I worked on a hi-pot tester for Sunbeam that put 1500 volts across blenders and other appliances to test for case insulation breakdown. Sharpest memory was of an engineer that couldn't understand why his O'scope couldn't handle a 1500 volt waveform. It was only rated to 1000 volts.

As a neophyte hobbyist, I learn so much from your wonderful videos. There is a lot to be learned from dissecting small simple electronic "doo-hickeys" and you make it entertaining and easy to understand. Thanks for doing what you do, Clive!

PS: Instead of botching a heatsink on the chip they should have used a chip with a lower ON resistance. But such a chip is probably too expensive for super cheap ebay items...

If someone needs a more scientific explanation, the 431 is a precision voltage reference, basically a programmable, more stable zener. The resistor divider is used to scale down the output voltage to 2.5V. The 431 leaks current to maintain a stable voltage and that current is used to control the led from inside the optocoupler. The capacitor is used for compensation, basically to slow down the reaction of the 431 so that it doesn't ring.

I saw your video last night about fixing a faulty remote control,and as the volume control on mine stopped functioning a while ago,I opened it all up,and found the contacts gunged up with some tacky glue which was preventing current passing through the connectors. I cleaned everything,even the case,and luckily it's now working fine. Thanks for the demonstration,very helpful.

Clive I continuously love your videos. I'm an electrical engineer and I learn a lot every time I watch you!

This reminds me of the too-long screw I found in a 200A/5V supply. It was shorting positive output bus bar to the case. It was not a problem in bench testing because our electronic load was floating. When it was installed, it wouldn't turn on because it was then both terminals were shorted to ground. The negative via the device wiring and the positive via the screw. The screw that belonged in that hole was just a couple of mm shorter than the 20 other case screws.

It must be ok though, it has a CE mark. 😆

Your voice is like a "Listening test" voice actor from my english class, epic, simple, fine

I enjoy the detailed schematic breakdown. Some key ideas finally clicked for me this time. Thanks again for the good work

*_American wiring colors:_* *Black* = Live: 60Hz, 120V RMS at 0º (phase) *Red* = Live: 60Hz, 120V RMS at 180º (basically inverted with respect to black) *White* = Neutral *Green* = Earth Black and red are the ends of the secondary coil of the transformer that feeds the whole house. Black to white or red to white will give 120V. Black to red will give 240V. 240V is reserved for certain appliances (usually high power stuff like electric ovens, air conditioning units and clothes driers. Worth noting: The NEC specifies that GFCI breakers be installed on a per-outlet basis depending on what room the outlet is in. (instead of having them in the distribution panel in the basement). The rooms and areas where they are required are typically where water may be found nearby. Hope that helps.

You can't measure the voltage drop of a diode in a circuit like this :). You have to use a scope. Without a scope, you have to take the diode out and try to apply the same DC current (but the actual voltage drop is slightly higher because normally in the circuit the current is pulsed).

Very appropriate cabling there for mains voltage ;)

Glad you posted this! I just got one of these in the post a few days ago (3.2A version, but looks pretty much identical), and though I've had it open to look inside (obviously) I haven't gotten around to actually using it.

Thanks that you have tried to measure the Voltage-drop through the diode and explained why it didn't work, I did the same fail and couldn't figure out why until now

To add to the power confusion, US household power wiring is black for hot (usually two of them), white for neutral, and green for ground. UN electronics wiring typically uses black for ground. So if you grow up working on electronics and then do some DIY household wiring, there is a very good chance of getting the colors backward if someone hasn't told you how it works.

What I read was that black for live came about from putting soot/carbon in the covering. In the original DC systems, return (-) was bare and then covered without soot. When it became feasible to use other colors and also with AC, some countries changed their color schemes but the US kept black as hot. So much of the electrical system is about cost. Higher voltages in some countries because it required less copper to carry the same power.

Looks like a nice simple supply clive, not much to fail really :-D. Yep they goofed up with the screw, but thats minor and can be fixed.

*_RAMMING_*_ it right up to 'ya._ I believe I found my new notification tone.

