This is an excellent comments section and a well informed video too. I've just repaired my Panasonic microwave and worked through the circuit on the inverter to checl the components. Before the the inverter there is LC and MOV filtering with single glass fuse. Energy is switched with a spst relay on line. Safety interlocking shorts the line and neutral if the relay is closed, but the door opened (user exposed to rf). Idle current for the inverter (230volts ac) is
Well done for resisting the temptation to power up the switching power supply, you had me worried for a moment. The arcing out put from the iron transformer and numerical output from the catculator are a very good deterrent against dismantling my microwave.
Quite a while ago, MikesElectricStuff took a look inside an inverter microwave that got completely trashed by the bulb blowing. It blew a PCB trace when the bulb blew, and the arc flash from that trashed the logic circuitry effectively rendering the whole thing scrap. Sometimes simpler is better... I am surprised these inverter microwaves haven't taken over yet, switching PSUs have taken over nearly everywhere else
@@Alexelectricalengineering or maybe cheaper than a switching supply? I mean, nowadays the MOTs have the absolute minimum amount of metal in order to work. Nothing like what they used to make...
Well, the inverter side needs actual copper wire in the unit, while the iron transformer just uses CCA wire. It is a lot cheaper to stamp out iron laminates, and wind the CCA wire on formers, on machines long since paid for. Low cost materials, low cost labour, and as you ship by sea volumetric mass is the rate used, as a microwave oven is almost all air inside, even with a 2kg lump of steel in it. The inverter ones are only used where you are paying much more for more precise control, as they allow cycle by cycle PWM switching, so instead of the iron core having a PWM over a 30 second repetition period, you now have it based on the input mains frequency from the control panel, so the apparent power delivered seems to be much finer, as it is being adjusted either 100 or 120 times a second, per cycle power limiting.
And yes, even on a regular microwave that lamp blowing can take out the 10A ceramic fuse, I have changed many fuses along with the lamp, and modern ones now also use an 8A fuse in 230VAC countries, as it is cheaper, and include a soft start circuit to limit the inrush current into the transformer as it turns on into a cold filament of the magnetron, or with the duty cycle switch turning it off for a few seconds every half minute.
@@liam3284 The microwave fuse does that, though I have seen even 15W incandescent lamps trip a 63A main breaker when blowing. Lamp in a ceiling, with old 4mm wiring to it, so a really low impedance supply. Did not blow the replaceable wire fuse, though that could have been because some previous tenant had replaced the 5A fuse wire with 1.5mm copper wire doubled up, years before, so it would never blow, except for a dead short for 10 seconds.
now you know why the new ones do not last half as long, we replace 1 part with 100 parts, of which many have a lifetime of less then 1000 hours. we call this "progress".
Microwaves with these power supplies are inverter microwaves, which aren’t subject to the long-period on/off duty cycles to deliver partial power. In other words traditional microwaves with normal transformers run full-power for 5 seconds and then zero-power for 5 seconds, to provide 50% power. But microwaves with this kind of power supply do not have these long-period duty cycles to achieve partial power. So it actually is “progress” if you care about heating food more smoothly.
My guess is you could have a decent switching supply that would last the life of the microwave, as long as you don't skimp on decent parts and have sensible board design.
@@HobkinBoi I will say that in general the iron core transformer is generally really reliable. They do fail with shorted turns with the CCA wound ones, and a replacement is as expensive as a new microwave, so the good ones from scrapped units are pressed into service instead. I have scrapped more microwave ovens for the cavity rusting through where the turntable runs, and, for the recent few microwaves, the failure was the actual RF filter assembly on the magnetron arcing over internally, which is a really odd thing to have, as those are pretty much just a thick ceramic tube, with silver plate on the inside and outside, potted in hard resin. I guess they are using cheaper materials there, leading to the failure. Despite the high power it generates, the only failures in magnetrons is from the output probe arcing over from dirt in the waveguide cavity, from the mica or RF transparent plastic cover either breaking, or being dirty and burning up. Only ever had one fail due to age, but seeing as it was 30 years old, and went low output, it had definitely done well. Replaced with another used one, that was younger by around a quarter century, and in good condition, with the right fin and mount orientation. Also had one fail with a broken filament, but to be fair that oven had taken a trip off the table to the floor before that.
