I got asked if I could take a look at some LED strip and its power supply. The owner had received a small shock from the supply while testing the LED strip.
The series connected capacitors are to increase the creepage distance on the PCB and to prevent the output becoming live if one of the capacitors fails short. It is fairly common among better switchers.
I noticed mild pain when brushing up against cables (USB and audio) that were plugged in on the other end, so I eventually started poking around with a meter and came up with very similar voltages to what you measured. Glad that this is apparently working as intended and not an issue with the wiring in our house! On a side note, the same thing happens with my mixer: getting a mild shock whenever my lips accidentally brush against the metal grill of the microphone is ... rather shocking.
This is true for all switching power supply, the obvious way to eliminate shock is to ground the metal, some power supply has ground pin (the third/center pin), but some cheap power supply don't use it.
Electrical noise is generated by the rectifier diode on the low voltage side, also spikes on the mains can be coupled through to the output via capacitance in the transformer windings, these contribute to electrical noise leadign to rfi. On chassis supplies a screen winding can be added to the transfomer to prevent unwwanted high frequncy coupling, you cant do this with a wall wart that doesnt have an earth pin, hence the y capacitor.
The Class Y cap is to stop the output lead acting as an aerial for any RF on the secondary side of the PSU by capacitively coupling it to the mains side, which is is effectively earth. With a three-pin supply it should be connected to neutral, but with a two-pin one or ones like these where there's no identification of the mains input wires there's a 50% chance it'll be connected to live/line.
Hi Clive the suppression cap just provides a path to ground for RF energy from the low voltage isolated side coupled also with it's long lead (antenna ) back to the mains earth on the HV side..
with the connector inside that psu, i immediately thought BT cordless phone supply, the shape of the case is also similar. probably why it's built better
Ahh, that will explain why there's always a slight fur around the edge of my iPad and iPod when they are charging. Always wondered why I should feel it. Cheers!
@@DanaTheInsane Super old comment, but my original iPad power supply has 124V, and it definitely shocked me really hard one time. That is how I found this video.
I have a Meross power strip with USB ‘s and I found the floating AC voltage to be a nuisance, making touch screens erratic etc. (It can’t do sensitive electronics any good). So I took mine apart and connected the USB framework to mains earth and had no more problems.
Thanks a lot for this video and the explanation. I've noticed that a line tester lights up on most (5V) power supply output or the usb casing or even on the device connected to it. Do you know if it is safe to "ground" them?
I have a 10 Watt cold white cob on my upstairs landing that I think imitates sunlight better than warm white but CW are far to harsh for general room use.
This is exactly why I only use grounded (3 pin) mains power supplies with my laptop. When you are connecting to other equipment via USB, RS232, and Ethernet - you're playing with fire when there is 90 to 100V between your computer "ground" and earth.
+Daniel Astbury Daniel, actually with Dell U7809 power adapters, the mains power cord earth pin is connected to the DC negative. I am 100% sure of this as it can be tested with e meter between the earth pin and the outer shell of the DC connector on the end of the cord that goes to the laptop. There is less than 1Ω of resistance.
+davida1hiwaaynet also on some Dell systems like the Alienware laptops, there are actually 3 conductors passing through the barrel connection (the third being a tiny pin) to pass ground through separately and thus eliminate the need for audio isolation transformers on Hi-Fi equipment to stop buzzing. I used to do Professional sound for a number of years with a monster of a system using my Alienware laptop without the need of an isolation transformer.
@@djhenjin3425 A late commend and maybe not applicable. The latest laptop power supplies (applicable mostly to Dell) use a third small pin in the connector in order to communicate with the supply and verify if it is original or not. If not the laptops decide even to throttle the CPU for "security" reasons.
@@didaloca No, at first it seems the ground is not required, but in my experience, without proper ground (true ground to Earth) there will be electrical shock coming from Adapter/Power Supply when you touch the metal part of your Laptop (e.g. USB outer metal) or your casing (in PC, this is also true for PC). Ground is important, not only it eliminates shock, it also helps eliminate EM noise/interference that might cause disruption in voltage reading or oscilloscope.
Clive, I was under the impression that the USB power supplies were only supposed to put out low DC voltages. Whats going on so that my "device X" that needs (I assume) 5v DC is also receiving 100V AC? I know (i think) that a device will only pull the current it needs, but isnt the voltage forced on it? Am I making sense?
Great video and explanation. I sometimes notice that I get a slight tingle when I am using two devices that have switching power supplies. For example my laptop that has an aluminium case and my iPhone. I've just measured around 13v between them. I wonder if the person who submitted this was using two power supplies at the time?
In audio its called a "ground loop" and you should make sure all your gear is on the same ground and the use of a direct box will also help to eliminate a "ground loop" I have a ground loop between my desktop PC and my Mackie mixer board because they are physically plugged into different outlets on different circuits.. I been to lazy to install a direct box but now since its on my mind.. I just might do it.
I also bought 2 of this repurposed PSU but 5v 3a which look very good build quality.. but with the wires cut off in it too, I wondered where did they get these from, is there a Chinese company collecting scrap and reuse the PSU?
I've found a lot of the newer Apple Macbooks give you a tingle if you are bare foot and it's plugged into the mains. I measured the voltage between earth and the casing the macbook. It read around 115v AC.
It's possible the led tape was running dim due to the wire on the power supply being under sized. 5 meters of that tape will pull about 2A, and if it had that piddly wire you see on so many Chinese products, 12V could easily have become 10V by the time it got to the tape.
Think about the capacitive reactance equation as the frequency gets up to RF levels -- the capacitor becomes a better and better path back to the primary. This helps reduce the RF from the fast rising edges of the switching transistors.