I've seen that problem in the past with an APC switched power bar. A customer complained that the power all of a sudden went off when the power bar switched the top connection. Turned out one of the screws that was holding the bracket in place was too long, hence it got connected to live and created a dead short to earth. I think that was a bit of a design flaw...

Thanks Clive, this just alerts me to check that screw on my two new similar power supply units I have bought from China factory a month ago and haven’t started connecting to two electronic projects yet. I

The warm output diode will be more efficient at 90C - its forward voltage goes down as temp goes up. Certain modern ferrite transformer core materials have a 'sweet spot' of minimum losses at around 100C - cooling the core would reduce the efficiency. High temperature operation isn't inherently a bad thing - thermal cycling is the villain, causing repetitive expansion/contraction which eventually work-hardens the conductors, which then crack.

No one gingerly pokes as well as Big Clive!

Interesting about the wire colours, I was working on the rear lights of US camper imported into UK and subsequently into Ireland and the person who had converted the lights (to insert an orange flasher and disabled the flashing of the red brake lights) had wired White as Live and Black to Earth and when I went investigating I found the live was Black - so the same colour issue with US cars as well - I thought I was mad but am glad to see you commented on the American Stuff being wired wrong

In the USA color scheme, red is also live. It's used in circuits that require 240V - I.E. directly connected across both _live_ busses. Red is also used for 3/4 way switches. Green/bare copper is ground.

I got the same 12V 2A LED power supply from ebay. The first one tripped a RCD and after that popped the internal fuse with a loud pop. I got a replacement that I have not yet put into use. I have just changed the case screw at the back so it has more clearance from the heatsink.

"Didn't go bang" awww - I wanted it to GO bang... Make something go bang. Set the magic smoke free!

Uh oh Clive, I just got a bunch of these exact power supplies..... thought they were not too bad aside from the soldered in fuse being too close to the metal casing. My screws were not overly long as yours. Installed a small piece of fish paper (electrical insulator paper) on the inside of the housing where the fuse is (and under the PCB) on all of them. Some electronic grade silicone to improve the isolation barrier. Plenty good now for for my application which is powering small test fixtures that have limited use. Chinese tend to overlook (not care) about these little details. But I have to admit they are otherwise well made and as long as the capacitors are decent, should last a very long time. A few that have long operating demand I upgraded to Panasonic EB capacitors.

Here where I live code allows red wiring between the light switch and the fixture, and/or between 3-way switches. Makes it easier to identify which wire goes where when working on a switch.

The 431 is a programmable zener / current shunt which is very stable with temperature changes.

Clive, a slightly better diode you could use is an STPS10L60 ... it's rated for 600mV drop at 10A ... or around 400~500mV at 3A. (It varies depending on junction temperature - high junction temps, lower the Vf.) The one on that PSU is, I'm guessing, an SB360 or similar type (Maybe an SB560 to make it slightly more efficient.).

Sir BigClive! Thank you for the video, I have to watch every one. I live in a large house and trying to go all LED, rather than the 55W bulbs that litter the place.. Looking at the worktop / sink area I'd like to put LED tape, are there any good drivers and perhaps a video how the drivers would be installed given the existing lighting is those fluorescent bars.. they have to go! There are some plugs but the toaster is in one of them.. Be well

Black and red are both live in American wiring when using 120V split-phase to make 240V. (Also blue in three phrase.) Red is also used as the extra conductor for three-way light switches and such. But yes, white is neutral and green is ground.

In the US black is live in AC, but negative in DC. with 220v AC black and red are live 110v legs that add up to 220v.

You could use your scope for measuring the voltage across the diode.

I had one of those go bang on me, the legs of the 470uf smoothing cap went thru the isolation in the case

+bigclivedotcom I can confirm that in the US split phase colors are black or red for hot; white for neutral; and green for earthed. Transformers here have multiple taps to produce 110-120VAC that is delivered to residential customers.