From reading up on prior literature and from what I can tell, the large inductor on the DC bus is used both as a current source for the resonant tank circuit and as interference suppression, the top IGBT is used as an active snubber with the 3.9uF capacitor, and the bottom IGBT drives the resonant tank circuit (formed by the 180nF capacitor and the transformer primary. similar to a single ended induction heater). I can dig up some of the patents and schematics that Panasonic devised for the inverter technology if anyone is interested.
For his schematic it was clear that it isn't a half-bridge, as he claimed. You confirmed my suspicions that it is resonant and that the upper IGBT is an active snubber. It is nearly impossible to achieve low leakage inductance with a transformer wound in that way, and that winding design is pretty much essential to for the voltages involved without running the cost way up. My guess is that the leakage inductance is used to advantage in the resonant circuit.
I salvaged a comparable board from a dead MO. I figured that these would help make the devices die earlier since any switching PSU has a much more limited lifetime than a good old passive transformer. However I figured it did have some benefits. The board had a PWM entry to smoothly reduce the power output. And that's nice because you don't have this with the regular transformer. Instead when you want 300W, it does 900W for 10 seconds, and 20 seconds pauses, which is a disaster for small pieces of food that you don't want to burn. It also alternates heating and cooling of the magnetron which certainly shortens its lifetime. So there are actually also some good points in having an electronic PSU instead of a transformer.
I wonder if they connect to the 2 sides of the heater to disable the doubler & prevent excessive voltage/arcing if the filament goes open or is disconnected
I've found basically the same power inverter like 7-8 years ago, when I was a kid. Don't remember much but transformer, heatsink, big resistor and HV diode look very familiar, I still have that 15W resistor and diode! Back then I didn't know much about this stuff and I wondered why 12V bulb barely lights up powered via a diode (large voltage drop), or why transistors "don't work" (they were dead-shorted, just like yours). Thanks for bringing back some memories
Yep, I tore apart a Panasonic microwave as a kid looking to tempt fate with some microwave oven transformer experiments and was disappointed when I was met with this style of board. Probably for the better that I wasn't able to mess with high voltage lol
Saw my first one in a restaurant (not rated nsf) health dept said dumpster it... lol I never saw the inverter work, stuck some guts from an old goldstar in it .... worked great! That was in 2009... 😊
To power it up, you connect the brown wire to ground, orange wire through a 10k resistor to ground, and feed a 220hz PWM (TTL, so 3.3v to 5v) square wave signal into the yellow wire. The duty cycle has to be below 43% when first powered on.
@andrew_koala2974 After 13 years teaching and 30 years in the military, I would be on the assumption that your life would have come to something better than flaming person on simple comment on a UA-cam video. I know life might have become harder for you after your daughter left you to go work in NYC, usually people can fall into a spiral of depression and sadness after they children have left them but for you I think it has led you to fall in a spiral of mental insanity. Previously one of your comments on one of your videos flames a simple comment voicing their opinion about the music choice, but no you had to attack that person for a simple missed correctly spelt word 'your' instead of using 'you are'. Many highly acclaimed people unlike yourself do not solely focus on ones spelling but the context and reasoning behind their comment. Around the UA-cam community uploading videos in 720p is not acceptable for viewing, 1080p is the standard in the community but yet after your 13 years of teaching English and History and 30 years in the military it would be assumed that you would understand the UA-cam Algorithm and see that uploading in 720p is not beneficial and almost every current phone can stream and most can even video in 1080p or even a higher resolution, so after your UA-cam videos in the past year don't even bring in an average of 30 views but your mentally insane brain can not comprehend that less than 30 views in not good performance. Any normal person would either give up or change the way they produce and upload their content but you brain does not understand that you should change your videos or give up. To Summarise you have passed the line between insane and normal. Flaming people's UA-cam comments is not acceptable or healthy for anyone. Go put close UA-cam and hide in Sydney, and leave all these peoples UA-cam comments alone.
There is other aspect of this power supply: Normally on a "700W" microwave the magnetron itself is a 1.4kW device, it is just because operating at half of the time makes the 700W of it. This supply powers the magnetron by all the time (I mean both mains halfwaves, neglecting the 100Hz), so it may really get the full 1.4kW out heating microwaves from it. Just reducing the current won't work, as it would cause severe degradation of the magnetron efficiency: The 2.4GHz AC amplitude inside needs to match the magnetron voltage to get the ideal efficiency (no excessive drop across the electron stream), wgile the total voltage can not be lower, as the electron speed has to match the resonant frequency of the cavity.