Was going to say the same thing... the cap forms an LCR high-pass filter across the switching transformer with a center frequency "sweet spot" (dictated by the capacitor's value) designed to form a low ESR current path for the RFI pulses generated by the rising/collapsing magnetic field in the transformer. Is that about right?
you are so patient... that screwdriver head gets lose in each of your videos :) if i was on your place i would throw that screwdriver in garbage long time ago... once, twice and there is no third time in my dictionary...
My chargers minus(output) wire was directly connected to transformer and the other(output) one to a capacitor, not the other way around the circuit it should be,so i guess thats why it shocked me.
Why aren’t the USB shieldings connected to ground, to prevent any of that tiny current hitting me? Surely it would increase safety in case something is wrongly connected?
Hi big Clive my other half says do you ever measure the amperage in raisins instead of currents (It's only a joke from her by the way I am a trained spark by trade )
I've noticed there aren't any class Y caps in linear power supplies (bulky mains frequency transformer type). I guess the high frequency of the switching switchmode arises the need for the cap?
The class Y cap is designed to provide a path back for capacitive coupling through the transformer, which is more of an issue with switchmode supplies due to the close vicinity of the windings and high frequency switching.
How do I send something to you? I have a remote control from my cable provider that is partially functional and the tech tossed it in the bin. Could be fun to take it to bits, it apparently has 2 ways of connecting, RF and IR. Thoughts?
Have you took apart an Apple power supply yet Clive? See you have the big iPad one there but I have always wondered on the quality of the little iPhone chargers as they always seem to get quite warm during use sometimes hot.
I have two of those pink dual-socket "aulola" chargers and have been using them regularly for a while without issue... time will tell if they blow up my super-expensive iPad
+Ron Lo Well they both seem to work fine and the pins do fold most conveniently. I'm going to stick with them unless Clive actively exposes them as deathtraps and besides, I don't actually have an iPad, just a very not super-expensive Android phone and Windows tablet, both of which charge very happily without going bang.
Reptilian Capriccioso if it's well under a 100 bucks, then buy another one and take it apart. Use the tips for Clive's video and and buy like the usb power rating thing and the 1a load. Get a cheapy non rechargeable usb lamp and see the ripples in the rectifier etc. I think it may include bad stuff. Send it to Clive if you are 100% Baloney on electronics. You'll be featured in a video too.
While grounding (Earthing) will work to eliminate shock for non-faulty adaptor, you can see from the beginning that the adaptor does not have ground/third pin.
X rated capacitors will fail as a dead short, Y rated capacitors will fail as open circuit... The X rated caps are used on the mains hot and neutral for filtering and it's not critical for those to fail as open circuit, Y rated caps are used to connect mains to the chassis and earth and those must fail as open circuit to prevent the chassis going live and kill people.
It's capacitive coupling via adjacent windings and the interference suppression capacitor. You can have low voltage DC superimposed on high voltage AC.
I'm kinda confused... if you're getting this AC voltage through the power supply, how come it is still DC out? Is it because of different grounding or something?
No this shock is normal, a spillage static voltage build up from switching of high frequency. The shock is not from AC leakage otherwise the pain will be too intense. This is true for all switching power supply. This mild/moderate shock can be eliminated completely by grounding the metal or use power supply that has 3 pins (the third one is connected to ground) and make sure your house has proper ground (Earth) connection.
Of course, there is no connection from the AC input to the output. You'll find the ground/negative on the DC output of a desktop power supply connected through to the AC earth (so if you plugged in a USB into a desktop PC the shield will connect to earth). Are you suggesting doing this for shock prevention? (when plugged into a charger)
Most (almost all) USB power supplies don't have an earth, but do show capacitive coupling. I'd like to connect the shield of the USB connection on the charger to earth to avoid the tingle you can get sometimes. Mostly because I want to use it to power an electronics project that will involve my dog's metal water bowl, and I really want to make sure things are earthed. But I don't want to trip the RCD/GFI. Then I'd rather just not bother.
The current will be so small there would be no way an RCD would trip, it takes 30mA leakage to trip. A quick test on current leaking would be to get a multimeter and set it on AC mA/µA and put one probe in a sockets earth and touch the other to the metal case of the USB cable
I went electroboom on one of my Xiaomi Charger and touched it to my lips. And it gave quite a tingling sensation like the one you get when you lick a 9V battery. Tested the voltage and it was 88V
Unless ur really skilled at electronics 'which I ain't' it's hard to know where ur putting the other end of the test lead so next time could u keep everything in view cus I really like to learn, thanks in advance :)
iv e been shocked by a similar power supply but it was when i unplugged it the shock was from the 3 pin plug that u put in the wall not the small end that you put into the appliance
That would suggest there is no discharge resistor for the input capacitor. Very uncommon to see those or maybe the resistor has fried. It's not really very dangerous unless you poke the current between your left&right arm and give your heart a shock.
marioc65 If the device draws anywhere near 2A I tend to recommend going for 3 or 4A to ensure the supply runs cooler and lasts longer. Here's a link to where I bought it. www.ebay.co.uk/itm/171659726297
Gaf Yeah, I usually try to make these videos in a single take, but that one went off at a complete tangent that resulted in a lot more power supplies being opened.
Also, I have a sneaky suspicion that rubbery material might be a resin, as when I purchased some of this it absolutely wreaked reminiscent of epoxy. If that's the case, would it be unwise to just burn at the resin with a soldering iron?
Hi Big Clive, please can you tell me. I bought a charger to charge my Lipo batteries, its an expensive one & whilst I was charging a battery for the first time I touched the metal case & got quite a nasty electric shock, very painful, when I put a meter on the case it is showing 91.8 to 91 .9 volts AC, the case has this voltage all the time is this normal, I don't have anything else that does this. many thanks Dave oh yes forgot to mention, this charger has a built in power supply not a external one and it does have an earth pin on the plug, the charger is an Ultra Power LIpo Battery charger.