Fun is mounting it, as the one screw is fine, as it hits board only, but the other grinds into the one side of the rectified Ac mains. Nice big skid mark when that finally arcs through the solder resist and flashes over. The heatsink on the power switch is nasty, so it is likely that the failure will be flash over to the heatsink from the drain pins first, then the heatsink can flash over to the case. 2 output caps is more for cost reasons, the 2 smaller caps are cheaper than the comparable big one, as the small ones are more common in volume, and thus cheaper when you buy a million or so of them, even if you need 2. Plus you can cost reduce later on and simply remove one from assembly. No need to have extra caps on hand, if running short in assembly just leave the one out.

I'm a subscriber from the US!

You owe us a fuzzy pink Valentine's Day video/ artwork. Even Stewart mentioned you.

Surely the *screw* would become the conductor? So it would be on the thread area of the body.

A scope on the diode would be interesting

Use an oscilloscope across that diode, Clive! Then you can calculate the dissipation. Thanks for the video of a potentially fatally-flawed power supply. A shorter screw, or even a nylon one, should be enough to make it safer.

Thanks for another great video Clive, made me wonder if anyone else would be interested to see a video comparing constant voltage vs constant current LED power supplies along with how to find the right supply values for LED tapes? Cheers

The best way to test the voltage on diode 19:00 is to use an oscilloscope. And see the constant and variable component.

In most slavic countries old colour code was black for live blue for neutral and there is no earthing.Three phase on other hand varies a bit but in my country it is red green yelow in circuits with bus bars and for cables it is black brown and grey.Blue is neutral and ground combined.

I was waiting for your exclamation over the diode voltage drop.

lol, while watching this I spilt about half a bottle of alcohol on my desk and me while my gas-powered soldering iron was on. Thank goodness I punted away the bottle of butane away before it blew and set me on fire... until I looked down and noticed I was on fire. .. at least I don't have to shave anymore...

The control chip appears to work similarly to the TNY279PN which just happens to be in the faulty Vodafone Sure signal (v3) I'm presently working on. Looks like the chip exploded and damaged the mains input cap, causing it to go short circuit and blow the PCB fuse! Just received the parts from Farnell, but it was a bugger to get a sufficiently short (due to compact design) 22uF 400v cap!

Correct black in home is live and white is ground , in cars when American made red is live and black is natural ac is very clear and auto is very clear till they started the scam in 1977 with cars being no color code on high dollar car's , grey white seemed to be the worst on GM for no ref , just tell us to replace entire loom ! Game for sure !

Red and black are the colors used in U.S. also for 240volts. And, black is line and white is neutral for 120volts.

The mounting screw stand-off that attaches the Earth to the case looks like it would be very close to shorting to the Neutral and 0v tracks.

bigclivedotcom But the live pcb tracks have limited clearance horizontally to the case unless there is insulation all around the pcb edges. 3mm I believe from live to earth. Also the earthing connector should be separate from any mechanical fixings to meet current safety standards.

Wow ,the FLIR is awesome in checking components temperature. Wish I could afford one. They have so many uses.

The color coding here for single phase is generally black is live and white is neutral on a 120V line and black and red is 240, both considered to be live.

A Fast Max function on that DMM might have done the trick on the output diode.

Clive It has the European CE to Chinese Export mark so it should be safe Ho Ho. Use to visit an large switch mode power supply manufacturer in the South West for two diffrent standards company's. The quality manager fully tested all rebaged power supplies and their own to check they met either IT or other standard, usually international ISO/EN. You would have had a field day there. The dielectric test's on amps was intresting especially when they failed, reminded me of ElectroBoom. There approvals lab had 4 permanent staff, he would sign/pass anything unless it passed all tests, not the CE one. It now is part of a large Japanese coperation. If the products do not meet the standards, main one is crepages and clearance between mains and secondary circuits and earrthing ect you should send it to your local Trading Standards. As some one is going to be or has been hurt, killed or have a fire or both. Thanks for your very technical and entertaining videos, love your cap.

In Germany a few (and some more) years ago, i think this was in the 60ies we had red colored wires as earth connection in house wirings which was often confused with live... making some plugged-in devices very ... interesting .... also in cables with more than 1 wires, the red one was sometimes a switched live connection or L2 in 3-phase cables... which was a really reasonable decision ;-)

Sandpaper! Angle grinder! Good ground connection.

