AliExpress MOSFETs Are They Real or Fake? Why Did My Repaired PSU Blow Up AGAIN?

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Sometimes you can replace the faulty components in a switch mode PSU only to plug it in and watch your shiny new parts self destruct. I recently have this problem with a power supply that blew up even though it was connected to a current limiter (light bulb). In the previous video I reverse engineered the PSU and eliminated just about every possible reason for it to fail again. What I was left with were either fake Replacement Mosfets or a couple of hard to test fault conditions.
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Опубликовано:

16 сен 2024

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Комментарии : 159

@LearnElectronicsRepair 19 дней назад

*It seems I'm featured on Hackaday again* hackaday.com/2024/08/24/comparing-aliexpress-vs-lcsc-sourced-mosfets/ For anyone interested we also tested the RDSon of these mosfets on the live stream ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UmdEpzmz6e4.html

@copernicofelinis 26 дней назад

Y'all need to learn unit conversion: one Chinese ampere is 0.25 SI amperes. One Chinese volt is 0.5 SI volt. Also, the chemical symbol of copper is "Al".

@georgeprout42 26 дней назад

And the CE marking on dodgy devices means Caveat Emptor.

@LearnElectronicsRepair 26 дней назад

@@georgeprout42 hehehe

@julescircuits845 24 дня назад

🤣🤣🤣

@ericksonengineering7011 20 дней назад

Ah, that explains a lot! 🤣

@mickwolf1077 14 дней назад

when they rip off their own property they again convert their units to their units which leads to more problems. lol

@gastube22 23 дня назад

Good video - thanks. There's shed-loads of fake semiconductors out there. I had a similar problem of blowing mosfets (genuine ones) in a high-power amplifier PSU, and reluctantly suspected the transformer. Thankfully I was in the happy (and unusual) situation of having another nearly identical amp to compare with. A shorted-turn transformer will have much less primary inductive reactance (compared with the resistive part of the impedance), so, as an alternative to the ring method, I checked this by disconnecting one end of the primary on the good PSU and injecting a sine wave at 20kHz (the highest I can get from my audio generator - nearer to the operating frequency of this PSU would have been better). The sine wave is injected via a series resistor selected to show an approx 90 degree phase difference between the voltage dropped across the resistor and that across the primary, seen on a basic 2-channel scope. Something a bit less than 90 was obtained with a 4.7 ohm resistor. Then I tried the same on the faulty amplifier and got something around 15 degrees with the same resistor. No need for any expensive LCR analysis equipment, and no need to remove the transformer as this is done at very low signal levels that are insufficient to turn on the secondary rectifier diodes (I had checked these were not shorted). This seemed very conclusive, and was proved by removing and dismantling the transformer (destructively) - it looked fine on the outside but the primary winding was badly temperature-damaged. [Without the good amp to compare with, I'm not sure this method would have been so practical - but an approx resistor value to use could perhaps have been calculated.]

@johnwest7993 13 дней назад

That's some seriously professional troubleshooting technique. Orders of magnitude better than when I was doing troubleshooting on a spy satellite project for the government and I requested some circuit info from my boss about a custom IC, and he asked me if I could repair the circuit without the info. I replied that without the info I could only repair it by swapping out the IC's one at a time until the bd worked again. He pointed at 1 corner of the board and said, "Why don't you start there." It took 3 days and 23 IC's to repair it, and I was infuriated at having to do something so time consuming and stupid. So my compliments to someone using their brain and knowledge of electronics to identify a tricky electronics failure. You must not work on spy satellites. :)

@jackipiegg 26 дней назад

LCSC and JLCPCB are sister companies. When you order a PCB from them with BOM (bill of materials) soldered, it sources the parts from LCSC. 100% reliable.

@Chupacabras222 27 дней назад

If they cost a fraction of price of reputable distributor, than it is 99% fake. My own experience. I burnt my fingers several times, and I no longer buy chips nor mosfets from aliexpress. Never again. In comparison LCSC is a reliable source.

@chaosflower4892 27 дней назад

If it doesn't come from RS, Mouser Farnell etc it will likely be fake. It if comes from ebay, amazon, alieexpress etc it will be fake.

