Відео

mean get 4 views

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An atmega 328 can easily generate frequencies above > 100khz even a few Mhz using direct port writes

I think you guys might be missing something? 1. A component tester only has Capacitance as a bonus feature and if you want a proper reading of capacitance use a high quality LCR meter. Even most Multi-meters don't read capacitance accurately. Reason being an LCR meter uses an entirely different way to measure, most use a bridge. 2. I have both an expensive LCR meter and that Der EE version and I can tell you the Der EE one also lacks accuracy so I don't necessarily trust it either. So use a component tester for Transistors and Diodes etc. Use a multi-meter for Resistance, voltage and current and use an LCR meter for inductors and capacitors and life will be good. P.S. If you want a proper component tester buy an Atlas component tester, it is made in the UK and runs rings around any of those Chinese things. It will even show charts and readings on a PC screen.

Good rule of thumb: it's usually the electrolytic capacitor. They are a major point of failure.

Now you need a reverse version so you can work on the back of the card if needed 😅

Possibly the capacitor has constant current in it and is always charged. that would have explained its short life.

Everyone buys in China, just few do better testing before buying. Don't ask how I now.

The X2 capacitor will fail some day, it can take many years. This type of capacitor is not designed to carry current. I talked to a capacitor manufacturer and he said X2 capacitors are only designed to last 8 months to get them thru EMI testing. I see a lot of engineers use X2 capacitors to make it easier to get thru UL and because they just don't know. Across the line capacitors are designed to fail safely by clearing any fault. Eventually there is nothing left to conduct. Resistors in series also fail internally from surges opening up resistive paths. This is very common with carbon film resistors and have replaced a lot of them in capacitive dropping circuits. They will never look burnt, just open.

Tldr: zener cooked main smoothing cap end of the story Total classic of failure You could wire the cap with wires away from it to save it from the heat Even a good caps are rated maybe at max to like 10k hours under 70-90c

Great video, I like the dual camera set-up. As others have said, it's a capacitive dropper - a cheap way to drop a large AC voltage at a very small amount of current. Inductors are expensive. Keep learning and taking us along for the ride, subscribed

Search for " microchip AN954 Transformerless Power Supplies " - it's an application note from Microchip that shows a few ways of making such power supplies and includes some formulas.... it's quite common to see such designs. There are modern high voltage linear regulators like microchip LR4 or LR645 but these old circuits are cheaper and I have a feeling there's little interest, as some companies do it on purpose to get service calls after a couple years of use.

When replacing capacitors that have died due to high thermals over time, it's useful to leave them long-leaded and space them away from the PCB as far as reasonable. I'm not surprised the zeners are toasty all the time, even when the switch isn't thrown, classic capacitive-dropper zener topology really.

Cool fix. My thoughts: 1. Capacitive droppers (already explained by HwAoRrDk) are generally okay (for low power stuff), but they're not very efficient and don't provide galvanic isolation, so everything has to be in a double-isolated enclosure. 2. Another failure modes of those power supplies is the dropper capacitor itself. These X/Y rated caps are the "self-healing" type. If there's an over-voltage on the mains (e.g. nearby lightning strike, or surges from the transformer station switching lines) it can cause arcing inside the cap, creating a short. But these caps are designed so that the short burns itself out and the cap keeps functioning. But obviously, the burned area is no longer available for storing an electric charge, so the overall capacitance drops slightly. If that happens often enough, eventually the capacitance will drop to a point where the cap can no longer provide enough current for the circuit. I had this problem with a remote controlled ceiling fan. The control board used a cap dropper, and every time I turned the fan on, it would reset. Turned out the dropper cap had gone from 100nF to about 10nF and had to be replaced. I know this wasn't the issue here but I think it's worth keeping in mind. 2. With just 50 or 60 Hz mains, you can often measure the ripple using your multi-meter in AC mode. 3. This thing is powered all the time, right? And it probably isn't super efficient. You might want to measure the quiescent power draw, and cross-reference with your electricity bill to see if it's worth keeping around. That fan I mentioned above? It turned out it cost me 50€ (~42£) per year, just for literally hanging around. A better quality unit with proper low standby power might pay for itself within a few years.