Ive salvaged many of these. They have some neat parts. I remove the primary and apply standard 5T + 5T and normal irfp250 zvs. Not ideal output for pretty arcs as ratio way too low, even with lower pri. Just high current ac that burns even aluminium immediately. I remove sec and rewrap with .3mm from the fan motor and drip on epoxy in process, can fit on 1500 turns easy, and makes a pretty resilient hv coil. Also make a big ferrite out of two matching transformers, and same for hv coil. Makes a pretty kick arse high current and hardwearing transformer. The mw's with the EE ferrite and secondary inside the primary have the best bobbins for the secondary, but not suitable ferrites. The mw's with the UU core are best for ferrites that can be mixed and matched. Seems about half are big, and about half slightly smaller, but only 2 sizes, no matter what mw they come from. Thats what i use them for anyway.
The doubler circuit is connected to the cathode in this special way to disable voltage doubling when the heater wire is broken. A magentron without heater but with high voltage could emit some other radiation.
It won't amit any other radiation. With a cold cathode, you have no current. Magnetrons do produce X-rays in normal operation, but 4 keV is too low energy to pass through the copper anode. Even a thin glass vacuum tube will block X-rays under 10 keV.
@@mernokimuvek You're right, I didn't think about the low keV, but magentrons can produce X-rays when the filament burns out but is still hot enough to emit some electrons. You will get a hotspot which will give you enough electrons for a accelerated path inside the tube. Once you disconnect it, it cools down and then will never generate anything again. Correct me if I'm wrong... I thought the beryllium stem of the antenna was quite 'translucent' for X-rays?
@@SunnyJulienDivine I tried disconnecting the heater and it stoppe emitting microwaves in a few seconds.(With the high voltage still connected). The beryllium oxide or aluminium oxide insulator is still a few mm thick. X-rays tubes with thin beryllium windows rarely emit under 7 keV.
Thanks dgw!! A great reminder to not bother playing around with the electronic transformer. I have 5 of them and another channel shows how to get it working but I have decided not too and as you say they are fragile to experiment with . Cheers
The 3 small wires (brown/orange/yellow) are PWM input for adjusting the power level and a feedback signal for the oven control (half of the PWM signal). both signals are using opto couplers. There exists also a smaller variant of this module with one IGBT and the DC capacitor has 3 µF and not 5 µF. This principle seems to have a small disadvantage: Reducing the output power will also reduce the voltage for the filament of the magnetron.
I gues the heater voltage doesn't vary that much, because the main load is the anode-cathode current, that doesn't affect the voltage drop much. The magnetron simply tends to drop about 4kV no matter the current. This clamps the transformer voltage per turn to a sort of constant value. The anode winding is probably between the primary and the heater winding for this reason. The anode winding is like a bi-directional zener on the heater winding :).
I just tore apart my first microwave magnetron, I used my 4" grinder with a thin metal cut off wheel and was wondering what the different metals are inside? Was thinking that a magnetron could possibly be used as a spark gap.? I heard somewhere that a magnatron is actually a diode. Is this correct? Just watched a vid of someone blowing air up a Jacobs ladder making a plasma flame thrower basically. Thanks for all the videos, recently found your channel and appreciate you sharing your knowledge.
I have used these before to generate high voltages. They are crazy powerful and can create even higher voltages than the iron core transformers. Unfortunate that it was broken, but on the other hand it was probably for the better. One of the opto couplers is simply an enable input, the other one seems to be some sort of state output but it's not required. Simply apply a small voltage like 3.3V between the enable wire and the common wire and the inverter should turn on. Unfortunately mine broke after a while, they can be damaged way more easily than the transformers as you said.
I got a broken inverter microwave from a 2nd hand store and harvested the IGBT and a bunch of other goodies from it. Infineon makes tough chips. I've put it through hell and it keeps kickin
I’m amazed at how common that non-symmetrical half bridge type of inverter is. I’ve seen it in CFL ballasts and step down halogen power supplies. I think I’ve seen it in an ATX power supply and maybe this (or the symmetric 2-capacitor version) in a small inverter welding machine
From all that I’ve read from other sources, the switching supplies in these ovens operate at about 50KHz. That makes them much more efficient than the 60Hz transformers. The ferrite core in them is built to run in the 20 - 50KHz range. I’m looking for one of these boards to rewind the secondary for low voltage, high current output. With this high frequency, copper coated aluminum wire must be used due to the skin effect of electron flow. Using solid core wire is a waste here.