+dave v Many of these chargers do have a modest leakage current that will show up as a significant voltage in a high impedance meter. They can give a tinkle too. But if in doubt treat it as live.
Would this explain a weird phenomenon I experience in my home? I have a lot of extensions with RFI filters and lightning protection in them and a UPS for my pc's because I thought it would help get rid of man made noise on my Radio Scanner, but it doesnt sem to work well as an idea. I notice if I have to put my bare arm over a metal cased appliance like a DVD player to jiggle a scart or hdmi cable I get a mild burning sensation where my wrist meets the edge of the case. I also, for what ever reason, tried a neon flicker bulb in my bathroom (which is downstairs) and I noticed when I turned it off the tips of the metal in the bulb were still glowing faintly until you remove the bulb or turn off the whole house supply of power, why???? Also the same effect is witnessed upstairs on a GU10 ceiling lamp with LEDs on its edge of fitting. They were white and stopped working so I took them out and I put in place 2 Blue LEDs which came out my old kettle. The original LEDs used a capacitor dropper like you demonstrate, the ones out the kettle just use 2 fat resistors to light them. Now.. If I had a halogen GU10 bulb in, when you turned it off, all the light went off. If I used a CFL GU10 bulb, the LEDs would glow after switching off, If I use LED GU10 bulbs the LEDs go out after switch off, I cant explain this bane on my life and wondered if you could possibly shed any light on the situation for me, a possible cure perhaps, Im sick of getting tingles off things and Iv checked every earth wire on every fitting/switch and socket and its all earthed properly :( Even a mains tester (one of those screwdriver with a neon in the end) glows if you touch the fixing screws on light switches and sockets so it seems i have some earth leakage problem somewhere?? Im sorry for such a long post but you seem so knowledgeable in this field .
+JohnnyX50 Many appliances with switchmode power supplies and no ground give a very slight tingle to thin skin like wrists forearms and the back of your hand. It's microAmps, but you can still feel it as a slight sting. The lamps glowing slightly when off is common. It's the tiny amount of capacitive coupling and leakage between switch wires. Most LED lamps have a shunt resistor to try and stop that effect.
I have only just seen you have replied, my sincere appologies for such a late response. I did not expect a reply as I know you are a busy person, but I thank you so much for putting my mind at rest, I was going insane thinking I was going to need an electrician to come and check things for me (and all the tingles I was getting). Your answer makes everything so clear to me now, I never gave any of that any thought as I have no previous experience in it. On the funny side I can cancel the local vicar now to exorcise my house lol :) Thank you Mr.Clive once again :)
I hear you on that :) RF devices also hate FL lamps too. I scan Shortwave/VLF and LW Radio with a PCR2500 scanner for my pc and the noise they spew out is horrendous, especially in the 40+ Khz range which is why I am replacing all FL's with LED. I have a 5FT LED lamp in my kitchen now (about £17 at the time) after having so many tubes and fittings failing on me. Just ripped out the quick start electronics, banged L and N to the end sockets, fitted LED tube, Perfect, except its a very cold white, which I think Clive would cringe at. Its very clinic-y LOL
I am too recently having this "ac leakage" on (i believe) properly grounded power supply. By properly grounded I have readings 220v Live to Neutral, 220v live to earth ground and 2v neutral to ground/earth. When I plug in the power supply, I get nasty shocks from the frame of the psu and ground of secondary part of the PS. In your case most usb ac only has 2 connections live and neutral. Have you figure out what caused and how to eleminate those ac leaks ?
Sunaryo Suhwahyudi If your power supply is metal and should be grounded then check it actually is. If the ground connection is broken it may result in shocks.
Sunaryo Suhwahyudi If the power supply has a metal case then it might be worth checking the continuity between its case and the ground pin on the mains plug if it has one.
I can feel the 50hz vibration of mains cycles if I stroke my fingertips lightly over the metal of my wife's Apple iPad when it's charging. Apple charger is used. I am not particularly happy about this. Both iPads she has had have done exactly the same thing... (?) Any cause for concern, I wonder?
It's a common effect with switchmode supplies that have no ground connection. It's capacitively coupled current made worse by the fact that Apple use proper filtering that couples even more across.
OK, I'm not an electrician so can someone tell me if those voltages of 100V (or 144V in case of Apple power suplly) are acutally normal? My AC voltage is 220V (Europe). I found this video when searching for "power supply shock" after I got a shock using one of these generic 12V 1A power adapters with my Netgear network switch (it was not original PSU that came with!). The network switch housing is metal and while handling it with one hand, I touched a metal PC case with the other hand and got a shock. I then placed the switch on the PC case which created a spark and tripped the circuit breaker in my house. After some investigating I found out it was a problem with the 12V power supply because I could measure 120V between its output barrel connector (both + or -) and the PC chassis. I tested the rest of them I had in my room and none of them had this problem (they all showed 0V). So I decided to discard the faulty one to make sure it doesn't kill me. Now in this video I see that Apple charger also shows 140V. What's going on ? Isn't this dangerous if that voltage then comes to the housing of the device it is plugged into ?
That definitely sounds like it was a faulty supply. I only recommend using prominent branded units. I wish you'd sent the faulty one to me. The leakage from the apple charger is just at microamps, but enough to show on a sensitive digital meter.
It looks like the power supply PCB was just one from some scrap or extra stock someone had left over, put in a generic plastic case. Both of them seem like that. Ugh, that's the lowest of the low. Just re-packaging old stuff to be "new" again...