My sympathy to the relay contacts under this fault condition..

very nice video. thanks for the contents. I am reaching to this conclusion that Capacitors are bad :D

I have recently had exactly the same problem with mine. The only difference is that I also needed to replace the zener diode. I had previously replaced the X2 capacitor a few years ago, as its capacitance had dropped significantly.

It's surprising to see how few components are actually needed to make a circuit like this function. Also if you were to try and repair one of these at home, you'd now have a good idea of what to replace.

Thumbs up for doing sketchy testing methods. 😂

In the UK when a relay does what you describe we say it’s chattering.

The neutral appears to be going through the film cap, so it could be using a capacitive dropper to lower the voltage across the actual circuit, film caps can go bad too and lose capacity.

The IC is probably a microcontroller, there's not much to say except that the analysis was very didactic. In Chinese devices, you should always be wary of electrolytic capacitors. The average lifespan is about 5 years, but when they were manufactured in the USA, Japan, European countries, etc., they lasted decades. As for resistors, I worked for a year assembling boards in the 80s. Up to 4 colors (digit, digit, multiplier, tolerance) I knew the value as soon as I saw them, for more color bands it was a mess.

The capacitor has capacitive reactance, the reactance is 1over 2xPixFxC the result is in Ohms. en.wikipedia.org/wiki/Electrical_reactance

We can clearly see that you don't know anything about capacitive psu. Please don't do this kind of videos, you are guessing things...

Oh no i broke the 404 views! Anyways its always frustrating when stuff is engineered to fail. I am not a pro at Circuit design but even i would have made it better and would have made it so it does not fail in the stupidest way. Although hinted by the capacitive dropper and instead of a 5/3.3v regulator they use a zener, its probably quite cheaply produced. And most low power circuits have capacitive droppers cause it works fine for low power devices, and those 'cheap ubiquitous unmarked chinese padauk style, pic clone microcontrollers ' how bigclive identifies them i believe, dont draw much power at all and they are dirt cheap like a few cents and usually mass produced and unlabeled and one time programmable/maskrom so they cant be reprogrammed The relay turning of is a problem some people have with the cheap smartplugs that also use a capacitive dropper although most use a regulator ic instead of a zener dropper for the mcu voltage. Dodgy capacitors... I replaced tons of them in my smart plugs and they are all happy and working again These cheap mcus usually have a uvlo (under voltage lockout) or a brownout detection that resets the ic when unstable voltage is fed in to prevent it from crashing or locking upor doing weird things it is not supposed to like skipping instructions. This is a known vulnerability that some hardware hackers exploit to skip instructions and to basically get the ic to skip critical security code and to give them full access to it

I have a feeling Chinese electronic components quality in 2020's is like the quality of Chinese cars in the 1990's. Specially capacitors inside cheap electronics. So far, and after watching so many repair videos, the no.1 failed component is a Chinese made capacitor. :( Please don't get me wrong, Chinese factories build component to a price. If you want a Chinese capacitor with quality similar or close to a Rubicon one, you can find, but not in the cheap electronics that floods Amazon and other markets.

It's not the 1M resistor dropping the voltage or limiting current - it's the blue X2 capacitor. This kind of circuit is called a capacitive dropper. It works based on the dynamic impedance of the capacitor to AC. The value of the capacitor (probably some hundreds nF) dictates the output voltage and maximum current. The 1M resistor is just a bleeder for the cap's stored charge so you don't get zapped touching the mains input terminals even after unplugging. Funny you should mention Big Clive as he frequently covers these kind of circuits.

Hi Tony. Interesting circuit today. There's a lot to be said for drawing out a schematic like Clive does. It's a great learning / teaching ade. So you've had a Win with this one.👍😎

nice, but the logic has a fuse?

well, the capacitor is -40+105 degrees which is 65, so...the manufacturer was correct :) (joke)

The majority of products available are trash you will be surprised the number of times AliExpress are better than what you have locally 😹

Most producers would tell You, that this is perfect design when device fail right after warranty period. This looks like aliexpress quality, but I saw a lot better power supply's there. If I'm not mistaken, currently EU demands, that device in standby need to draw less than 0.1W, so I guess that this constantly being hot would not fit in that description. Something shady, in my opinion, is going on here.

