he was 14 in his fathers basement. I became an electrical contractor installing alarm systems and generators building my own controls as much was not commercially available. Customers learned very quickly never say to me it can't be done I always proved them wrong. Much to there dismay and amazement. Today every one in my field is an expert or certified my father would have called them tube pullers putting wheels on miscarriages. Artificial stupidity is what I am waiting for.
How the "F" can anyone dislike this video?
Beats the heck out of me. Paul is among the best electronics teachers on You Tube
I learned a lot about switch board power supplies for your video. (I'm attempting to repair a power supply for an ASIC bitcoin mining machine.). Extremely helpful! Thanks!
Glad I could help!
Man, you are the Legend. I've learned a lot. Thanks
You partially look like Arnold Schwarzenegger
Best electronics teaching channel I found hands down. I've been repairing electronic devices nearly 40 years full time and there is always something new to learn!! Thank you. 😉
Hi! Could you consider to make a video about how to observe the noise caused by SMPS, and how to filter them? I think it should be interesting and useful for many people. THX
Again, A+..................
What if it doesn't start after re-cap + IC's ?
Hi Paul, great explanation and rebuild / refurbishment of the SMPS. The mystic falls around SMPS technique :^) Take care 73
+TRXBench
Thanks Peter :^)
Excellent video on switch mode PS. I'm definitely not at your level of expertise......but curious as to why you still insist
on using those old oscilloscopes, instead of the newer digital types??
Hi Ralf. I still prefer the low noise, and the options that all the plugins give me. They both have their place though.
It would be an interesting challenge to reassemble the oscilloscope and could be a fun video!
+Rogerio Lazzari Jr
It sure would! (stay tuned :^)
Hi Paul,
Couple of suggestions that might make it easier to remove the components from the board without damaging the traces or PCB.
1. If you are just replacing an IC then cut the legs off the IC before attempting to desolder the pins that way you only need to remove 1 pin at a time. It also means that you can grab the loose pin from the IC side whilst touching the solder side with the iron and gently pull the pin out. It really leaves a very clean hole that way.
2. When applying heat to the joint try and not press the iron into the board. I.E. try and float the iron on the molten solder. That way there is no physical force transferred directly onto the board. As you are no doubt aware the traces are bonded to the board and that bonding comes loose when you apply heat. If you can minimise any physical force during this time then the traces should stay in place and not get damaged.
Regards,
Graeme
Oops just noticed Mike Hawkins stated virtually the same comment :-) I really should read the comments before posting :-)
Great video can't wait to see the oscilloscope repair :-)
I did a (UK) ONC in electronics back in the early 90's. (I subsequently moved onto computing.) I wish my electronics lecturers and tutors had been as good and as easy to follow as Mr C. (One lecturer however did say that the then current syllabus took the fun out of electronics.) Regarding SWPS some even caused problems with certain computers at one time and it was not unknown to resolve by moving onto another make of power supply. I would have thought bench variable power supplies are best if of linear type to get over the RF issue as you don't always know what you will be testing, though many do use variable SMPS for this.
nice work Mr C. thanks
+MreViewer
Thanks!
You are doing a great job , Sir Just love your videos. Keep up with the good job.
Well explained, I was impressed with the way he removed the ic, and it's so nice to hear him say soldering and not soddering! That drives me mad.
The correct pronunciation in North American English is SOD-er. Check a dictionary if you don't believe me.
Totally a nice video with specific reference to the leaky capacitors replacements the care need to be exercised. Thank you Sir and hope that more like this might be posted in the days ahead.
Glad you enjoyed Joseph!
I never get tired of that shot in the beginning. It looks like you're in a rocket ship or space shuttle.
Thanks so much for a well scripted film.If it's not scripted,you have an incredible sense of what to show us.I'm working on a Behringer PMP1680s Europower powered mixer that just blinks the leds on the front panel.I'll now be able to check some of the SMPS, key components. Thanks again!
"Tittally""...I haven't heard that one before :) You mention the one of the greatest tips that I figured out years ago for component removal/replacement...apply fresh solder to any joint to facilitate easy and much quicker part removal, hence, less heat to a possibly fragile board. Also, on an IC that I'm removing and not going to reuse, I recommend snipping the legs off of the body of the IC and then removing the legs one by one. Once they're out, use a small stick-pin and apply the solder tip to the hole to melt the solder and push the stick-pin through the hole to clean it. This process saves a lot of solder wick and/or solder-sucking on most repairs and saves the consumables for the most difficult situations that need those tools. Cheers Paul, Dan G.