@CXensation 27 дней назад

So the proof that it is a quality component is the unit price ? 🤣🤣

@Chupacabras222 27 дней назад

@@CXensation Not exactly. Most important is the reputation of the source.

@CXensation 27 дней назад

@@Chupacabras222 Yeah - I know - like spare parts for cars - only the reputed branded marked parts works. Rest is junk.

@LearnElectronicsRepair 26 дней назад

@@CXensation Give LCSC a try. Detlef put me on to them and he swears by them, the price of the components was much less than Mouser or DigiKey, in fact they didn't cost me any more than the fake ones I got form AliExpress, though the postage was bit more as they used Fedex but having said that it wasnt' expensive and it was quicker too. www.lcsc.com/ If you used EasyEDA and source your BOM automatically through that, then you are connecting to LCSC for your components.

@Manticore1960 27 дней назад

Datasheet shows that the gate threshold voltage should be 2v to 4v. I haven't heard of LCSC before. I'll add them to my favourites.

@LearnElectronicsRepair 26 дней назад

Detlef put me on to LCSC he highly rates them and the prices are very competitive, much less than DigiKey or Mouser in this instance.

@LarixusSnydes 26 дней назад

@@LearnElectronicsRepair True and they are the main supplier of JLCPCB. They would be quite daft to risk that position by cheating the customers.

@TheElectronicDilettante 26 дней назад

To test transformer, remove from board. Hook up a function generator to primary and scope to secondary, tertiary, etc. Also, you mentioned not knowing the frequency at which the Mosfets should be operating. All be it crude, the resonant frequency of the primary and secondary windings can be characterized using a function generator and scope, easily. If I can figure it out, anyone can. I learned how to do it by trying to match resonance of the primary and secondary coils of a Tesla Coil(slayer exciter, really) that I’m perpetually building.

@Turco949 23 дня назад

Thank you so much for this, sir! For a beginner like myself, this was very informative. Cheers!

@dunk_law 26 дней назад

Vgs varies between 2V & 3V nominally dependant on manufacturer & suffix.

@mattsan70 26 дней назад

Consider shorted transformer windings when this happens. Use a DIM BULB to test if all ok will barely light up. Those Active speakers are common for transformers to short out

@TheElectronicDilettante 25 дней назад

Sorry, last thought. The Vgs(th) of the mosfet is with in the range printed in a datasheet I’ve been using to follow along from Vishay. That MOSFET has an Rds(on) of 0.27Ω @ 10v. Did you try measuring the gate voltage when it’s powered on? The way the datasheet reads is that if a minimum of 10v isn’t supplied to the gate, it will never reach the low resistance state and will probably overheat or at least fail down the road due to overt thermal stress. Thanks for the videos. Cheers.

@LearnElectronicsRepair 25 дней назад

I didn't but I think it would be a good idea to try some of these ideas on the live stream Sunday 5pm UK time 🙂

@danblankenship5744 26 дней назад

The Vishay datasheet says the VGS(th is 2-4VDC. The AliExpress transistors are below that threshold.

@1kreature 26 дней назад

You need a curve-tracer or similar so we can see the full difference between these mosfets. Creating a Rds curve vs current or Vgs would be interesting. Breakdown voltage is probably wildly off as well.

@warwickbunn1250 26 дней назад

Do you know of any curve tracer testers available ? I have seen a hugely expensive and physically large old machine on the @MenditMark ? channel and I believe the next model up from Richards Peak Atlas DCA55, the DCA75, does via a computer. But I'm not totally sure about that.

@1kreature 26 дней назад

@@warwickbunn1250 I remember a video by IMSAI Guy a while back using a oscilloscope with a bit of external circuitry. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-nj8BGkA80ZU.html

@1kreature 26 дней назад

I think I've seen multiple kits for this on Ebay and Amazon as well. Should be the cheapest and fastest route for something basic.

@mikeb6185 7 дней назад

@@warwickbunn1250I have the DCA75 and it does indeed allow curve tracing via the supplied software - on PC only

@Andrew-rc3vh 5 дней назад

You can't just assume if the drive is OK then it will work. The circuit uses inductors that can break down at high voltage , or another suspect thing with a power supply like that is dodgy capacitors. Because of the nature of how it works it make sit difficult to test. It's times like this it is great if you ever have an identical board for spares you can swap components. Test by substitution.

