Testing a cheap power supply 

As several people have helpfully pointed out, I got the NTC/PTC thermistor mixed up. Mea culpa. Also, I have some additional power resistors on order so I can test this thing further toward it's limits.

Nice teardown! Safety seems quite legit for me as a former SMPS developer. Of course you can not check the Y-capacitor but the spacing together with the slots in the PCB may be okay. My next point of interest would be the transformer itself. Primary and secondary windings need double or reinforced isolation, so enamalled wire of primary must never touch enamalled wire of the secondary. The standard transparent isolation of the wire itself counts only as one isolation, so either they must use specially qualified "triple insulated wire" that is clearly yellow or they need additional insulation sheets between the windings. Transformer quality mostly is a quite good indicator for the security awareness of the producer.

That NTC thermister is for inrush current limiting into the cap at startup

The NTC resistor is actually a "Soft start" resistor. The resistance is initially high when it is cold and decreases as it warms up. So it limits inrush current. PTC resistors increase in resistance in response to temperature and in special cases are used like resettable fuses.

Looking forward to part 2 😃 I didn't quite see why the anti tracking distances would be insufficient, particularly as I see loads of other issues...

What I didn't see is proper rfi filter so better don't use nearby ham radio operators or general radio receivers. Ntc is OK, inrush protection. Hope that's an y3 cap

I am always impressed about the tiny little converter ICs which are used to drive a single MOSFET for 200 W of conversion power. Lately I have ordered a bunch of synchronous buck converter SO8-Devices which are capable to drive directly 100 V at 5 A for 250 W of power through this very tiny package.

Non existent fuses are great. They never fail.

if it had noise filtering eg a common mode choke and poly cap, it would be an ok psu

It works! You could always add some parts if you think you need them later.

Okay, those green and gold caps are known to not be what they claim to be. I don't know who makes them, but I think they are rebadged Xmas decorations... The temp rating is out by about 50%, had many dry out across smaller SMPS - better to replace with known good caps next voltage rating up.

Seems to perform as advertised, good for LED's, and a reasonable buy for what you paid for it.

I would add a fuse holder or use a fuse on the input but otherwise good enough for LED strips.

I used a similar psu for a bench power supply. Put it in a box with a fused ac input. Output to a 12v auto socket. I have a fused 12v plug from radio shack that has banana jacks that I use for 12 volt stuff and a good quality car phone charger for 5 volts.

The isolation is provided by the slot and the optocoupler, which looks ok. The other point is what is the rating of the cap, is it a safety cap or just a high voltage one. I'm surprised that they didn't specify it for the full input voltage range so it could have a worldwide market, after all its just a lower voltage limit, maybe they had issues with the lower level. Or they have never tested it in the first place and expected it will work ok at 180V. The lack of components for conductive or radiated emissions hints at it having never been tested to any standards as well. The only problem with the input voltage level being lower than rated is whether the components can handle the extra current in the input circuitry at full load. Its about an extra 0.5A flowing through the input and the transformer. Dont sound much but its about 50% more. 200W/180V =1.1A 200W/120A = 1.6A So as long as it starts up ok at 120V and you keep the load to around 100W, change the isolation cap to the correct type it should be usable. But always wear wellies if touching the output when its live.

I bought 3 of these a while ago and tested them with an electronic load. Each was barely able to deliver about 1/3th of the advertised power before breaking down. I got a refund from the seller.

Nice.

A very thorough test. 👍 It seems pretty solid to me. Definately mislabled on the input voltage. I'd trust it.

that supply looks OK I would trust it more or at least a much as the little plastic covered LED drivers. I use some really big power resistors built some into a kind of decade box totally passive to push thing till they start to sag

Good value

hi, you were saying about the NTC, isnt that inrush limiting?, it would be a PTC for operating current limiting?

Beyond all this pile of stuff, this time an absence of a proper DC Load became apparent.

Many of these cheap units have copper clad aluminium transformers and secondary side inductors (for Forward converters). They cripple these units in a thermal sense, as there's lots of losses. I bought a 400W 24V unit for shits & giggles, and it struggles to even reach 80W without dropping 5% at the output. It gets absolutely roasted at 50% load, and shuts down with time. And yet my 24V unit looks better than yours. The assembly and design is nice.

So glad I stumbled upon your channel recently being a ex-pegger I miss the accent please keep up the great work.

and the surface mount passives you were worried about were protected pretty well by the routed out slot?

Hmm, this is a 200w device, and you tested it with just 36w. For 200w the price would be great, not so much for 36w. Mine dropped to 11V at 5A and turned off at more than that.

Doesn't look like the voltage doubler for multi-voltage is there. Wouldn't there be 2 input bulk caps?

My bet is that is not a class Y capacitor in reality but justa standard 1KV blue capacitor 🙂

There should be 2 output diodes. Only 1 has been installed. With only 1 output diode, i don't believe the 16. 67A current rating that the label says. You should replace it with a matched pair.

You wouldn't use it on any thing flammable? Unless your house is made of stone or steel that is a hard one.

100 veiws in twenty minutes, doing good.

The NTC is not what you think, it is an inrush current device and is supposed to be hot when normally working.

What about 200W test, these devices likely will not do it sustained!