Back in '73 when I was discharged from the Army at Fort Bliss Texas, I needed a car to drive home. The beautiful Buick that I had lost her high gear, and I didn't think she would hold up 1000 miles in second, so I traded her off for an old Oldsmobile Vista Cruiser Station Wagon. Some kid had owned it, I would guess as the front seat was held in with coat hangers wrapped around them and part of the floor boards, the shift had been moved from the original automatic on the column and a 4 on the floor was mounted, a 4 speed tranny was mounted, and the turn signal lever was missing completely. So at that time I was studying Central Office Repair at the Army Hospital, as a step from Army life to Civilian life, so I asked my instructor for a couple of diodes to use so I could build switches to use for the turn signals. He gave me some huge diodes, I don't recall the number or rating, but he figured they should do the trick, so I took them and mounted them in line putting a left and right switch on each side or a wooden T-Shift lever I had carved for the car. IT WORKED - - - - until Denver, when the diode on one side caught fire after I forgot to cancel my turn signal, burned the hell out of the wooden shift knob and my finger when I tried to disconnect it.

at least you used the right wire colors for hot and neutral :)

You need some kind of electronic load for higher power/voltages.

Odd that the input rating does not just state 85-240 VAC. Splitting the ratings implies to me that there is a selection that needs to be set inside. Would be interesting to see what it does with the low AC voltage input - might work?

I'm ordering a load of these so I can give my house that "Tron" lighting theme.

I’m not really into wire stuff but it’s nice to see you open up shit

You are correct RE: US colour code Clive

I have seen many of your presentations so I think you missed something the chassis mounting screw was the correct length so it could contact the heat sink increasing its effect size by using chassis too

I suggest putting the overlength screw in from inside the box. Then it'll get shorter as you tighten it.

Yep, Black or red is live and white is neutral. Though I do like the method for remembering that Brown is live in the UK, because thats what color your pants will turn if you forget.

Awesome video

Note the interesting MOSFET in the power supply chip, it has four terminals. The extra terminal is for a second emitter. This is commonly known as a sensefet The extra emitter is connected to a few of the cells and emits a small current which is a defined fraction of the Drain current allowing the current to be measured with low dissipation. It's a current control mode chip used in a voltage regulated circuit. The current control mode provides automatic overload current limiting and start-up surge limiting plus simpler stabilisation.

The steel is electrolytically galvanised and the the surface is phosphate treated to provide an 'anti-fingerprint' effect. It's not at all reliable therefore for a connection unlike British Steel's *Zintec*(tm) which provides an excellent conductive surface. In Asia they seem to be really keen on the phosphated stuff which is a pig if you want a decent chassis earth.

most of these cheap power supplies you will find online that Majority of the ones on reviews, have "IT CAUGHT FIRE" type of review...... i purchased 2 300w 36v ones for a led bar. one immediately exploaded. and the other turned on but started smoking , i found that the ground wire, was touching the live Rail in the pcb . cheap power supplies for LEds' are built with living on the edge in mind .

Thanks for sharing 😀👍

I've seen red/black as live(different color per phase), white as neutral and green or bare wire as earth.

a fast switching diode (FS) also called a shotkey diode has a lower voltage drop across it than a generic diode 0.7V vs 0.5V I believe. they are much more efficient in stuff like that but they do have a larger reverse current than normal. still pretty negligible. sometimes used in bridge rectifiers as well for the same reason.

Nice wee PSU. Have to get one but the postage from UK to Ireland is nearly twice the cost of the supply itself!

The awkward thing is I have a power supply which looks _exactly_ like this, in fact I'm sure it's the exact model. Mine hasn't arced though. I replaced it with a different supply with a battery backup months ago.

I always remember black death for the American wiring worked for American company in the UK.

Looks a bit screwy to me 🤣

Speaking of arcing power supplies, my laptop psu is making an audible click/buzz noise every few seconds. I can't wait to see the arc stains when I get a replacement :D

Clive, you just hate to use that free Keysight scope you got :)

These cheap SMPS are a menace. Many of them contain no suppression components and dump huge amounts of noise onto the mains wiring and along the supply leads. This causes terrible interference to any radio set nearby. Looking at the one you have there, it seems to have no filtering at all.