NICE video,thank you Better just to CUT off those (why or bypass) caps?? what RF is that,and what harm does it do? nothing? I had TWO Dell d830 laptops burn the mobo a week apart,until i found that the charger was putting out 91V AC; maybe it was a coincidence,but i do not use it anymore,i use some genuine Lenovo ones,that have LOTS of aluminum surround inside the plastic case,all around the pc board,and do not put out more than 1V AC out (besides the 19 V Dc,of course). I suspect it's the damn GOVs at it again with their flawed rules and regulations!! Who in their right ming would make a 19 volt DC charger that ALSO puts out 100 V AC??? only the GOVs,those pencil pushers!! I am in the car repair business and i see their flawed acts (the GOVs!!) A LOT..
can you take apart sloppy computer psus? i had a gtr psu and had it explode on me (after 2 years) but sadly i threw it away forgetting i could send it to you as i am quite a fan of you lol
Failure modes on junk computer PSUs aren't that exciting. Most of the junk PSU designs have a 188-250W max power rating and don't have any over current protection. So when you hit that magic number, whatever the weakest link is burns (usually a switching transistor.) If you never get over that magic number, they'll have other failure modes like the capacitors exploding or the fans failing.
@@GGigabiteM they can be exciting.... I've had a capacitor explode on me, which resulted in a loud bang, then blue, green and orange sparks noisily flying from the computer, then the house went dark 😁 how much more exciting can a device fail....
hey could do with your help I have a strand tempus dimmer and it I bought it as untested I wired it up plugged it in and it poured smoke I mean poured out the grills so opened it up and one if the boards some cables are fried just wondered should I make a video on fixing it and getting help
This buck boost voltage regulator worked alright for a while then shorted out internally and melted the wires violently almost instantly and gave me a nasty burn across my fingers as i tried to rip the white hot wires off of the attached input power supply. www.amazon.com/gp/product/B00SM3UALQ/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1 so it seems like it has no overcurrent protection on the input or output and no fuse! The wires became the fuse very violently! I recommend not EVER using this. Its really terrible.. Big voltage spike on startup. And if the input supply cant output enough current it cuts off and wont turn back on until you unplug the input supply and short the capacitor out then reattach the power supply (or input power source that you want regulated)
+ryan clarke Electrician in a heavy electrical engineering company (E J Stiell and Co) that specialised in steelwork power distribution and equipment maintenance.
The series connected capacitors are to increase the creepage distance on the PCB and to prevent the output becoming live if one of the capacitors fails short. It is fairly common among better switchers.
this video has answered a questing i have had for more than 2 years about usb audio systems and the noise some of them have
Socket & See continuity tester, goddamn that is comedy gold.
I noticed mild pain when brushing up against cables (USB and audio) that were plugged in on the other end, so I eventually started poking around with a meter and came up with very similar voltages to what you measured. Glad that this is apparently working as intended and not an issue with the wiring in our house!
On a side note, the same thing happens with my mixer: getting a mild shock whenever my lips accidentally brush against the metal grill of the microphone is ... rather shocking.
This is true for all switching power supply, the obvious way to eliminate shock is to ground the metal, some power supply has ground pin (the third/center pin), but some cheap power supply don't use it.
they don't call them Why-Caps for nothing. As in - "Why did I get a get a hell of a tickle from that?" :)
Electrical noise is generated by the rectifier diode on the low voltage side, also spikes on the mains can be coupled through to the output via capacitance in the transformer windings, these contribute to electrical noise leadign to rfi. On chassis supplies a screen winding can be added to the transfomer to prevent unwwanted high frequncy coupling, you cant do this with a wall wart that doesnt have an earth pin, hence the y capacitor.
Awww, you're not even going to stick a phone jack in that connector and see what's on it?!
The Class Y cap is to stop the output lead acting as an aerial for any RF on the secondary side of the PSU by capacitively coupling it to the mains side, which is is effectively earth.
With a three-pin supply it should be connected to neutral, but with a two-pin one or ones like these where there's no identification of the mains input wires there's a 50% chance it'll be connected to live/line.
Hi Clive the suppression cap just provides a path to ground for RF energy from the low voltage isolated side coupled also with it's long lead (antenna ) back to the mains earth on the HV side..
Thank You 🙂🙏❤️
with the connector inside that psu, i immediately thought BT cordless phone supply, the shape of the case is also similar. probably why it's built better
***** The telecom style connector did make me wonder if it was for some piece of office equipment.
bigclivedotcom I have an old, not original Nokia carger rated 12V 0,8A with that rj11 telephone socket on it.
Ahh, that will explain why there's always a slight fur around the edge of my iPad and iPod when they are charging. Always wondered why I should feel it. Cheers!
+Peedlebum You are using a cheap aftermarket power supply. Does not have to be an APPLE supply, but a good supply will kill that.
@@DanaTheInsane Super old comment, but my original iPad power supply has 124V, and it definitely shocked me really hard one time. That is how I found this video.
I have a Meross power strip with USB ‘s and I found the floating AC voltage to be a nuisance, making touch screens erratic etc. (It can’t do sensitive electronics any good). So I took mine apart and connected the USB framework to mains earth and had no more problems.
Thanks a lot for this video and the explanation. I've noticed that a line tester lights up on most (5V) power supply output or the usb casing or even on the device connected to it. Do you know if it is safe to "ground" them?
I have a 10 Watt cold white cob on my upstairs landing that I think imitates sunlight better than warm white but CW are far to harsh for general room use.
I found using a wire wheel for a Dremel tool at low speed works wonders to remove the coating off the strip
This is exactly why I only use grounded (3 pin) mains power supplies with my laptop. When you are connecting to other equipment via USB, RS232, and Ethernet - you're playing with fire when there is 90 to 100V between your computer "ground" and earth.