@Pelican_t 27 дней назад

Useful Tip: Salvaging from E-Waste electronics gives you a higher chance to obtain a genuine component but may come with the risk that salvaged components can be damaged (mainly capacitors in my experience).

@LearnElectronicsRepair 26 дней назад

Yeah I agree

@user-kr8tp3ko8z 27 дней назад

you can probably review or make a transformer ring tester, which can measure for shorted turns

@LearnElectronicsRepair 26 дней назад

Already did that DIY ring tester : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0-LrAW6PpKk.html How To Find Shorted Turns Without A Ring Tester : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ndkrHqTZpwA.html I didnt' say it isn't possible to test for shorted turns, just that it isn't easy to do it. Firstly you need to unsolder the transformer, or otherwise disconbect everything from it. A lot of viewers would struggle to do that without damaging the PCB either due to the lack of the correct equipment or the lack of soldering experience. Even then, with a ring tester or the other method I described in the above video, you may not always get a conclusive result without another good transformer to compare to. So I stand by my original statement, it is not easy to diagnose that type of fault.

@romancharak3675 23 дня назад

After getting burned many years ago by buying components from Ebay, I only EVER buy components from reputable Parts Houses. It is definitely worth the price difference to have peace of mind, and a good result in my DIY circuits.

@TheEmbeddedHobbyist 19 дней назад

If repairs are for a customer then I only use components from a distributor like Rs, Farnell, and CPC. Other distributors may be available 😂😢. And pass the cost on, full transparency and more likely to be the correct part. But I have seen unopened packages being x-rayed as a main distributor had supplied chips with no silicon inside before. It was better to pay for the test than fit a 500+ bag and find it don't work. Even 40 years ago I could not fit components from RS or Farnell as they lacked the traceability, we needed full traceability back to the batch being made at the factory. So if fault develops we can recall all units that have parts fitted from the same batch number. Which was one reason we charged so much for our avionics equipment

@k7iq 13 дней назад

Try cracking open one of each of these FETs to see if there is a big difference in DIE size ? I use a big pair of wire cutters for D-Squared PAKs but that might also work with TO-247s

@TYGAMatt 27 дней назад

I never buy the cheapest parts from Aliexpress. And so far I've had a very good success rate. Or at least let's say that the parts have been reliable for the application I'm using them in

@LearnElectronicsRepair 26 дней назад

Mostly I have no problems with parts from AliExpress, I use them all the time. But in this case I was obviously supplied components that were 'not right'. But I think in future for power Mosfets in SMPS and output Transistors / Mosfets for PA amplifiers I'm gonna stick with LCSC or another more reputable supplier. They didn't even cost me anymore than AliExpress, only the postage wasa bit more expensive.

@winlose3073 27 дней назад

That is a very good example showing why working with preassumtions can make you fail no matter how much experience you have, interesting case!

@midgoog2 24 дня назад

The data sheet for the Mosfets shows the Gate threshold as 2 - 4 V. The tester shows the cheaper ones to be 1.8 V. Therefore the cheap Mosfets may have been production rejects that are close to spec but possibly useable in some circuits rather than being outright fakes. How they got from supposedly the reject bin into the reseller's hands points out flawed quality and stock control systems at the manufacturer. Obviously it is better to source components from sellers like Mouser, RS, LCSC, etc but for some of us the cost of shipping is often 5 times the cost of the parts themselves and the shipping delay is similar to Ali Express and Ebay. So we'll take the gamble and go with the cheaper option. Cheers Eric

@mehow357 24 дня назад

😂 So, it seems you are lacking knowledge about fake ICs from China. They do not give you underspec ICs from that manufacturer, they'll give you whatever they have and fake the engagement (incl. logo). In most cases, it's just some cheap version from different manufacturer, with different spec. but also quite often it happens you will get totally different, cheap IC. There are plenty of stories and videos on YT about that, you can check it out.