Paul, what criteria did you consider when replacing caps? Voltage and Farad are obvious but what about temperature ripple and impedance when installed into the circuit.
To Mr. Carlson, another great instructional video. I took some electronics class's years ago but forgot a lot of it over the years but the way that you explain things makes even complicated things look less complicated. Thanks for doing a great job helping people to understand electronics. Cheers!
You're Welcome Dennis!
Commenting to watch this later. Working on some power supplies as a student for UMN smallsat. We have a power supply for some external testing that we bought which is of the switching variety. Edit: Man this video is fantastic.
Bravo Paul. Thank you very much for sharing these awesome videos with us. I do appreciate the time and effort you put in to each and everyone.
All my best.
Bobby
+Bobby Tectalabyss
Thanks Bobby! Guy's like you make it worth it!
When soldering a number of multi lead components I tend to solder one leg of the first component, then move onto the next component and solder just one pin of that and so on. That way each component has a chance to cool off before it is revisited by the solderibng iron
Perhaps worth pointing out that when testing diode or transistor junctions with a multi meter, some meters (particularly the older analogue types) have the positive of their internal battery connected to the BLACK lead of the probe. So there is a possibility of deeming a good device bad.
thanks ❤ sir you teaching very well I am from India and I am engeneering student
Thanks and welcome!
Amazingly awsome simple description of a smps. Ty.
You're welcome!
Speaking of getting shocked, managed to touch 3 400v caps at the same time yesterday. Nice little pick me up after a long day :P wasn't my finest hour.
Great demonstration Paul; switch mode supply are very efficient, the only downside is they need about 90 volts to start making variable increase very tricky and in some cases blow the power supply when it pulls to much current. As I recall the switch mode operates within +-1% making regulation very tight.
Great video, as usual.
Glad you enjoyed it!
@@MrCarlsonsLab you certainly know your electronics backwards. Respect...
I am just a retired bench and field tech. Used to do business equipment. How I fell on that vat of poo escapes me.
I like how you know valves, even all the weird tricks they used in the 1930s. And you are totally cool with modern gear as well, including SMPS supplies. You certainly fix and mod a wide range of gear!
But....
I've done a lot of digital, conversion and RADAR as well as my passion, hi fi audio.
May I have questions.?
Why in smps psu transformer use a solid ferid core instead metal plate ( like ordinary transformer).?
Look up: "transformer core permeability" Also look up: "reluctance."
@@MrCarlsonsLab thank you..
Can a lithium ion smart battery charger be powered by a switching power suply? I have an AC 220v to DC 36v 34A sps, used it with the Isdt t8 battery charger at 20A and although barely warm, after some burned smell, I heard a pop and it stopped delivering voltage, still hear the relay switching on, fan working, but no dc voltage.
As always you are the best one in the explanation, very simple and full of information i am really understanding the difference between smps and linear power supply and does it work big thanks
Please explain "hybrid", to me it means a cross between two biologicaly diferent varieties or species.
+Robert Langford
LOL, "Standing up" surface mount technology on a vertical board, interfaced to through hole components on the main board. How did I Do?? :^)
Thank you Sir again! it is my first day enjoying your electronic videos they are really useful,
it is hard for me to get out of my computer because I am really learning a lot from you.
Thank God that gave you that intelligent and that understanding of the energy that He created.
You are the smartest guy on UA-cam.
Nice test gear in there👍
Brilliant. Not that I'm too interested in electronics, but your talent and the way you can talk about complex things in a simple way, I just love.
57 people discharged the filter caps through their finger.
so the switching supply runs at 100hz china are they less efficient on or 50/60 hz system
Hello there...quick question...I have a JBL PRX718xlf powered subwoofer model and its having an amplifier problem.....what its doing as when I power the unit up the subwoofer was making like a pop crackling weird type noises...as I disconnect the input from the unit I can hear a slight humming sounds with a little bit of crackling and when I put a input signal to it the sub the sub sounded very low on power and very distorted sounding and when I power the unit off I can hear like a thump sounds thru the sub as well too...I have no idea of why the sub is acting in a strange way and I had it for 2 years and never have any problems with it....and the next day as I took the amplifier out of the box from the sub and tested the sub with another amplifier it work fine with no problem and I knew that there is something wrong with the amplifier itself...Im assuming its the power supply problem going on within the amplifier itself and I have no clue of how to fix it.....I got a video loading up now soon if you like to see it on my channel about the problem.....I just wanna know what should I do.....Thanks.
This guy's lab it unbelievable. He does a GREAT job explaining things. Like switch mode power supplies.
I watch his videos all the time. Thanks for taking the time to be so descriptive.
