Super detailed and very educational. I was trained as an EE many years ago but have not practiced as one for over 20 years but I’m jumping back in now as a hobby and it’s great to get a refresher on basic principles like you offer here. Keep up the except work!
Hi Peter. So glad that you are back making electronic education and repair videos. I really appreciate that you started at the mains and went through as much checking as possible without removing the board from the chassis. Also really like that you showed us the different types of switching power supplies and how they work. I know that you could have just checked some different test points and located the faulty regulator, but that would not of helped all of us that had no knowledge of how switching power supplies worked. Thank you again. John C
Linear power supplies are my specialty when I was a tech. I'm 72 now and just cannot see as well as when I was younger. I understand linear supplies better than switching supplies. I have found that failing diodes are the most common failure in linear supplies. Of course I only have 120 volts AC to deal with here in the US. Very seldom do you have to replace a failed capacitor. I've also seen burnt resistors in the circuits. You can make most repairs with a good multi-meter. W Rusty Lane K9POW in eastern Tennessee
Peter is back with a gold mine! The tech who goes inside the heart of smps circuits. Show them electrons moving around. By the way, you got one of the best handheld multimeters on your bench. At the top on the same level as the Flukes.
It's weird. RU-vid won't let me edit my posts. It keeps returning an error. What's up RU-vid??? The full wave bridge rectifiers (diodes) usually go first. You are starting at the right spot. Incoming voltages have to be correct, diodes must be okay, then voltage regulators must be checked. I don't think I've ever seen a power transformer burned out. It's usually some little pesky resistor burned up. I worked on an old RCA TV set my father-in-law gave me. It was a nice TV at the time--back in the mid 70's. He tried to get it fixed locally and no one could fix it. So he gave it to me. I first plugged it in and gave it a smoke test and sure enough there was a resistor in the audio circuit that was smoking. I didn't have a schematic for it so I just guessed at the resistor value and inserted a 1K ohm resistor and the TV came back to life. Another problem developed. We had wooden floors and when you walked across the floor near the TV it would flash on and off. So I pulled the board with the with the IF section containing the video amp and found a solder ball rolling around shorting out the video transistor. Dumped out the solder ball and we used that TV for over 25 years. It finally developed a high voltage leak, so I sealed it up with some silicone. Finally it developed a high voltage leak that I couldn't fix. It got junked then. W Rusty Lane K9POW in eastern Tennessee
Brilliant diagnostic work! I have a SMPS that operates my disabled wifes reclining chair that she sits and sleeps in. The original PSU failed recently failed so I bought her a cheap Chinese replacement replacement but I would like to repair the original unit. You have given me many avenues to try and fix it. Many thanks Lynton G4XCQ
I ran a Motorola Communications Business for 26 years, and watching you work with all the high tech equipment, makes me think of the thousands of dollars I could have made if I had excess to such at the time.
Thank you TRX! This was a beautiful video, rich with helpful content and tips, not only on fixing this SMPS, but so much more, so well explained. Congratulations on a video well done!
Great! Id like to see you repair Professional military hf receivers like Hagenuk, R&S, Racal etc! I'm very happy that you come back again here ! Danke! Ciao ! 73
Well done! At times a little over-explained for my tastes, but necessary for a good teacher. I enjoy your voice and your accent. You voice reminds me of training engineers years ago from Krautkramer back when we would get training on a new instrument.
@@TRXLab I think you need to keep doing it the way you are. I find you are very thorough. I get frustrated also when videos are too short - lol. I would rather have them long.
another great video. Going to use some of your techniques on the jetstream power supply i am working. It is looking like the problem is in the controller board. When I get some more time I will work on it. Keeping the videos coming.
I do not know how I missed this tutorial. Out in January for me to only come across it in September. This tutorial is fucken too good, hammering the points home practically as well as theoratically. I wish you can do one on VFD's. Thank you very much.
Great video. I like the way you took us through your systematic troubleshooting method. I don't know if you noticed this or not, but it seemed like the ground pin (center pin?) on the voltage regulator had what appears in the video the first time that you showed it from underneath, a cracked solder joint all the way around. If my eyes are working properly that could have very well been the cause of the regulator not passing any voltage. If you noticed it and reflowed the solder then of course the replacement was necessary. Again, great video. thanks for sharing.
Finally I found time to watch this 🙂, totally agree with you: SMPS can seriously destroy your day if you don't treat them with respect. Love the Polo shirt buddy, it's a great colour.