@watchmakerful 26 дней назад

Check also the gate capacitance, it must perfectly (+/- 5..10%) match the datasheet. If the capacitance is way lower, the transistor is fake.

@jmialtacct 22 дня назад

Never ordered mosfets from A, but I did order some BD140s. They eagerly broke down at Vce around 50V (must be >80V). Test failed. Also had LM358s - already the slowest opamp on the market - that were a whole order of magnitude slower than the norm, somewhere around 200kHz unity gain frequency. But on the other side, other certified fake audio ICs like UPC1237 and LM391x, performed flawlessly even at the max Vce.

@ivolol 27 дней назад

You might be able to use a milliohm meter to check their DS resistance while the gate is turned on With fake mosfets (or even just 'different' ones) the parasitic capacitances might all be different so they need different tunings to have clean turn on/offs... and without that they generate a nice bit of heat

@LearnElectronicsRepair 26 дней назад

I have three of the fake ones left, if anyone isinterested we can play with them on the 'Learn Electronics Repair and Friends' livestream this coming Saunday 25th August 5pm UK time

@stevejagger8602 27 дней назад

The only way to partly check for fake components is to use a manufacturer's specification to compare what you can measure with the component analyser. I have little trust in apparently low cost sources like eBay and Ali express. It may cost more to use RS Components, or Mouser or similar but you have traceability. Traceablity is what I had to follow when I worked as a registered electrician in the UK. If there is an issue subsequent to an installation or repair to an installation you have to be able to show that you used verifiable components in the installation. So buying something from a boot sale or a friend or eBay or Ali express is no longer verifiable. There is some point to regulation - like it or not.

@LearnElectronicsRepair 26 дней назад

Yeah I get what you are saying. Interestingly the components I ordered from LCSC didn't cost anything more than the ones from AliExpress! The postage was a little more.

@318ishonk 26 дней назад

Interesting indeed. Thanks for sharing! Also confirms me in my recent choice to buy a similar symmetric SMPS from Hypex, not aliexpress.

@DadofScience 26 дней назад

I buy my experimental and high-risk project parts from AliExpress but for repair work I try and source everything from a reputable suppliers unless there is no other option. For example, HDMI ports for consoles are only available from Chinese sellers.

@AstrosElectronicsLab 8 дней назад

Yep! Common problem with most Toshiba, Motorola, Hitachi, etc. transistors from China, all fake, all blow up. The obsolete 2SA/2SC ones? Good luck finding genuine. This is what makes trying to repair older amplifiers, etc. harder.

@BrianSmith-ow9gy 15 дней назад

Hi Rich You don't seem to use the little T7 component testers anymore, reverting to using your Peak device. Have you given up with the other testers? I watched your vid where you looked at the T7 and it seemed to conclude that they were pretty accurate and OK to rely on. Have you had a change of heart? I sort of hoped I could avoid having to buy both a Peak tester and an MSR unit and the capacitance tester (with the yellow bits) you use for quickly testing capacitors as well. One pays for 3 sort of thing.

@sirnukesalot24 20 дней назад

Is there a way to compare gate capacitance? The fake ones might be staying on so long that the switching overlaps. The fakes can probably still be used individually to drive a single power circuit.

@LimbaZero 25 дней назад

in old days we used 40W or 60W lamp for "protection" if there is short then it keeps glowing and not blowing components up. if it works then it should turn off. Edit: Maybe buy breakdown voltage tester. nice way to verify max Vce or Vds. Test current is usually adjustable with 0.2 mA to 3.8mA.

@LearnElectronicsRepair 24 дня назад

Thanks for the suggestion

@SkippiiKai 11 дней назад

@@LearnElectronicsRepair or show us how to build one. I mean, I'm pretty sure I could design one in half an hour from salvaged parts, and a 317,but I'm also sure yours would be better.

@zedcarr6128 26 дней назад

Here's my two penn'orth. There are a few designs online for Ring Testers, used for testing shorted turns in SMPSU transformers and LOPT's. Might make a good project video. Do the MOSFETS have to be closely matched? Could the failure be because the MOSFETS fitted weren't matched? After repairing the PSU, I'd put it on a soak test at 50% to 75% load for, say, 24 hours to make sure it's not going to fail, and destroy what it's connected to.