+davida1hiwaaynet
There's only positive and negative DC that comes out of the laptop power supplies, no earth. So the earth pin is unused.
+Daniel Astbury
Daniel, actually with Dell U7809 power adapters, the mains power cord earth pin is connected to the DC negative. I am 100% sure of this as it can be tested with e meter between the earth pin and the outer shell of the DC connector on the end of the cord that goes to the laptop. There is less than 1Ω of resistance.
+davida1hiwaaynet also on some Dell systems like the Alienware laptops, there are actually 3 conductors passing through the barrel connection (the third being a tiny pin) to pass ground through separately and thus eliminate the need for audio isolation transformers on Hi-Fi equipment to stop buzzing. I used to do Professional sound for a number of years with a monster of a system using my Alienware laptop without the need of an isolation transformer.
@@djhenjin3425 A late commend and maybe not applicable. The latest laptop power supplies (applicable mostly to Dell) use a third small pin in the connector in order to communicate with the supply and verify if it is original or not. If not the laptops decide even to throttle the CPU for "security" reasons.
@@didaloca No, at first it seems the ground is not required, but in my experience, without proper ground (true ground to Earth) there will be electrical shock coming from Adapter/Power Supply when you touch the metal part of your Laptop (e.g. USB outer metal) or your casing (in PC, this is also true for PC). Ground is important, not only it eliminates shock, it also helps eliminate EM noise/interference that might cause disruption in voltage reading or oscilloscope.
Very interesting,thank you..
Ahura called from the enterprise and want's to know, have you seen her communicator recharger?
Clive, I was under the impression that the USB power supplies were only supposed to put out low DC voltages. Whats going on so that my "device X" that needs (I assume) 5v DC is also receiving 100V AC? I know (i think) that a device will only pull the current it needs, but isnt the voltage forced on it? Am I making sense?
I have an old cheapo 12v adapter and if you touch the 12v it gives you quite the zap on a well grounded surface
This makes me think about when I was a kid, I touched the ground part of USB port in my school and it gave me hell of a shock.
Great video and explanation. I sometimes notice that I get a slight tingle when I am using two devices that have switching power supplies. For example my laptop that has an aluminium case and my iPhone. I've just measured around 13v between them. I wonder if the person who submitted this was using two power supplies at the time?
I love the name 'Socket and See'.
In audio its called a "ground loop" and you should make sure all your gear is on the same ground and the use of a direct box will also help to eliminate a "ground loop"
I have a ground loop between my desktop PC and my Mackie mixer board because they are physically plugged into different outlets on different circuits..
I been to lazy to install a direct box but now since its on my mind.. I just might do it.
I also bought 2 of this repurposed PSU but 5v 3a which look very good build quality.. but with the wires cut off in it too, I wondered where did they get these from, is there a Chinese company collecting scrap and reuse the PSU?
I've found a lot of the newer Apple Macbooks give you a tingle if you are bare foot and it's plugged into the mains. I measured the voltage between earth and the casing the macbook. It read around 115v AC.
I'm afraid the leakage is standard these days. To me that represents a step backwards in technology.
@@bigclivedotcom I agree. Especially on what's supposed to be a "premium" product.
It's possible the led tape was running dim due to the wire on the power supply being under sized. 5 meters of that tape will pull about 2A, and if it had that piddly wire you see on so many Chinese products, 12V could easily have become 10V by the time it got to the tape.
Think about the capacitive reactance equation as the frequency gets up to RF levels -- the capacitor becomes a better and better path back to the primary. This helps reduce the RF from the fast rising edges of the switching transistors.
Was going to say the same thing... the cap forms an LCR high-pass filter across the switching transformer with a center frequency "sweet spot" (dictated by the capacitor's value) designed to form a low ESR current path for the RFI pulses generated by the rising/collapsing magnetic field in the transformer. Is that about right?
Can you run that test on a modified sine wave?
Looked like an rj11 connector for a second there
you are so patient... that screwdriver head gets lose in each of your videos :) if i was on your place i would throw that screwdriver in garbage long time ago... once, twice and there is no third time in my dictionary...
Haha, agree with you there! I think it's because the screw driver has his name engraved on it, there's some sentimental value.
+IamIUareU
Well, it's a bit holder thingy, so the bit's are supposed to be exchangeable. That's par for the course.
does anyone know what screwdriver that is?
I've always wondered how he uses that thing for all the wrong things. I would be SO annoyed.
@joshuafarren DIY time with Tommy Walsh Mini Computer Screwdriver
My chargers minus(output) wire was directly connected to transformer and the other(output) one to a capacitor, not the other way around the circuit it should be,so i guess thats why it shocked me.
Bleed current should be at about 0.1mA from a Class Y1 capacitor. Nothing that will light an LED.
100uA will light a modern LED surprisingly brightly.
@@bigclivedotcom Maybe... Didn't try anything under 1mA. It won't "light" me tough :)
Why aren’t the USB shieldings connected to ground, to prevent any of that tiny current hitting me? Surely it would increase safety in case something is wrongly connected?
Hi big Clive my other half says do you ever measure the amperage in raisins instead of currents
(It's only a joke from her by the way I am a trained spark by trade )
I've noticed there aren't any class Y caps in linear power supplies (bulky mains frequency transformer type). I guess the high frequency of the switching switchmode arises the need for the cap?
The class Y cap is designed to provide a path back for capacitive coupling through the transformer, which is more of an issue with switchmode supplies due to the close vicinity of the windings and high frequency switching.
How do I send something to you? I have a remote control from my cable provider that is partially functional and the tech tossed it in the bin. Could be fun to take it to bits, it apparently has 2 ways of connecting, RF and IR. Thoughts?