Great explanation! I somethimes fix SMPS powe rsuply, but my experience on that isn't good as your. I was rarely lucky like that, there was in most of cases, Mosfet blown up, and also the IC oscillator ( or its circuit) with troubles. Somethimes there was also issues on feedback control circuits. Often, of course Capacitors... specially those ones in the secondary side that are specific for hig frequency switching, with low ESR that, if too much aged, cannot do their Job as well. I love the way as you explain all the job! it is a good way to teach, theory adding practical measuremet and how to do measurements in safe and right way. I saw also a usefull instrument to make safe the measurements with oscilloscope (Micsig DP10013), in future i will buy one same as your. You have plenty of nice instruments... that Sencore LC77 is really amazing. Thank you for all the explanations... i will follow you to learn more. I would also contact you if possible to ask you something about your R&S CMT 54 .
Good day Sir Thank you very much for the informative video. I always understood that using an isolation transformer between the mains and the device under test, causes its output to not be mains earth referenced anymore(floating) and thus allows you to connect earthed equipment, like an oscilloscope, to any part of the power supply without fear of damage. So when you do connect the ground crocodile clip of the standard probe, which is connected to mains earth, to any point in the circuit, that point then becomes earth referenced. I do agree that a differential probe is the safest. Pity it is so expensive.
Fantastic video. Please keep up the circuit analysis diagnosis explanation type video with schematics. You’re a really great teacher, it’s obvious that you put a lot of effort into this. Thank you very much.
Nice job love your explainations to detail. Seems like that power supply has been around the block a few times but still kicking. We know that camera gets in your way if you could mount it over head pointing down at what your working on I'm pretty sure it won't be in your way. Thanks for all you do to bring us some more great videos 73
Nice repair. Guess it wasn't too difficult to remove the main board. The controller board might have been more difficult to diagnose due to its position. Blue Ringer kit ordered, thanks for the tip. Take care Peter.
Thank you. Right it was not to difficult to remove the board. As I already said before if you need to work at the controller board swap simply out the critical components as you can't take the pcb out twice...
Hi Peter, just watched and enjoyed this video again. Thanks for the warning not to use a valuable and precious scope for circuit measurements! To prevent scope damage, I use a 500VA isolation transformer, that works fine and prevent main voltage hazardous situations. Thanks a lot for all your great videos! 73’s, Nanko, PA0NVY
@@JohnUsp hi John, Thanks. You are right, the isolation transformer is used for the device under test, not to power the scope, I was not clear in my response. 73, Nanko
Good series here Peter. Though not seen here but I have owned switching supplies that are non-isolated that use an inductor instead of a transformer. A voltage sniffer would come in handy or this diagnosis...
@@TRXLab No it was A/C to D/C, what I remember about it was that it used an X-Rated Capacitor and a zener in the circuit, I have seen them with both a full and half wave rectifier. It seems like I remember some computer PSU's that were transformer-less? Sorry I don't remember much about them...
Very nice video. Professional work. For me missing the scope signal from both mosfet gate keys bcos I wonder over this trick: How it work and what for is implemented driving upper key mosfet gate via other transformer - so my question is: 1. Both mosfet are switching in this same time or this floating source gate doing any delay between up and down key? 2. What here is domination wind - from gate side or high side of transformer? Simply culd you explain how it work an why its implemented? btw. first time I saw forward 2t with two main cappacitors in series. Even for me I can put 2 caps on 400V for less stress this units. Also less current leaks when use 50% nominal voltage of cappacitors.
hi Peter. about reactive power, in france, authorities are actually changing our old power counter by a new model witch is a communicative counter call LINKY. but the new one is in VA... so most part of the french people (99.9%) don't know what it is about. so for some of them a big suprise are waittig them on their bill. As well as the subscription is generally for 6 kw, they will have in reallity less active power available. further more this counter is equiped with a built in cut off so if you exceed the power subscription it cut the line automaticly....big brother is in our house....creepy!!!!!
Wow that can get very expensive..The only way is to get around to start reactive power compensation. May be that is the reason that if people start to complain they get the advice to call the electrician?? Good trick by the power companies??
I connected my oscilloscope directly to the mains. Even though it was a battery one it made a right old mess of the innards. The thing made a noise like 1000 components crying out in pain.