@LearnElectronicsRepair 26 дней назад

On average the MOSFETs are passing the same current, and being subjected to the same voltage at the same frequency. But the transformer coil may behave differently on the 'charge' and 'discharge' cycles so the V/I curve may be different. They are not acting in series or parallel with each other, as they are never both turned on at the same time, so I would not expect they need to be matched in the normal sense of that term. I think this conclusion is supported by the fact that High Side and Low Side Mosfets in GPU/Motherboard VRM circuits, which operate on a similar principle, often have different type (and quantity of) MOSFETs on the high side and low side. Regards Ring Tester, you may enjoy the following videos 😉 DIY ring tester : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0-LrAW6PpKk.html How To Find Shorted Turns Without A Ring Tester : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ndkrHqTZpwA.html

@julescircuits845 24 дня назад

I got burned by a batch of the exact ones you got from ali... bang goes the psu! Never again!!

@CTCTraining1 27 дней назад

The eternal problem of finding reliable and trustworthy suppliers in a changing world. I’m guessing AE don’t allow you to add video links into your product review for the dodgy mosfets. Keep up the great work 😀👍

@LearnElectronicsRepair 26 дней назад

AliExpress has no veto on that. Here is the listing I ordered from, and this is not a review, I bought them myself www.aliexpress.com/item/1005006139367287.html

@CTCTraining1 26 дней назад

@@LearnElectronicsRepair ... Sorry, I wasn't clear. I would be good to link from your product feedback on AE over to your video. I never doubted you purchased them legitimately 🙂👍

@LearnElectronicsRepair 26 дней назад

Ohhhh, I see what you mean 👹

@yannis92preloude 14 дней назад

All depends from which seller of AliExpress you bought the mosfets I have bought quite a few mosfets some are fakes and some are absolutely perfect all depends what the usage of them going to be. Especially in power supplies where you require extremely high current.

@gadgetmind 23 дня назад

I just got some K13A60D MOSFETs from Aliepxress and my cheap GM328 tested shows RDS of over 20hms versus datsheet value of 0.33ohms. Oops! Vth looks about right but that on resistance would doom them in many applications.

@ethanclement9647 27 дней назад

One more comment. Make sure the small electrolytics on the high voltage side are all up to specifications. Recently I repaired an amplifier where one small capacitor failed and caused new end of mischief.

@LearnElectronicsRepair 26 дней назад

You mean the ones you find in ATX type PSU in the base drive to the Switching transistors, driven by a small transformer similar to the one in the PSU design?

@ethanclement9647 26 дней назад

Just that in general, small things will make big differences, especially if the RC Time delay is reduced. Should one of those be out of spec.

@stevenbliss989 27 дней назад

Measure the Rds using 1Amp CC current and a multimeter. A technique you already know from your short circuit test probes thingy! :) In fact you could use that to do this...! :) :)

@LearnElectronicsRepair 26 дней назад

Let's try this on the live stream this coming Sunday 🙂

@FantaBH 22 дня назад

For me, it’s really frustrating to see all these videos about fake electronic components from AliExpress or eBay. I’ve been in the electronics repair business for over 35 years, and I’ve ordered countless parts from these sources. I've never encountered issues with fakes or anything like that; I’m not sure why or how, but for me, they’ve always been reliable. On top of that, it’s usually quite easy to get a refund if you do end up with counterfeit parts. It’s important to remember that nearly every electronic component is manufactured in China and it is a mass production so must be cheap much cheaper then anywhere else. I used to source components from Tayda Electronics, a shop in Taiwan near the factory. They were much cheaper, significantly more affordable than eBay or AliExpress, and they used a very fast Singapore postal service that was reasonably priced. However, since the Covid pandemic, they switched to DHL and never went back to Singapore Post. Now, I only order from them if I need more than just a few pieces

@zcomputerwiz 20 дней назад

What exactly is your point? This is a very well known and well documented issue ( fakes ). Good for you that you've not had a failure, but your anecdotal experience doesn't change that.