I bought a second hand inverter microwave for cheap years ago, it worked fine for about 6 months before it popped and emitted the magic smoke. I didn't even bother opening it up to find out what went bang, just threw it out at the next council clean-up. The standard one I bought to replace it lasted about 10 years before it started making a zapping noise. My friend had just renovated his kitchen and had a spare microwave, so I got that for free. Then I found out the zapping noise might be the waveguide cover, so that could be a cheap fix. I did keep that microwave, so I probably should just get the replacement waveguide cover and see if it fixes the problem, then I'll have a spare microwave.
This seems like some kind of active clamping soft switching forward converter, instead of the normal fly back converters. The primary capacitor is placed such that it functions as a series resonant LC tank, and the top transistor is probably the smaller one for clamping the "reset" current (inductive kick back). It's very likely that the main switch is operating with soft switching, and the auxiliary switch could also be soft switching if designed correctly.
Also to mention, in some soft switching converters, only the primary switch is designed to be soft switching since it sees the most amount of current, and larger switches have more switching losses. The AUX switch doesn't need to be as big and consequently has less switching losses, therefore the switching losses from hard switching is acceptable.
For this circuit to have high power factor it probably operates just like the ZVS induction over circuit. High frequency modulated by the 100Hz nains ripple.
Great Video, great explanation! I like vintage power supplies 😀. I have been sleeping for years with my ears next to my mains alarm clock which has/had switching power supply integrated I not like anymore. It produces high mosquito sound I nowadays suffer from tinitus with exactly this high frequency white noise of this mosquito sound in my ears. And I cannot hear very high frequencies from outside anymore. Thanks so much for favourite linear older transformer power supplies! 😀
The working frequency of the transformer seems to be around 50 kHz, because the 3rd harmonic is very strong about 150 kHz and is causing differential mode disturbances.
Microwave ovens' inverter power supplies are much more expensive but also far more efficient compared to the Iron transformers, not to mention it doesn't throw out your back when moving the oven. Of course and some inverters are managed by software meaning the gate of the main chopper transistor is driven by a programmable timer on microcontroller die, making it a bit easier for some pricey and better microwave ovens to finely tune how much watts in microwave output to pump out.
Lots of comments about the unreliability of inverter microwaves, but nothing about how much better they actually work. I have an older Panasonic inverter unit that still works great, and if it died tomorrow I would immediately buy another one. They work *much* better than transformer-based microwaves, especially at low power settings. If you set a transformer microwave to 50% power, it doesn't actually produce half power. Instead, it cycles on and off at 100% power but the user has no control of the duty cycle, so short durations at low power aren't really possible. An inverter microwave will actually produce half power, so your food is much less likely to boil or explode. Sadly, most people don't bother to learn how to use a microwave properly; they just run it at full power all the time and clean up the occasional mess (or don't, and have a disgusting microwave!).
First time, I am seeing a SMPS for microwave. We have so many flyback and other power supplies which reduces the voltage, this SMSP microwave is rare case used to increase voltage.
i repaired such thing like a 10 years ago in grandma's oven and it still works today :D fault was just open 20 ohm resistor in one of gate driving circuits. i heard later it's a common fault in these inverters
Fun fact: this little guys actually exists in some microwave ovens since 2010 or sooner (I've just found it out by some research on UA-cam... Just found the oldest video about them)
This should have come with an extra warning, these are very dangerous. Teens use to die trying to make ark patterns working with wood, applying the HV to a board. Only use I'd recommend is using this stuff for high current, it's possible to spot weld batteries with a transformer like this. Get rid of the HV coils ASAP, replace 'em.
There's a warning at the beginning of the video. There's a warning in the description. There's a spoken warning when I test the MOT. And there are the calculations that also give a lot of a warnings and scare the hell out of people. If it's still not enough, I don't have much hope for humans...
@hardstyle905Point is, there is no room for error, you are just kill. It's riding a bicycle compared to riding a 1000ccm super sport. I never got an electric shock except cattle fences, and I played with tubes, and messed around working in big solar parks.