From the US. Colored wire(aside from green) =Hot, White or gray =grounded conductor (neutral), Green =safety grounding conductor. Casual industrial color code - Single phase 120 VAC - Black = phase, Blue or Red = switched lead, Single phase 240 - Black/Red = phase - White=neutral. 3 phase 208 VAC = Black/red/blue = phases, white - neutral. 3 Phase 480 VAC "Y" - Yellow/Brown/Orange = phases, Gray -= Neutral. Normally RED/Black would be thought of as DC supply. (whew)

Clive, the first things they omit on these supplies is overcurrent protection. I've seen cheap laptop chargers melt their chassis due to an overload. Try and see how much you can draw from this, I'll bet you can get 4A from it or more

I nearly burnt my place down forgetting about a cheap Chinese water heating element with zero cut off or thermostat, hope everyone's proud of me. It boiled away huge pan of water then started melting and was on fire when I got back to it! Genius!

Hey Clive, can you maybe do a comparison of USB meters/testers?

They sell a power connector for LED strips much like a laptop brick. Not an expert but but the AC mains wire is very cheap and can pull away from the insulation exposing the live wires. I don't think LED strips are bad,per se, but there is no provision for fuses. I put them under the cabinet but opted for a one amp fuse at the power source. I've seen videos how these things can get so hot, so very quickly and the power supply doesn't recognize a fault.

✌ *_"Heatsink"_* ✌ : a folded up cupboard fixing. Clive: _"I'm liking this earth terminal..."_ - *I SHOULD HOPE YOU ARE - IT HAS POTENTIALLY SAVED YOUR LIFE!* :D Which baboon was in charge of choosing the screws? Wow... that's.... erm... silly. Clive, did you know that the reason POTS telephone line (or "battery" voltage, as it is known) voltage is +/- 48VDC is so that the high potential can overcome and breakdown poor connections and corroded joints, and allow the voice conduit carrier (the +/- 48VDC) to keep the signal flowing from exchange to CPE (Customer Premises Equipment - these are UK terminologies)? My point is this - if +/- *50VDC* can arc and bypass corroded joints/high resistance joints, then 240VAC *WILL DEFINITELY* jump across this negligible barrier of... say, what - a few MICRONS or less (I know you know all this, it's for the benefit of the viewers/commenters) - learnt this stuff back in the 90s.

Clive- in USA- black is always hot -green ground- white neutral. Absolute nonsense I know luv the wit man

I'd be curious about how much current goes back though the diode when the voltage reverses. Standard diodes at 50/60 Hz isn't a problem, but you get up into KHz range and the diode doesn't shut off that fast. You have to use a fast recovery job, but I think even they have some issues switching off. A simple circuit with a variable frequency signal generator as supply, a load resistor and a scope on the output would make a good video. Either that or use a "sense" resistor between the diode and the filter cap and scope the voltage developed across it.

So the circuitry and PCB them self where fine, but together with the casing it became dangerous. Likely they tested them separately.

en.wikipedia.org/wiki/IEC_60446 The preferred colours for AC phase conductors are: L1: Color wire brown L2: Color wire black L3: Color wire grey For a single AC phase: Color wire brown Neutral: Blue Protective Conductor (Earth): Green and Yellow (There are exceptions for US, Canada, Japan)

US is slightly more complex in that older homes were wired by previous owners who didn't follow any kind of specs.

Thanks Clive, I just tossed my cookies... Again!

it's odd how some of your videos are on the center/sub channels of my 5.1 but most other videos are on left and right. neat edit: i only noticed this when some of your videos go silent because i have my speakers mirror left and right to the other speakers. it ignores rear and center/sub channels. so the audio goes silent.

Was keen to see ifyou'd 'upgrade' that diode & retest for heat...

0:56 you are correct!!

perhaps grounding is more concerned with the threads than the partial connection to the top of that coated stand off...

05:52 - "I'm going to blow this up", I have never been so disappointed!