The first answer I got from a tech. College teacher when I asked why not stick to the type PSU was SMPS was far more efficient unlke the preferred linear supply which wastes power.
In a 7y old PSU (coolermaster V750) which I bought cheap - how long before I should be worried about failing of capacitors (bulk is Nichicon 105C 560mF/450V) ? Should I messure the ripple current with oscilloscope to determine if ripple is too high under load ? Using 350W load (my card and processor draw 350W tops) and no coil whine is present under load (if that can be seen as a good indication of properly filtered voltage)
I noticed that you didn’t show how you connected the mains supply on this. Did you include the little, “pre-power” supply board from the Tektronix’s cabinet? If not, did you connect the “safety ground” AND the neutral, or just the neutral? I have pesky TDS 420A whose power supply won’t fire up completely; it only gives half voltages. I’ll recap it but I need to know how to hook it up afterwards. I didn’t include the safety ground in the initial test because the common and safety are connected in the circuit breaker box. I wonder if the power supply needs BOTH connected to run properly when tested we ithout the “pre-supply” board
when i was a bench tech back in the mid 80's when I removed a bad dip I just got a small pair of clippers and cut all the legs on the dip package then removed the dip package then the legs one by one...really saves the circuit traces.
My SMPS from a TDS420A scope has a completely different board. It is double sided (not single sided) but it looks fairly similar component-wise. I’ll try to add a photo of it, but I’m not very good at UA-cam. Thoughts?
You're an amazing teacher. I want to be your student
Always inspiring to see a state-of-the-art repair methods and decisions. thanks Paul!
Carlson, you are really a good teacher! I learnt lot of electronics theory and trouble shooting skill from your video. Your speaking was so clear and very understandable, even to me a non-English speaker. Thank you very much!
Glad you enjoyed Mr. Lee!
HI, excellent video, i have watched it many times and as luck would have it, i recently picked up a TDS 460 for cheap and someone messed with the power supply. They didnt replace the caps, so i will do this, but they also disconnected LF1 (which i assume is for protection?) and they removed SP1 and shorted E4 and E12 together.
Any idea what the value of SP1 would be? It sits between E11 and E12...
Sir Carlson I want to bypass the main power of SMPS because the bridge type diode is shorted and I have no replacement can I tap DC after 1 diode rectifier in circuit please help me.
So..... Look for/replace burned up stuff, fix bad soldering/lands and shotgun replace (most) all the capacitors....?
Pretty much.
I am blessed ! my GOD bless you and your children with his grace
The best explanation on how SMPS works with an in-depth explanation of where these are unsuitable and/or what additional devices are needed for these when running sensitive audiovisual equipment.
Thanks for the tutorial vids. Your explanations are easy to understand.
محاضره جميله جدا
شكرا لك
لماذا لم يصنع محول و به مخارج 12 و 5 و 3 فولت
ما الفرق
I've got a programmable led sign that is not powering on. I opened it up and found a smps built by mean well. I tested the output pins and found no voltage whatsoever. I removed the smps and opened it up, expecting to find an obvious parts failure but all the components look to be fine. I would like some help on diagnosing and repairing this part if you are interested please let me know. The output of the supply is 5volts 20amps. I don't have a bench top power supply setup yet and all of the power bricks I have aren't capable of doing 20 amps at 5 volts. I do have an old PC power supply that I can setup to do bench testing with but I have not spent the time to do so because I have been preoccupied with another project involving firmware extraction, which is a very exciting and eye-opening task in it self. Sorry for rambling, I really look forward to hearing from you. Thanks in advance.
Hi
I have an ATX power supply
It only shows 5v standby
Is there any way to get rid of standby circuit ?
By connecting a jumber?😅
Excellent video, you are werry easy to understand and i like your viedos a lott
Thanks Andre!
A transistor with a C_E short will test still, as two diodes.
Also, this is a simple test, you have no idea of the transistor actually works.. Only that the junction looks OK.
I would remove it and use a transistor tester, just be be sure.
I have had electrolytics in SMPSU's dry out and look like 50pF instead of 200uF, say.
I hate SMPSU's as they rarely fail gracefully......
No offence here professor Carlson but …
Need closer views of the broken trace. (zoom in with camera)
No low melt solder used. (less heat on components or copper traces)
No flux used. (easy to transfer solder)
No trace protection. (protect trace and not get corroded)
Was the transistor leg re-solder.
Thanks for understanding.
Iam looking at buying a cheap tek 420 oscilloscope that doesn't power up, will it be the PSU that is the problem I wonder ?
How does the switching power supply get away with using a half-wave rectifier on the output side?