I'm guessing you mean the price? I've been out of MWO repairs for quite a few years, but I randomly Googled and (being in Australia) an LG inverter for many of their models would cost AUD99.95 (USD65), including Tax and without any trade discounts. LG prices are pretty good, inverters for other brands like Panasonic or Sharp would cost more. But as usual with electronics, volume production lowers costs.
Is this how the more expensive microwaves operate, the ones that don’t need to switch on and off at lower power settings and that don’t have a turning glass plate?
Meh I wouldn’t really call these “expensive” because the flaw in this statement is that the price will naturally drop overtime- but yes they are for now. Inverter microwaves.
"The ones that don’t need to switch on and off at lower power settings" Yeah, that's inverter microwaves. The ones without a turning glass plate are usually inverter but they don't have to be as they use a regular magnetron pumping RF through a waveguide into a chamber with a turning metal disk located underneath the floor of the oven, which is what eliminates the need for a turning glass plate.
Inverter microwaves can modulate, but only to a certain level. Since the filament voltage comes from the same transformer, it would drop to low They usually operate continuously down to around 50% of power. Beyond that, they cycle on and off like a normal microwave does
Very informative video, Thank you. At 10:10 onwards, what (kinda a self made) device you are using with single 7 segment display & two crocodile clips to measure transfotmer windings? What does it measure?
I love the detail that the socket of the multioutlet have soot inside after some serious black magic smoke release . I e that aint normal white magic semiconductor smoke. That is black magic smoke. The baad soot.
Ďakujem ti za toto videjko, už som o spínaných zdrojoch pre napájanie magnetrónu v mikrovlnke niekde počul, ale viac som sa tým nezaoberal, takže som si rád pozrel ako je to vlastne skonštruované.
Create a driver circuitry for the transformer using a MOSFET and 555 timer! I'd really love to see that. You could also make the arc produce music by inputting some music signals to one pin of the 555 timer. I've built one of these driver boards
just a ZVS or even better if you wanna do an NE style, a TL494, much better for audio modulation problem is that the voltage is really, really low compared to a CRT flyback so it will be hard to maintain a stable long arc especially for audio modulation
@@TomboRectify i mean the output voltage, these are made to put out approx 4kV at high current, just like the metal transformers (the metal transformers go through that capacitor and diode as a half wave voltage doubler), a TV flyback from an actual TV puts out anywhere between 20-35kV (dependant on TV size) on the stock driver
Hoping to see that "inverter" powered up, it should just need a PWM signal. I study power electronics, and these are super interesting; they are usually quasi resonant active clamp forward converters, and some are resonant flybacks. I also have the Matlab code for the optimization surface computation for selecting the key component values.
They use a power wave envelope scheme similar to an induction cooker, also it uses a handshake signal from the control board and that also tells it hey set the power to xx.xx%. It also tells the control IC that all is well at 120 or 100hz. The most common fault with these are the rectifiers that do not seem to be truly designed for HF operation.❤
MOT transformers are mostly gone in the 120v mains world. I visit many *Sally Anne* used goods stores for cheap parts and inverter ovens are all I see now for a decade. This one seems to be from Panasonic. DGW, what about making safe a Hi-Pot tester for doggy power adapters?
I remember BACK in the day replacing these in Ovens and having to send the old one back to Panasonic for them to rebuild it and send it to the next peeps.
Yes, the rework program. When the Panasonic Inverters were released in 1988 I had been a technician for 13 years and ran the service department for an electrical retailer.
@hardstyle905 It may be a single-transistor forward converter, some time ago I tried to replicate a Soviet scheme of an inverter welder with this topology, which uses a regenerative snubber in the hot part of the circuit. I don't know if it has anything to do with the microwave inverter.
Hey i interested to buy lg inverter microwave but how about power regulation? Its just on and off or swithing with linear power? (If i select 50% power its 50% watt or just cycling ar 50% on time) thank you.
@@widyahong A mix, depending on how hot the transistors are, it will switch to 50% power for a few seconds and then turn off for a few seconds. The power is set from about 50% to 100%, less than that switches it on and off.
Cherry lime ricky cook aid recipe. Drink at own risk! Half a packet of lime, grape, and dark cherry cool aid 1 cup sugar and two liters distilled water. Super tasty. If you want to turn it into gatoraid just add a teaspoon of your favorite sea salt or rock salt.