Have you took apart an Apple power supply yet Clive? See you have the big iPad one there but I have always wondered on the quality of the little iPhone chargers as they always seem to get quite warm during use sometimes hot.
+Philip Sempers Alas, I need the one I have. It appeared briefly in the video I've just recorded, but the main subject was an IKEA charger.
Would a GFCI protected outlet prevent a shock from these power supplies, or is the current too low?
+jfenly No. the current is tiny, but detectable. Particularly if it quite literally "hits a nerve".
what is the difference between those cheapy chinese power supplies compared to the apple power supply? we expect better internals but is this true?
I have two of those pink dual-socket "aulola" chargers and have been using them regularly for a while without issue... time will tell if they blow up my super-expensive iPad
time to get a branded power supply, preferably not an apple one because most of them are fake, but something like eagletec, belkin
+Ron Lo Well they both seem to work fine and the pins do fold most conveniently. I'm going to stick with them unless Clive actively exposes them as deathtraps and besides, I don't actually have an iPad, just a very not super-expensive Android phone and Windows tablet, both of which charge very happily without going bang.
Reptilian Capriccioso if it's well under a 100 bucks, then buy another one and take it apart. Use the tips for Clive's video and and buy like the usb power rating thing and the 1a load. Get a cheapy non rechargeable usb lamp and see the ripples in the rectifier etc. I think it may include bad stuff. Send it to Clive if you are 100% Baloney on electronics. You'll be featured in a video too.
why not ground the port?
While grounding (Earthing) will work to eliminate shock for non-faulty adaptor, you can see from the beginning that the adaptor does not have ground/third pin.
Is that an RJ11 socket?
So every switching power supply has an ac output but with a limited current? D:
X rated capacitors will fail as a dead short, Y rated capacitors will fail as open circuit... The X rated caps are used on the mains hot and neutral for filtering and it's not critical for those to fail as open circuit, Y rated caps are used to connect mains to the chassis and earth and those must fail as open circuit to prevent the chassis going live and kill people.
Thanks man that was very helpful!I was looking for simplistic answer like this!
@@simplygame5530 glad to be helpful to you and thanks for the comment.
i know its an old video, but im curious why you would get around 110v ac on the supply with an earth reference when it rectifies to DC at the output?
It's capacitive coupling via adjacent windings and the interference suppression capacitor.
You can have low voltage DC superimposed on high voltage AC.
I'm kinda confused... if you're getting this AC voltage through the power supply, how come it is still DC out? Is it because of different grounding or something?
No this shock is normal, a spillage static voltage build up from switching of high frequency. The shock is not from AC leakage otherwise the pain will be too intense. This is true for all switching power supply. This mild/moderate shock can be eliminated completely by grounding the metal or use power supply that has 3 pins (the third one is connected to ground) and make sure your house has proper ground (Earth) connection.
Would it be safe to connect the shield of the USB output of a charger to ground? Given how low the current is, would an RCD notice?
Of course, there is no connection from the AC input to the output. You'll find the ground/negative on the DC output of a desktop power supply connected through to the AC earth (so if you plugged in a USB into a desktop PC the shield will connect to earth).
Are you suggesting doing this for shock prevention? (when plugged into a charger)
Most (almost all) USB power supplies don't have an earth, but do show capacitive coupling. I'd like to connect the shield of the USB connection on the charger to earth to avoid the tingle you can get sometimes. Mostly because I want to use it to power an electronics project that will involve my dog's metal water bowl, and I really want to make sure things are earthed. But I don't want to trip the RCD/GFI. Then I'd rather just not bother.
The current will be so small there would be no way an RCD would trip, it takes 30mA leakage to trip. A quick test on current leaking would be to get a multimeter and set it on AC mA/µA and put one probe in a sockets earth and touch the other to the metal case of the USB cable
Would you feel anything if you held the connections of the insulation tester?
Yes. They pass a test current of a milliamp, so they're noticeable, but not too fierce.
A faulty Y-cap is the reason why some people still get electrocuted from phone charger.
I have that same little dollar screw driver. Bet you got it from poundland huh?
I went electroboom on one of my Xiaomi Charger and touched it to my lips. And it gave quite a tingling sensation like the one you get when you lick a 9V battery.
Tested the voltage and it was 88V
Unless ur really skilled at electronics 'which I ain't' it's hard to know where ur putting the other end of the test lead so next time could u keep everything in view cus I really like to learn, thanks in advance :)
Party Pillz he said he put it reference to ground. Isn't hard. Any grounded surface
iv e been shocked by a similar power supply but it was when i unplugged it the shock was from the 3 pin plug that u put in the wall not the small end that you put into the appliance
That would suggest there is no discharge resistor for the input capacitor. Very uncommon to see those or maybe the resistor has fried. It's not really very dangerous unless you poke the current between your left&right arm and give your heart a shock.
yea didnt kill me but did give me a nasty bite it felt a bit like a camera flash capacitor
What kind of Megger is that.
Wonder why none of these have a resistor paralleled with the Y cap, or is that just done with X/X2 caps?
+Great Joe Is usually with the X2 caps across the mains to discharge them when the appliance is unplugged.
Clive I have noticed you don’t use fluke meters in your videos. Is there a reason for this or do you have “work” Meters and “home” meters.
I have my trusty old Fluke, but use this meter because it has a huge display. Fluke also represent poor value for money for hobbyists.
i need psu 12v 2a for portable lcd tv and i saw this you rewiewd on ebay. Will it be good for 12v 2 amp?
marioc65 If the device draws anywhere near 2A I tend to recommend going for 3 or 4A to ensure the supply runs cooler and lasts longer.
Here's a link to where I bought it. www.ebay.co.uk/itm/171659726297
bigclivedotcom Thank you.
