12V 2A power supply fix and analysis
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- Опубликовано: 7 сен 2024
- Repairing a 12V 2A flyback switching power supply, what's inside, analyzing it, reverse engineering the schematic, explaining how does it work and showing some waveforms on my oscilloscope.
The next episode - the transformer autopsy:
• 12V 2A switching trans...
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lol the smoking resistor at the 1 minute mark :)
It's just fear-sweat burning off.
Yeap :)
Your command of English is better than most Americans. I speak Fluent Spanish and some Russian but nothing like you did here. Great lesson!
lol... that's my donation... was used for a CCTV camera for a few years
thanks for the donation :). I was thinking it might have been for CCTV.... in the next video I will open the transformer.
my bet is that when the label said "suitable for electrical communication safety against monitoring", they mean: "suitable for electronic surveillance", because I have some spare power supplies very similar to this one that came together with some IP CCTV câmeras that I bought on aliexpress. They're designed to be mounted in a wall next to the camera outdoors, that's why it's water resistant IP43.
Yes, I think 监控防水电源 (jiānkòng fángshuǐ diànyuán) means waterproof PSU for CCTV. They probably mistranslated that. (防水(waterproof) is not to be confused with 风水(wind-water), the latter being called feng shui in the western world. :))
I like the cutout on your schematic which let you still read the channel's name.
That circuit looks identical to the 12 and 5v cheap power supplys for hard drive caddys.
I think you have a similar circuit on your site.
My frend had one fail that powered a caddy, i replaced the boiled caps and dead mosfet driving the transformer.
Added a much bigger heatsink and drilled vent holes in the case.
Crude but usable :-D.
Loverly quality control cat having a little nibble lol.
You probably know this already but when measuring power supply nodes on a scope, it can be of benefit to use a lower impedance probe. This can be in the form of simply a length of coax with termination at the scope, perhaps with a series resistor to form a 10:1 divider (e.g. 450 ohm into a 50 ohm coax into a 50 ohm terminator). If your net is high enough power that a 50 or 500 ohm load will not affect it too much, then this can often give better results than an oscilloscope probe. Just make sure you're not exceeding the power rating of your termination!
You might be thinking of a transmission line probe.
Probably not a huge difference on switch mode supplies, but i think I get what you are saying. The frequency should of the PSU and voltage of a regulated supply should not vary depemding on impedence or load. A load on the circuit, however, could make a difference when any faults that occur under load .
The testing methods used in the video are quite appropriate for small PSU testing.
Probably not a concern at the frequencies used in switch mode power supplies, but you also have to be careful of impedence matching. If the scope is 50 Ohm, your probe should be matched to 50 Ohm.
@Ralph ReillyThe 50 ohm terminator or built-in termination of your scope is a resistor and like any resistor it has a power rating. If you put through much current through it it could fail.
@@EsotericArctos So usually standard oscilloscope probes are high impedance and avoid reflections through the lossiness of the transmission line. This is so you can probe signal nodes without presenting a significant load to them and thus affecting the signal you're trying to measure.
With a power node, this is less of a concern (because it already has a much bigger load), and using a lower impedance probe can help you see just the real ripple/noise on the power node, rather than the probe picking up EM-coupled noise from elsewhere in the circuit. Especially in the case of, for example, a CPU Vcore which is often around 1 volt but at dozens of amps, putting a 50 ohm load on it is pretty insignificant.
Maybe if you add rectification to the auxiliary, kind of redesign it, and test it with a low power tungsten lamp in series to not kill it...
You could end up getting the 2A!
Try measuring the output voltage across the first electrolytic capacitor (before the inductor) and see if it remains at 12V when the PSU is loaded at 2A. I have a feeling that the inductor and the cable drop a lot of voltage.
I don't agree. --> 12.5V @ no load --> 12.3V @1.2A -->>> 10.0V @ 1.4A.
On the other hand, if you look at the inductor, it consists of a very thick wire with a very small number of turns.
@@daveamerion8177 hmm yea that makes sense. Going from 12.5V to 12.3V for a 1.2A load and then going all the way down to 10V for a 0.2A increase in current is obviously not because of the source impedance (it can't change from 0.16 ohms to 1.8 ohms). The psu can't deliver that much current. Thanks for pointing it out.