Can You tell Us if it is enough to touch it once and you're dead, or will this contract your muscles and won't let you loose(Carbon, powder)??? Thank You in adavnce.
What I have thought of for a good while is why you need the voltage doubler at all in microwave ovens instead of using a transformer outputting 4000-5000 kV directly to the magnetron? Does it have something to do with insulation capabiities of the transformer at this size or something similar?
Yes, greater difficulty and cost for no advantage. The voltage doubler is ideal for the purpose - half the voltage handling requirements for components (transformer, rectifier, capacitor) which would otherwise have to be far greater voltage rated, and draws power on both half-cycles of the mains (desirable) rather than only one for a simple half-wave system.
I ran the single transistor version of this inveter and it wants a 220Hz 5v squarewave PWM 100% positive offset on the input opto. it needs to be at a low duty cycle to start say 20 percent iirc
I can tell you I don't have time to die from my fractal burner. When I had the capacitor in parallel the primary caught fire. And 10.000 volts hurts really bad. So I removed the capacitor and 2.100 volts doesn't hurt as much but it is much harder to let go of.😅
Add lot more diode and HV capacitor to voltage multiplier section then connet it with an x-ray tube. It is will be as dangerous as possible. Never combine HV with HF. It is cut thru any isulation, what are usualy works well at low frequency.
It doesn't matter because the transformer in question has no connection .. electrical or (static@50Hz) capacitive to any earth/grounding and most importantly the other hand or no body part is in physical contact with the other bare wire.
@@analoghardwaretops3976 I think that's a dangerous statement to make because of the voltages involved. The primary is most likely not insulated for 2kv, so if you touch the high voltage lead to real ground the transformer core will go live at high voltage and it could arc over to primary.
@@eDoc2020 50/60 Hz Tx. under test..one can clearly see the pri. & sec.are wound on two separate bobbins. & printed schematic shows an isolated stepup secondary. So question of pri. " isolation " doesn't hold..besides all testing has been on an insulated work table... Even feeding the pri. through an additional 2/3/5kV isolation transformer will be of no more saftey than this demo setup. Usually wires for 2-3kV voltage potential will have insulation that has to withstand at least 7.5-10kV b.d.v. besides to comply with safety standards...engineers/ designers will have considered most of " your " IF's & BUT's doubts before a product evaluation /release. so D.G.W. is very capable and cautious & also knows the consequences..and has taken sufficient precautions for this demonstration.
@@analoghardwaretops3976 Sure the secondary has good insulation but the primary is only intended for 230 volts. I agree what DGW was doing was safe, I was just pointing out that your comment could lead to disastrous results if people used it as general safety advise for their own experiments.
Hi, I bought some time ago a Panasonic Inverter microwave, it worked for just 7 month and now it's not working, I hope ti find answers in your video, I am sure it's the inverter switching supply and I'm waiting to check all the components.
Thank you very much for sucha an interesting video. Just this week I asked a good friend of mine a question: why are not microwave ovens that work at 50 or 60 Hz made with ferrite cores. He is very good in electronics and had to think a bit. He said probably it was because steel cores have a higher permeability and saturation, and that would make the steel transformers cheaper at low frequencies because less copper was needed. He said at high frequencies that would change. I hope you agree with that reasoning, and in the contrary, it would be interesting to hear your opinion. Thanks again.
Yes, at such a low frequency as 50 or 60Hz, you primarily need the permeability to be as high as possible. Ferrite has a much lower permeability. Even with iron, the cores still have to be big and the numbers of turns high. On the other hand with tens of kHz, cores are small and numbers of turns are lower, but the core has to have low losses (hysteresis and eddy current) at such frequency, so iron is unuseable, ferrite works much better.
The specific schematic onscreen? It's completely visible, so take a screen shot? Print if desired. Or copy by hand? The Czech source site is watermarked on the image, but nothing identifies the type of microwave that schematic is for - it is rather characteristic of older model Sharp units.
If the transformer's output impedance is almost the same as the human's worst case resistance, this make the system an impedance matched (closely) system, and ensures *maximum power transfer*. Spooky!
Yes, this is exactly what I also noticed. Perfectly impedance matched to a human :). Or at least matched to the center value. The transformer is 1000 ohms, the human starts at 1500 ohms an gradually reduces to 500 ohms as the skin turns into carbon.