Thanks so much for the videos. I normally watch your videos for the entertainment value mostly, however this time is different. I'm re-watching this one actually because the SMPS in my Icom IC-7800 stopped working. I know nothing about them. Icom expects you to replace the entire unit at $1550 USD and will not supply a schematic. I was very fortunate to find someone on the internet who had a copy that was drawn (reverse engineered) by some hams. I have 322V high voltage and I have an ACLV of 63volts. So here is my question, I have a scope that runs off of a battery. I normally keep it plugged in to mains power to keep the battery charged. Would it be safe to unplug the AC cord and run it off of battery power and it be safe to use to probe the power supply? Based on your explanation it would seem so but I don't want to try it and be surprised. I've only ever repaired one SMPS and that was on an IC-736 and all I did was replace all of the electrolytic capacitors. I suspect an old capacitor is the problem in the IC-7800 as well. Thanks for any advice.
great to see you back Peter. been following you for a few years now . could i use the same diagnostic to repair a Yaesu ft 990 internal power supply ( it started BUZZYING then just stop ) keep up the great work, say safe , all the best from the UK
At the input the transformer is fed with chopped DC. Not AC as you said!!!!. A transformer works by means of a change in magnetic field or magnetic flux. This does not necessarily have to be AC. There is also chopped DC at the the output of the transformer
I still have my old isolation transformer. I sometimes have some line noise and was wondering if the isolation transformer would remove the line noise. I think it may be coming from the refrigerator, just not sure. It could be some vortex over my QTH messing up my VHF frequencies. I've only noticed it on VHF and never HF. What you suggest? W Rusty Lane K9POW in eastern Tennessee
Greetings Peter, what a fantastic channel. Do you run a commercial repair workshop, that will accept repairs? Or is it only repairs for RU-vid ? Please do let me know. Many thanks !
Thank you. Well it is always a time issue as videos like this are very very time consuming and don't help to fulfill my daily job. But I will put it on my project list...
Great work! You write "no discussion we need a certified transformer on the DUT unit. 2: You do NOT need a second transformer on your scope but it makes daily business much easier as you do not always think about safety issues while you are working" I ask you: Does connecting the oscilloscope via the isolation transformer require that the ground wire is also connected or can it be left unconnected? Tnks
@@TRXLab You mean "leaving the ground wire disconnected would kill security", right? But the risk would only exist if there was a leak between the phase wire and the frame, or am I wrong? Thanks for your attention. PS: I apologize for my bad English.
@@TRXLab Sorry but I still don't understand, could you kindly quote the correct sentence between these two (we are talking about scope powered by isolation transformer): a) "scope ground wire NOT connected = kill safety!" b) "scope ground wire CONNECTED = kill safety!" Thanks for your patience :-)
@@scossa_vr - For safety - Do NOT connect your scope to any building or mains ground. The whole purpose of an Isolation Transformer is to "FLOAT" the scope.
Hello Peter great job please tell me, if I use the diff head. Test probe can really don't need what's called an Auto transformer, to get the flooting point and safety working with scope??
Could you do the same for my SMPS? It's from a Crate guitar amp. I fried something when a surge accured at my house. I can send you schematic if you could tell me where to probe at points to find faulty component.
I see the ring tester is no longer in production. How would I use a standard ESR meter to know if the coil is damaged if I don’t know the value the transformer should have?
Hi, could you tell me with my problem. I have smps 65v DC. The coil is whinning and no output. I've tried to check any capacitor but found no problem. Thx
better go right up to the rectifier bridge if no power you go down to the primairy if you do have power you go right to the secondary so you dont waste time
Why you connect smps and osciloscope through 2 transformers? Wouldn't just one on smps or the osciloscope isolate the ground? Aside from serious safety issues wouldn't just isolating the ground pin in the osciloscope plug do the same?
Very easy 1: no discussion we need a certified transformer on the DUT unit. 2: You do NOT need a second transformer on your scope but it makes daily business much easier as you do not always think about safety issues while you are working. That makes it much more convenient not always think about your test setup but on the problem you are facing . 3: no way to "only" disconnect ground at your scope. This really creates an incalculable serious safety risk. So having a second transformer keeps me isolated from ground and this practices works for many decades with me.
@@TRXLab Hi there, really good video, and I appreciated the emphasis on safety. I have had to make my own isolation transformer from stuff I have hanging around because from a hobbyist perspective buying this equipment is expensive. I am currently looking at a smps that's very complicated as it's out of an old HP spectrum analyser, and I have had to take care of the health and safety first! But what I dont have is a differential test device for the scope, I bet that's expensive as well, I probably will have to make one!
capacitors it’s smooth outs for an AC that’s converted to DC if a pure DC it’s doesn’t smooth outs what’s part it’s needed to add to causes it smooth outs examples 12volts DC connected to a 25volts capacitor the voltages stayed 12volts the same if using AC power converted to 12volts DC it’s smooth out almost 15volts but a pure DC it won’t works whats parts it needed to added to cause it’s smooth outs