@FantaBH 15 дней назад

@@zcomputerwiz My point is that I’ve never encountered issues with fake components-whether it’s transistors, ICs, or electrolytic capacitors. I’ve never had a problem with any of them. The only exception was once when I ordered 10 triacs from Banggood, and they all turned out to be thyristors instead of triacs. I’ve seen many videos discussing fakes from eBay or AliExpress, but wonder how I’ve managed to avoid this issue with a few hundred orders from those sources over a few years.

@dcocz3908 26 дней назад

So I've heard of fakes from Aliexpress and EBay before. Kind of hit and miss. I did see something funny recently, Aliexpress sell bags of loose SMD resistors and capacitors. Essentially they are collected from Chinese SMD/SMT lines, under pick and place machines etc. I'd hate to sort through them just to find the one component I needed since they are all random

@dugannagud6254 17 дней назад

Always good videos.

@Tims_Projects 26 дней назад

Fake? or "Seconds" For those that don't know what a "Second" is. Something that works, But not to the specification it should. Back in the 60's my mother would go to the Big clothing departments to by me some jeans. the brand name ones where very expensive. But the shop also sold "Seconds" these where the same as the branded ones, but had a slight defect, but where half the price. If you just want to switch on a light bulb, the cheap MOSFET will probably do?

@budgiefish 26 дней назад

Would bringing up slowly on variac whilst monitoring power levels highlight shorted turns on the transformer and/or limit the risk of blowing mosfets (e.g. gate drive problem, not the fact that the Vgs(th) was stupidly lower in the fakes)? Whilst it wouldn't stop something going pop if dependent on being at full voltage, it may allow you to see the problem beginning to occur before it actually does, if you follow me? :)

@BigBoss-rh7zq 26 дней назад

I bought metal cutting tools described like original on AliExpress and they are so fake that cannot be used not even for wood.

@x5-acousticguitarstuff.2 12 дней назад

Can you please advise me on where I can get 2 x original or Non-Fake STK-8050 Power Amplifier Modules. OR could you make a Video on how to REBUILD these Chips with discrete Transistors and Diodes.

@rodrigoetoobe2536 27 дней назад

where we can get these two videos you mentioned? 1:01 and the reverse eng of that psu video

@andymouse 26 дней назад

Just go to 'videos' on his channel page.

@LearnElectronicsRepair 26 дней назад

Sorry, that was my bad, I've now updated the video description with the links I mentioned

@warwickbunn1250 26 дней назад

Brilliant Brilliant Brilliant If you hadn't got those, substandard 😉😅, mosfets you wouldn't have needed to go through drawing out the workings again and your various possible causes and methods of testing. But because you did I now know so much more and with your excellent drawings I now understand the shorted turn issue so much better.😊 So, bad parts are not good for fixing stuff, but great for this channel as they are so good to learn from 😁 What a dilemma 😅

@Rocco_v 26 дней назад

Look at the back side of the fake mosfet at (20:50) The shape of the metal is different than a real mosfet. I have received some of those on ebay and they were all fake. A true International Rectifier mosfet has just a rectangular metal part on the back side.

@tonydickerson999 23 дня назад

Does the datasheet for the MOSFET give the correct voltage

@retiredjan4714 26 дней назад

The *whole* point is: when you replace a part make sure the specs are the same.! Different manufactors have ,little?, different specs for the same part number. Even the same manufactor can have different spec based by a change in manufactoring.

@RexxSchneider 24 дня назад

The range for gate threshold voltage can be quite wide so samples from the same manufacturer can be quite different, but I checked both Vishay's and International Rectifier's datasheets and they both give 2.0V - 4.0V. The mosfets from Ali Express might be manufacturer's rejects as they are out of spec. Unfortunately that means that all of the specs then become suspect, so you have to test every other spec that's important for your application (breakdown voltage, Rds, gate charge), otherwise you can't safely use them.

@norbertsmallegange6331 23 дня назад

And how about the gate capacitance?

@weerobot 26 дней назад

17:09 Checks Mosfets...