It is always a crapacitor!!!

Over the last few years I have had a few cases (water heater, Yamaha amplifier and several socket power meters) where a film capacitor from a transformerless power supply lost capacitance and was unable to supply enough current to the system. Often, the decrease in the capacitor's capacity causes the next element of the circuit - the resistor - to overheat. It is possible that this is not the case with this particular device, but I wonder if the capacitor has its original capacity. Quote of the Day: "Metallized polypropylene film capacitors are known to be one of the most common causes of failure in electronic systems"

if you make legs to the diode and made it flying, it will run more cold. Also you can change the diode for a stronger one, probably not smd but it will be capable to run more power through it. The capacitor can be moved using coated wires, since it is 24v and low current, it will prevent degradation by high temps.

I think, it's atransformer less power supply which contains x capacitor , resistor and bridge rectifier used only in low power

The "NO/YES" fully reads "R12 NO 2H" vs. "R12 YES 4H", so presumably you can adjust the timer with that resistor.

How much power is this wasting when the towel radiator is off. With that zener at 95+ degrees C all the time, it must be wasting several watts. What a crappy design. I would modify it so when the relay switches off, the whole thing switches off. You could have another push button to turn it on.

Amazing job mate. Hope this video encourage people to repair appliances, as maintenance companies try to scalp you on every occasion. Also about the value of not producing more e-waste that could work again. BTW, I just saved my boiler main board two months ago, as the maintenance company kindly offered a "reposition" from 350 quid while I spent 10 in components (a cap blown and killed "the" TOP244 AC/DC converter). Please, you all, try to fix your home stuff !!! Tony set the example here 😀

I have one of those cheap component testers like yours. It is absolutely the best eight bucks I ever spent. A magnificent device.

G'day Tony! Good to hear you laugh so much with Your "Contraption".😉😆 ISA is notoriously "noisy". PCI protocol was to address this issue, + others of course. That Ribbon Cable is terrible. If you have an Electronics store that you can walk into. Go there and look at their Rainbow Coloured Ribbon Cable, it usually has heavier/ better wire and is more Subtle to manipulate. Being able to handle it yourself in the store, you'll know straight away if it is better or not. Using that mains cable is a good choice, just keep in mind its rated at over 1,000 Watts. ISA ribbon cables usually have Ferrite Bars near each end. SCSI cables use a bar with a slot to thread the cable through, keeping the ribbon flat. Thats a great motherboard you have there. It has the upgrad socket. (I don't understand why my notifications are more than a week late?)

Thanks for trying but Is your method clean? Some times you start with the old tester, sometimes the new one, sometimes you discharge, mostly you don’t?

в электронике есть только 2 проблемы. есть контакт где его не должно быть. нет там где он должен быть. я честно не досмотрел до конца. но я прям уверен в том что проблема была в падении напряжения на проводнике. как насчёт дублирование контактов? ну к примеру SCSI там их много. на одну линию использовать 2 контакта? а ещё они помехоустойчивые. 80*3 дадут 240 контактов. 62 это 8 бит и 36 это 196 контактов... можно усилить землю и питание. а ещё они витые. подумайте.

neat!

Adding decoupling caps on the far PCB, as someone else already mentioned, seems like a good idea. Worst case, you won't need them and can leave the positions unpopulated (which won't hurt). And this is just me thinking out loud, but you could also try and replace the ribbon cables with ethernet cables. Each one gives you 8 connections, so you might have to add a bunch of them. But they're twisted pair and shielded, designed to carry much higher bandwidth signals. Since PoE is a thing, they can also handle some amount power. And both the cables and the connectors are cheap and ubiquitous components that can easily be sourced. Same idea, but fewer cables at a higher price would be bunch of USB-C cables.

Nice to see it came down to the usual 'crapacitor' & not the toasty looking Zener!

Thank you. A great video.

hi Tony, if you think about it no manufacturer ever puts power through the ribbon, everything in your PC has power cables.

Hey Tony I liked this one. Always better to keep something away from the landfill. It is certainly satisfying to know that many things can be repaired quite ‘easily’. congrats!