It's interesting that when you see Chinese mains plugs they always look like solid cast metal and never have the holes drilled in them. US plugs almost always have the holes and are often made of folded brass rather than cast metal. Oddly enough the US standard does not require the holes, only says that if there are holes they must be in a certain position and size. I did read somewhere that the prongs are not as long on Chinese plugs, so some US plugs may not fit in Chinese outlets. Additionally, China uses the Australian plug type for grounded outlets, which is completely different--although it's not technically Australian, as the dimensions are not quite the same but often they will fit.
say what you want, i think british plugs are the most brutal. from what i heard it is because they want their tee fast
3.5 KW teapot innit?
Those holes are there for easier twisting of bare wire on the prongs for quicker and safer connection to mains.
@@AlexanderBukh british mains sockets are wired in a ring configuration. The ring is fused with 25 or 30 Amps and the appropriate fuse for the appliance is in the plug.
The plugs themselves are rated at 15 Amps continuous iirc.
Depending on the installed fuse of course.
@@albinklein7680 13 Amp fuse in plug is standard in UK, if i remember right;
@@AlexanderBukh No one asked xD But I suppose brits will take any chance to brag about their plugs.
Dude, I never get tired of your accent. "Looks like they are using the same cable for the input and the output, which looks kind of reedikulooos!"
Looks like it was made with a lot of recycled components, they would not have used an EPCOS capacitor in there new, as it likely would have cost most of the price of the unit. Cheap unit, made cheap, and likely the 2A rating is extremely optimistic, probably only 1A, though of course with a lot of ripple from the poor choice of recycled inductor they used.
A nice looking 12v 24w psu
6:58 sweet cat you have.🥰 Thank you Dany, another great explanation!!🙂
Electroboom uploaded some wild diodes
You may also try to fix these horrible designs for better performance. Then we would learn how to practically design a good power supply. Just autopsy isn't enough for me. Anyways, thank you DGW for the videos.
What's DGW ???
sjuooper, as always, thank youoo
Thumb up because of the cat and schematic 😺
There doesn't seem to be much of a seal on the box to justify the ip43 "protection-against-direct-moisture-spray-at-angles-up-to-60°-off -vertical" rating, which is slightly worrying. It may crop up in the next video.
It doesn't need any seal to meet IPx3. It's not about water getting inside, it's protection against water having "harmful effects"... there is a BIG difference.
Also, the water ingress is measured in the mounted position. So, given the way that the mounting flange is constructed (integral with the main body), you would mount it to a wall then spray water from above and to the side.
In fact, the bottom (where the wires go in) could actually be completely open and it would still meet IPx3 since vertically falling water doesn't levitate uphill to get into the PCB inside the otherwise sealed housing.
@@johncoops6897 Ah... I see, thanks. I wonder what 'harmful effects" they were thinking of
@@johnwelbourn3811 - Reduction of safety or damage to the circuit. An effect that causes harm to anything.
Put another way, water that gets inside but doesn't do anything except fall back out again... then that is not a "harmful effect".
It looks like your scope is picking up some VHF broadcast noise at 12:10.
great analysis
Your voice makes it really hard to follow and pay attention :))
👏👏👏
Circuit diagram in this video discrapton attached... for downloading
The bulging capacitor is labeled "EPCOS" -- this is a brand acquired by TDK. I would be surprised if it's genuine. Maybe it was recycled?
propably recycled
Probably fake. EPCOS are likely the best caps in the world; if they are real.
Could even be both recycled and fake.
The fact that all 3 caps are different brands, is a give-away that the capacitors are recycled.
primary input ~0.3A, secondary peak current ~3A. The duty cycle on the scope shows why its failing to get 2A at the output. The ringing is surprisingly bad.
That moment that the video was cut as smoke was coming out.
very cool
So they use the tape to insulate the electric fields between primary and secondary but then put a capacitor between primary and secondary. Why not remove both the tape and the capacitor?
I saw a capacitor 50v 12000uf japanese capacitor in casino machine (power supply) and inside it is a capacitor 50V 1200uf. Also some circuit that the regulator 7805 but fake. It is 7812 ic reg but Chinese manufacturer use sand paper remove 7812 and print on it 7805
0:58 Says fine while something is smoking...
This is fine.
1:01... Mmmh, something is smoking...
I doubt simple flyback will provide even half an Ampere from 100V mains or that it'l start at all. Anti-spy though :) for the spy's mains: for 100V supply network fault condition undervoltage is 90V but spys will be cut off at 100V and for 240V mains network overvoltage fault condition is 264V but this PSU is 1V extra spy safe.
can i wish you run all converters/chargers on 400VAC line voltage ? just to push them to beyond the limits.
Very nice!