Interestingly a higher current like 1A can be sometimes less dangerous than 100 mA. With 100 mA, only some of your heart muscles stop, making them out of sync. A higher current stops all your muscles and if your heart restarts it is more likely to restart in sync. A defibrillator deliberately stops all heart muscles for this reason.
since you are'nt fixxing this board to test it, I bet you would do an autopsy of the transformer... missed that part. Other than this, nice video as always, I haven't seen one of those inverter microwaves' board before.
I guess as long as there is plenty of cheap recycled steel available (if you use an arc furnace to melt it, it even tells you for free what impurities are present .....) and the machinery to make the mechanical timer and power regulator units is still working, then there is less of a benefit in changing a power supply design that has worked fine for over 50 years.
I wonder how the electronic microwave supply affects the "compatibility" of the microwave with other things operating at the same 2.5GHz like Wifi or so, when few W of the microwave energy will always escape the oven and the communication is limited to barely 100mW. Normally the communication protocols rely on the fact that traditional microwave oven circuit powers the magnetron only for one halfwave, so the communication can work during the other halfwave (8..10ms). But when the magnetron gets powered for both halfwaves, the quiet time becomes very short, too short to be sufficient for anything usable.
The inverter microwave I'm familiar with blanks all wifi in the room, there's a home theater remote speaker in the kitchen that uses 2.4ghz and you can hear the audio break up as the cathode comes up to temperature. Worth it for the true variable power and higher max power.
Those eMOT modules make truly awsome HV power supplies if you swap the original transformer for a high frequency x ray head transformer. You do have to make several modifications to it because these boards handshake with the control board.❤
Nice video, On the Iron core MOT circuit how does the voltage get doubled by using just 1 capacitor and 1 diode wired as a standard half wave bridge rectifier?
It's NOT a standard half wave bridge rectifier. One halfcycle charges the capacitor and then the voltage of the capacitor is added to the other halfcycle. It produces a pulsed voltage, not smooth DC.
I definitely wash my hands after soldering, especially because of the leaded solder. When I finish building something that's to be used in a clean area, I clean the outside of its box, so I don't have to wash my hands after touching it.
By the way do you wash your hands after you use your smartphone and laptop. I've seen you use your laptop while soldering to show us the spectrum of lamps. SO do you wash your hands BEFORE using the laptop? AND do you use your smarthphone WHILE soldering,OR do you wash your hands FIRST,THEN USE THE PHONE?
The proper way to play with MOT's and other HV transformers is to use proper 15-30kV or higher rated wire and using a "chicken stick" preferably a official lineman one, but a piece of glass fibre rod if you can find/afford around 1.5-2 meters of around an inch thick, or in worse case a piece of like plastic cable conduit. But when it comes to tesla coils i prefer the CW solid state ones anyways, as the spark gap coils are just way too noisy for my taste.
Yes, MOTs can surely be handled way more safely ;). SGTS is quite loud and smelly, so I also prefer SSTC. You can play with it longer before it becomes unbareable ;).
The only real benefit to inverter based power supplies is powerfactor. That and it's less likely to kill idiots because they typically break before you can do anything silly with them. I like fancy inverter stuff but only when schematics and stuff is available. Proprietary non serviceable designs are basically E waste
I think most intetesting for people are repairing battery powered tools like drill battery and their charger. I have made many repairs but not upload to my channel. Lets start together to share knoledge.
Can somebody provide some insights as to why the capacitors in the doubler circuit are different values? This seems to be the case in every microwave inverter I've seen.
They are the same value in the older Panasonic Series 2 inverter I have in front of me, but later series certainly use two different values, usually when they are a single ended parallel resonant converter, which is not symmetrical in operation. The capacitors are resonance capacitors. Not simply energy storage for the power output, but a time constant in resonance with the transformer inductance, as is also the case with the much larger single capacitor in the mains transformer designs, them at 50 or 60 Hz, these at tens of KHz. I hadn't seen specific discussion of the capacitor values but I did find a technical document that covers it. Linking away from UA-cam is problematic due to rules, but if you search for "Parametric Design Guidelines for MW Oven Inverter" you should find it. If necessary add Bocchiola.
From the flux residue on the back, I can assure you the transistors have been replaced before. Good old school transformers are the best. Semiconductors burn with a smelly fart in the presence of high voltage.