@dinf8940 27 дней назад

problem with chinese clones is they almost exclusively use vdmos/ldmos so its impossible to match all characteristics of prehistoric technology like hexfet. in many cases they work fine and often greatly exceed specifications - unless your design relies on some inherent limitation to work

@Amplified208 27 дней назад

Wow, I can't believe the difference in the gate voltage. So do you know off hand know what part number they actually are ?🤔

@ivolol 27 дней назад

Could be any of 100 different models that OEMs produce with a Vgs under, say, 2.5V You'd need to measure quite a few more practical parameters to start narrowing it down

@LarixusSnydes 27 дней назад

Hard to tell really. It's not only the gate threshold voltage that defines them as a particular type. There are many other parameters that all need to be tested before you can narrow down what you really have, like switching speed ( both on and off ), V(DS) breakdown voltage and so on. You also have to keep in account that they might not be functioning properly either as their original designation. They might very well be rejects from the production lines.

@Amplified208 27 дней назад

@LarixusSnydes yeah I figured much more testing of the MOSFET would be needed. Sad to see fakes 😔

@LarixusSnydes 26 дней назад

@@Amplified208 Sad indeed. So many shops using AliExpress. Hard to shame all the dodgy shops out of existence.

@WallaceRoseVincent 21 день назад

What if uou crack open the cheap mosfet and the good mosfet? Did you see what exactly was bad about the less expensive chip design?

@pauldery7875 27 дней назад

I've seen this on other videos, so I'll never buy these high powered mosfets from ali express, thanks for sharing. Paul USA!

@Dutch_off_grid_homesteading 26 дней назад

Heya, oh wouw just because the gate treashold of the mosfets is a differant voltische they blow up. maybe mosfets and other semiconductors ordering them not on ali any more.

@gorjy9610 27 дней назад

With AE you never, absolutely never buy any kind of semiconductors from cheapest seller. There are some good stores but their prices will always be at least double what cheapest one asking for. They'll still be much cheaper than western stores.

@professormack 21 день назад

The components ordered from China have never caused any problems. You have to read the feedback. There are many reliable sellers. Many followers above 96% rating many sales. 7 days delivery. It gets here faster than if I order from the corner store.

@thulinp 26 дней назад

There are absolutely a lot of fakes and pulled, used semiconductors on Ali. Best case it's reconditioned used (they look new). Sometimes they recondition the print too. Sometimes they print a different model on it. Some are new rejects, found in the dumpster of the semiconductor factory. They just don't care, as long as it sells. Fake reviews fix the review issue they invariably cause.

@davidhollfelder9940 27 дней назад

On the xfmr, maybe try testing with a ring tester?

@LearnElectronicsRepair 26 дней назад

Agreed but you have all the hassle of desoldering the transformer and then without a good one to compare with sometimes even that is inconclusive.

@tinkerman9525 22 дня назад

Best to test the RDS(ON). Most FET and transistors are fake. Especially power transistors. For them check the gain is in spec. Got some 2n3055 with gain close to 100😅😅😅😅😅

@Aviopic 26 дней назад

It's just as much a design fault, nominal threshold is 3V with a minimum of 2 and a max of 4V. Now 1.8V is a bit below the minimum specified threshold but a design should be robust enough to handle. Somebody in the design office didn't check the datasheet.

@viniciusvbf22 26 дней назад

LOL. Looking at LCSC product list, I found this category "Cleaning/daily necessities (2,715)" with some very interesting product groups 🤣 Other car Interior Accessories (9) Other brackets (16) Umbrella bucket (1) sleeping bag (2) Sticky dust pads (24) vacuum cleaner (233) Umbrella bags (1) wardrobe (11) Other cleaning supplies (226) SoleCleaningMachine (10) Wipe paper (134) trash can (216) Storage (83) Towels and bath towels (57) stools (40) Garbage bags (186) ashtray (5) Daily entertainment (11) CarWashingMachine (50) Bedding (3)

@Mcfreddo 26 дней назад

I've learnt something important! (Thanks)

@Dutch-linux 27 дней назад

Like i said many times watch out for fakes.... now even by the wel known suppliers there can be fakes... and of the why people would do such a thing ??? who knows they sure don't make any money from it... it does make working with electronics more dangerous tho!!!