11:30 - from the marks on the case, that's not the first time that your PS has been popped open :) Good video tho.
Gaf I noticed that too! You can tell he has movie/television experience, no worries Clive ;-) thanks for the vid.
Gaf Yeah, I usually try to make these videos in a single take, but that one went off at a complete tangent that resulted in a lot more power supplies being opened.
lmao I had one that claiming 10amp 12v untill it poped the driver IC cus some one repurposed it for lower amps lol
Don’t know how you got voltage on the Apple one, normally no metal surround in the socket ??? Maybe a knock off!!!
David Price why do you use so many questions marks and exclamation points? One is enough
Could this leakage potentially destroy sensitive electronic boards ? Thanks
It can potentially damage some circuitry if it is referenced to ground.
thanks a lot !
Also, I have a sneaky suspicion that rubbery material might be a resin, as when I purchased some of this it absolutely wreaked reminiscent of epoxy. If that's the case, would it be unwise to just burn at the resin with a soldering iron?
The apple supply has an earth pin. Not using it is the horrifying level of cheapness i've come to expect from them
Apple's products suck dix.
5:05 ''and this one's an Apple one so hopefully it's good''. What a vote of confidence ;)
When you tested the amps, where did you ground it?
Onto a grounded screw on some test equipment.
@@bigclivedotcom thanks man, i couldn't see where you put the ground of the multimeter.
Can multiple adapters with leakage cause a 30mA RCD to trip randomly?
Yes
what happens if you put the megger on your fingers?
You get an unpleasant shock, similar to those shocking pens and other toys
Hi Big Clive, please can you tell me. I bought a charger to charge my Lipo batteries, its an expensive one & whilst I was charging a battery for the first time I touched the metal case & got quite a nasty electric shock, very painful, when I put a meter on the case it is showing 91.8 to 91 .9 volts AC, the case has this voltage all the time is this normal, I don't have anything else that does this. many thanks Dave oh yes forgot to mention, this charger has a built in power supply not a external one and it does have an earth pin on the plug, the charger is an Ultra Power LIpo Battery charger.
+dave v Many of these chargers do have a modest leakage current that will show up as a significant voltage in a high impedance meter. They can give a tinkle too. But if in doubt treat it as live.
+bigclivedotcom thanks Clive much appreciated, love your videos very helpful and interesting
Would this explain a weird phenomenon I experience in my home? I have a lot of extensions with RFI filters and lightning protection in them and a UPS for my pc's because I thought it would help get rid of man made noise on my Radio Scanner, but it doesnt sem to work well as an idea. I notice if I have to put my bare arm over a metal cased appliance like a DVD player to jiggle a scart or hdmi cable I get a mild burning sensation where my wrist meets the edge of the case. I also, for what ever reason, tried a neon flicker bulb in my bathroom (which is downstairs) and I noticed when I turned it off the tips of the metal in the bulb were still glowing faintly until you remove the bulb or turn off the whole house supply of power, why???? Also the same effect is witnessed upstairs on a GU10 ceiling lamp with LEDs on its edge of fitting. They were white and stopped working so I took them out and I put in place 2 Blue LEDs which came out my old kettle. The original LEDs used a capacitor dropper like you demonstrate, the ones out the kettle just use 2 fat resistors to light them. Now.. If I had a halogen GU10 bulb in, when you turned it off, all the light went off. If I used a CFL GU10 bulb, the LEDs would glow after switching off, If I use LED GU10 bulbs the LEDs go out after switch off, I cant explain this bane on my life and wondered if you could possibly shed any light on the situation for me, a possible cure perhaps, Im sick of getting tingles off things and Iv checked every earth wire on every fitting/switch and socket and its all earthed properly :( Even a mains tester (one of those screwdriver with a neon in the end) glows if you touch the fixing screws on light switches and sockets so it seems i have some earth leakage problem somewhere?? Im sorry for such a long post but you seem so knowledgeable in this field .
+JohnnyX50 Many appliances with switchmode power supplies and no ground give a very slight tingle to thin skin like wrists forearms and the back of your hand. It's microAmps, but you can still feel it as a slight sting. The lamps glowing slightly when off is common. It's the tiny amount of capacitive coupling and leakage between switch wires. Most LED lamps have a shunt resistor to try and stop that effect.
Check florescent lights. They hate rf devices
I have only just seen you have replied, my sincere appologies for such a late response. I did not expect a reply as I know you are a busy person, but I thank you so much for putting my mind at rest, I was going insane thinking I was going to need an electrician to come and check things for me (and all the tingles I was getting). Your answer makes everything so clear to me now, I never gave any of that any thought as I have no previous experience in it. On the funny side I can cancel the local vicar now to exorcise my house lol :) Thank you Mr.Clive once again :)
I hear you on that :) RF devices also hate FL lamps too. I scan Shortwave/VLF and LW Radio with a PCR2500 scanner for my pc and the noise they spew out is horrendous, especially in the 40+ Khz range which is why I am replacing all FL's with LED. I have a 5FT LED lamp in my kitchen now (about £17 at the time) after having so many tubes and fittings failing on me. Just ripped out the quick start electronics, banged L and N to the end sockets, fitted LED tube, Perfect, except its a very cold white, which I think Clive would cringe at. Its very clinic-y LOL
I am too recently having this "ac leakage" on (i believe) properly grounded power supply. By properly grounded I have readings 220v Live to Neutral, 220v live to earth ground and 2v neutral to ground/earth. When I plug in the power supply, I get nasty shocks from the frame of the psu and ground of secondary part of the PS. In your case most usb ac only has 2 connections live and neutral. Have you figure out what caused and how to eleminate those ac leaks ?
Sunaryo Suhwahyudi If your power supply is metal and should be grounded then check it actually is. If the ground connection is broken it may result in shocks.