I was curious if we can convert a flyback smps supply from 0-12 volt.. The minimum i got was 3.3 volt but i need 0-12 volt... Is it possible i can give external supply to main switching control ic ... Will tl431 and other circuit work with it ??? Share your views.... It would highly appreciated... Thanks.
Hi! I have run into a tricky situation trying to add an illuminated ON/OFF switch to a LiFePO4 14.6v battery charger and it seems no one has ever done that. Do you offer paid help?
1:00 magic smoke!
Pretty crappy build quality for sure, but not extreme yet .
No transformer autopsy in this one? I'm somewhat disappointed :D
Tractor feed paper?
The cat needs a really good old fashioned sci-fi name, like "Passitor". Then it can sit on the surveillance proof screen in front of your Interossitor - And you can call him/her "Cat-Passitor"?!
I use a PC power supply instead of these death traps.
They're safer and can give lots of amps, and often free!
👍
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i have an old ATX psu that drops voltage on load. The caps are acceptable, not builgy, yeah it might be bad design?
With most conventional designs the 5v rail is tightly regulated and the 12v is only regulated by virtue of the transformer ratio between the secondaries. Since the transformer is non-ideal the 12v will drop a tiny bit when it is loaded and rise a bit when the 5v or 3.3v is loaded. The change on the 12v rail should be less than half a volt or so.
@@eDoc2020 12 Volt rail drops to 10V on 2A load :'D, on 3A load the psu suffers on 8.5-9V :'D The psu capable of 12A on 12V :D on 5V its 40A and on 3.3V its 14A :D
@@Uraim That's definitely too much voltage drop. One thing I didn't remember with my last comment is that the older-style supplies often don't work right if all the load is on the 12v rail. If you're only using 12v try putting a load on the 5v supply and see if that helps. One amp is probably enough.
@@eDoc2020 thats interesting, didn't know that :)
0:27 Tím myslí kamery a kamerové systémy na 12V
0:59 What is smoking?
the orange insulation of the wire touched the super hot resistor.
1:00 Smoke coming from finger. Does not seem right. :D
1:21 and I can already see the bad filter cap.
It's a 1A SMPS they slapped on a 2A sticker to sell.
Then it's your problem!
Where do you live?
1000uF in such a small can, doubt it is rated for much ripple current!
You need only one transformer to make an isolation transformer?
If the turns ratio is 1:1, then yes. I think his transformer is made by Indel, you can check their catalog.
@@RicoElectrico ah thanks
@@dinhcao7528 But I think above some power prices get so ridiculous you can do it cheaper with 2 transformers back-to-back. Which are also easier to find for free in scrap devices.
@@RicoElectrico I actually like to make one but can't find the transformers. Lot of people are using the microwave transformer but then they have to rewind the transformers.
@@dinhcao7528 MW oven transformers with rewound secondaries are terrible for most applications except maybe spot welding. Their idle power consumption is usually very high as they run almost into saturation, and they get hot. The windings are almost invariably aluminium to cut costs. They're hard to rewind because the cores are nearly always welded together and they often don't have proper formers, just cardboard, so you have to be very careful about keeping the windings insulated from the core.
I wouldn't bother unless you're absolutely desperate!
Sometimes the power transistor itself gets weaker and a new one costs about as much as the power supply ;)
Weaker? Ummmm.... no.
Maybe it wasn't reaching 2A because the wires are not copper and they are super DODGY? Maybe they were half broken internally?
It's not the resistance of the wires because the voltage steeply drops after increasing the loading current just a tiny bit.
So its probably a not very good design... The components used to limit the current probably have high tollerances or the design is dodgy and that's it 😂
ダイオード
Dodggyyyy
OMG the blue cap is already pregnant ...
1:00 smoke from the resistor?
Even more load
Maybe Chinese government is now monitoring the people using the equipment power supplies and the modbus communication for get in the CCTV or network equipment. But that power supply it is safe against that. LoL 🤣
nice accent, where you from?
What does your cat eat? It looks like salad 🤣 Is she vegatarian?😉
He fixes it first, then destroys it.
Jeesus. Those fake strain reliefs. There is no honor left in the world.
👋Where is the cat ? 😀👋
eating
Epcos... I'll bet that's a fake one.
rediculus lol
Bizarre speech intonation. Why do you speaks in this manner?
I guess the transformer is pretty dodgy.
i would guess the same, haha
You might be surprised :) wait for the next video ;) It will be available for my patrons today (or tomorrow) and public 2 days later.
Nice video but I can't put up with your accent sorry sound like my wife
speak slower!