@jonnyduncan7056 27 дней назад

Surely an insulation/resistance tester (Megger) would show up if you tested the Transformer?

@capriracer351 26 дней назад

Only if one of the turns is shorted to ground. If a turn is shorted to another turn, it will show up with a ring tester, or maybe a very sensitive milliohmeter. A ring tester will give definitive results though.

@ellensburgamplifier 27 дней назад

"They" the trolls who sell on Aliexpress, have been getting better over the years at faking components or producing fake components that are no longer in production. One also has to pay attention to what they are getting through LCSC as they carry several different manufacturers of the same part.

@izzzzzz6 27 дней назад

Check the voltage difference of the two main caps. if one is going bad the switching will be out of balance. You might be able to test for shorted transformer turns with a VNA. If you knew how many turns and roughly the length. Or perhaps if you compare the reflected signal from either end. A VNA is usually used in radio antenna / coax setups but you can find the length of a piece of wire with it. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lddb8UezWj0.html Perhaps this is better?: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-tX-V1pm0dWw.html

@johnmcdaniel3471 27 дней назад

Thanks!

@LearnElectronicsRepair 26 дней назад

Thank You for your support 🙂

@LearnElectronicsRepair 26 дней назад

Thank you very much for your support

@torstenb5248 27 дней назад

You can't trust any aliexpress seller. Same for ebay and Amazon. Maybe the parts are good enough. But you never know. Nort worth the trouble for money you "save"

@Shocker99 13 дней назад

It looks like at least half of what is sold on eBay and Amazon are drop sellers for items sourced from AliExpress. The images are often exactly the same with very similar descriptions.

@andrew_koala2974 27 дней назад

CORRECTED EDITED FORMATTED TEXT ; Sometimes one can replace faulty components in a switch mode PSU ; only to plug it in and watch the new parts self destruct. ; I recently experienced this problem with a power supply that blew ; up even though it was connected to a current limiter (light bulb). ; In the previous video I reverse engineered the PSU and eliminated ; just about every possible reason for it to fail again. ; What I was left with were either fake Replacement MOSFETs or a ; couple of difficult to test fault conditions.

@davidt6903 26 дней назад

Hello Richard is there a way to Email you? I would like to ask some questions without the whole world being involved.

@firsteerr 26 дней назад

i test EVERY component with a cheap tester , it might not be 100% accurate but you can tell poo from good

@darrenmurphy6251 25 дней назад

i bought some definatelly fake irfp460 from ebay ,they have grinding marks and missing indents and solder tinned leads so defo fake but i have a hv leakage tester so curiously tested the vds breakdown voltage of a few and to my shock at 500v (spec) they still hold on till 512-520v before any significant leakage current ! wtf ! that should be a complete fail next test would be rds on or gate capacitance or destructive test ptot but i know theyre fake so not going to bother but bizzare they achieve the 500v rating

@SS-mj2mq 26 дней назад

Just ask for papers of authentic! And they don't offer any papers I wouldn't bother. But if they do offer papers and they fell you can get your money back. 👍💯

@paradiselost9946 26 дней назад

whereas our laws are different and we get our money back without no papers... so we tend to NOT get fakes...

@SS-mj2mq 26 дней назад

@@paradiselost9946 well that is awesome area is different.

@MartinPiper6502 27 дней назад

I don't trust AliExpress for anything.

@Lightrunner. 27 дней назад

The bill comes fast and ever🤣. Warrantys

@LearnElectronicsRepair 26 дней назад

To be honest most components I order from AliExpress are just fine, but I'm thinking in future I'll use another supplier for power mosfets in SMPS and Auio Amplifiers. LCSC weren't even any more expensive than the fake ones from AliExpress, only the postage was a bit more as they used Fedex but then they were also quicker than normal post.

@Sydney268 26 дней назад

Was always amazed at your blind faith in aliexpress components, in my experience 99% of the time they're either fake, used faulty or rejects, especially if the items are not available from a reputable seller.

@LearnElectronicsRepair 26 дней назад

Mostly I find the opposite - when I think how many times I buy components from AliExpress and how often I have any problem with them - I can only think of two occasions than happened in the last year