Hmm I need to do more meter readings. I get shocks but this one is definetely different at much higher amp I think.
Sunaryo Suhwahyudi If the power supply has a metal case then it might be worth checking the continuity between its case and the ground pin on the mains plug if it has one.
I can feel the 50hz vibration of mains cycles if I stroke my fingertips lightly over the metal of my wife's Apple iPad when it's charging. Apple charger is used.
I am not particularly happy about this. Both iPads she has had have done exactly the same thing... (?)
Any cause for concern, I wonder?
It's a common effect with switchmode supplies that have no ground connection. It's capacitively coupled current made worse by the fact that Apple use proper filtering that couples even more across.
#11:00 old nokia charger board.... :D
OK, I'm not an electrician so can someone tell me if those voltages of 100V (or 144V in case of Apple power suplly) are acutally normal? My AC voltage is 220V (Europe). I found this video when searching for "power supply shock" after I got a shock using one of these generic 12V 1A power adapters with my Netgear network switch (it was not original PSU that came with!). The network switch housing is metal and while handling it with one hand, I touched a metal PC case with the other hand and got a shock. I then placed the switch on the PC case which created a spark and tripped the circuit breaker in my house. After some investigating I found out it was a problem with the 12V power supply because I could measure 120V between its output barrel connector (both + or -) and the PC chassis. I tested the rest of them I had in my room and none of them had this problem (they all showed 0V). So I decided to discard the faulty one to make sure it doesn't kill me. Now in this video I see that Apple charger also shows 140V. What's going on ? Isn't this dangerous if that voltage then comes to the housing of the device it is plugged into ?
That definitely sounds like it was a faulty supply. I only recommend using prominent branded units.
I wish you'd sent the faulty one to me.
The leakage from the apple charger is just at microamps, but enough to show on a sensitive digital meter.
@@bigclivedotcom I could still send it over. I sent you an e-mail.
It looks like the power supply PCB was just one from some scrap or extra stock someone had left over, put in a generic plastic case. Both of them seem like that. Ugh, that's the lowest of the low. Just re-packaging old stuff to be "new" again...
Benjamin Esposti I suppose it makes economic sense if it is surplus stock. It's certainly much better quality than I was expecting in either.
NICE video,thank you
Better just to CUT off those (why or bypass) caps?? what RF is that,and what harm does it do? nothing?
I had TWO Dell d830 laptops burn the mobo a week apart,until i found that the charger was putting out 91V AC; maybe it was a coincidence,but i do not use it anymore,i use some genuine Lenovo ones,that have LOTS of aluminum surround inside the plastic case,all around the pc board,and do not put out more than 1V AC out (besides the 19 V Dc,of course).
I suspect it's the damn GOVs at it again with their flawed rules and regulations!!
Who in their right ming would make a 19 volt DC charger that ALSO puts out 100 V AC??? only the GOVs,those pencil pushers!!
I am in the car repair business and i see their flawed acts (the GOVs!!) A LOT..
high quality apple... made me laugh
made me rolf
Apple's power supplies are of remarkably good quality. Their actual devices may be a joke, but their supplies are of very good quality.
Luke Den Hartog - My CrApple power supply can't even supply the rated 2 amp.......It's a turd sandwich
can you take apart sloppy computer psus? i had a gtr psu and had it explode on me (after 2 years) but sadly i threw it away forgetting i could send it to you as i am quite a fan of you lol
Failure modes on junk computer PSUs aren't that exciting. Most of the junk PSU designs have a 188-250W max power rating and don't have any over current protection. So when you hit that magic number, whatever the weakest link is burns (usually a switching transistor.)
If you never get over that magic number, they'll have other failure modes like the capacitors exploding or the fans failing.
I noticed a hammer works quite well to get those PSUs working for a bit longer.
@@GGigabiteM they can be exciting.... I've had a capacitor explode on me, which resulted in a loud bang, then blue, green and orange sparks noisily flying from the computer, then the house went dark 😁
how much more exciting can a device fail....
I had one of those cheapo chinese usb power supplies blow up and knock the power out in the whole house
Apple not so good!
Ok, so the reason you are measuring v & i in ac is because the leakage would be ac? Sorry stupid question.
Interesting, the Apple power supply is clearly the most expensive but also seems to be one of the worst...
+Ron DLH Not so much the worst, but the one trying to be most compliant with interference standards at the cost of extra leakage.
It's actually the best (compliance wise)
hey could do with your help I have a strand tempus dimmer and it I bought it as untested I wired it up plugged it in and it poured smoke I mean poured out the grills so opened it up and one if the boards some cables are fried just wondered should I make a video on fixing it and getting help
looks like a old nokia charger
This buck boost voltage regulator worked alright for a while then shorted out internally and melted the wires violently almost instantly and gave me a nasty burn across my fingers as i tried to rip the white hot wires off of the attached input power supply.
www.amazon.com/gp/product/B00SM3UALQ/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1
so it seems like it has no overcurrent protection on the input or output and no fuse!
The wires became the fuse very violently!
I recommend not EVER using this. Its really terrible.. Big voltage spike on startup. And if the input supply cant output enough current it cuts off and wont turn back on until you unplug the input supply and short the capacitor out then reattach the power supply (or input power source that you want regulated)
...
For some odd reason your video sounds play on different speakers then most videos, it's quite odd.
+KoolBreeze420 What different speakers? What do you mean?
Clive, what did you do your apprenticeship as?
+ryan clarke Electrician in a heavy electrical engineering company (E J Stiell and Co) that specialised in steelwork power distribution and equipment maintenance.
Cool, Im an industrial Electrician as well. did my time in a sugar mill that had all the cool stuff but non of the fun.
B