This is an excellent comments section and a well informed video too.
I've just repaired my Panasonic microwave and worked through the circuit on the inverter to checl the components.
Before the the inverter there is LC and MOV filtering with single glass fuse. Energy is switched with a spst relay on line. Safety interlocking shorts the line and neutral if the relay is closed, but the door opened (user exposed to rf).
Idle current for the inverter (230volts ac) is
Finally on a unique topic....I hope inverter microwave oven won't replace traditional microwave ovens
Not me, they use less power and the Toshiba ones made by Midea last LONG time, and cheap to fix yourself.
Well done for resisting the temptation to power up the switching power supply, you had me worried for a moment. The arcing out put from the iron transformer and numerical output from the catculator are a very good deterrent against dismantling my microwave.
Quite a while ago, MikesElectricStuff took a look inside an inverter microwave that got completely trashed by the bulb blowing. It blew a PCB trace when the bulb blew, and the arc flash from that trashed the logic circuitry effectively rendering the whole thing scrap. Sometimes simpler is better...
I am surprised these inverter microwaves haven't taken over yet, switching PSUs have taken over nearly everywhere else
I guess that inverter microwaves didn't take over because the iron core transformer is more reliable.
@@Alexelectricalengineering or maybe cheaper than a switching supply? I mean, nowadays the MOTs have the absolute minimum amount of metal in order to work. Nothing like what they used to make...
Well, the inverter side needs actual copper wire in the unit, while the iron transformer just uses CCA wire. It is a lot cheaper to stamp out iron laminates, and wind the CCA wire on formers, on machines long since paid for. Low cost materials, low cost labour, and as you ship by sea volumetric mass is the rate used, as a microwave oven is almost all air inside, even with a 2kg lump of steel in it. The inverter ones are only used where you are paying much more for more precise control, as they allow cycle by cycle PWM switching, so instead of the iron core having a PWM over a 30 second repetition period, you now have it based on the input mains frequency from the control panel, so the apparent power delivered seems to be much finer, as it is being adjusted either 100 or 120 times a second, per cycle power limiting.
And yes, even on a regular microwave that lamp blowing can take out the 10A ceramic fuse, I have changed many fuses along with the lamp, and modern ones now also use an 8A fuse in 230VAC countries, as it is cheaper, and include a soft start circuit to limit the inrush current into the transformer as it turns on into a cold filament of the magnetron, or with the duty cycle switch turning it off for a few seconds every half minute.
@@liam3284 The microwave fuse does that, though I have seen even 15W incandescent lamps trip a 63A main breaker when blowing. Lamp in a ceiling, with old 4mm wiring to it, so a really low impedance supply. Did not blow the replaceable wire fuse, though that could have been because some previous tenant had replaced the 5A fuse wire with 1.5mm copper wire doubled up, years before, so it would never blow, except for a dead short for 10 seconds.
now you know why the new ones do not last half as long, we replace 1 part with 100 parts, of which many have a lifetime of less then 1000 hours. we call this "progress".
The switching power supply is much lighter than the iron core transformer. Much cheaper to ship. Money saved ... that is all.
@@chuckvoss9344 Not in a microwave, where you pay volumetric mass, as the cavity is all air.
Microwaves with these power supplies are inverter microwaves, which aren’t subject to the long-period on/off duty cycles to deliver partial power. In other words traditional microwaves with normal transformers run full-power for 5 seconds and then zero-power for 5 seconds, to provide 50% power. But microwaves with this kind of power supply do not have these long-period duty cycles to achieve partial power. So it actually is “progress” if you care about heating food more smoothly.
My guess is you could have a decent switching supply that would last the life of the microwave, as long as you don't skimp on decent parts and have sensible board design.
@@HobkinBoi I will say that in general the iron core transformer is generally really reliable. They do fail with shorted turns with the CCA wound ones, and a replacement is as expensive as a new microwave, so the good ones from scrapped units are pressed into service instead.
I have scrapped more microwave ovens for the cavity rusting through where the turntable runs, and, for the recent few microwaves, the failure was the actual RF filter assembly on the magnetron arcing over internally, which is a really odd thing to have, as those are pretty much just a thick ceramic tube, with silver plate on the inside and outside, potted in hard resin. I guess they are using cheaper materials there, leading to the failure. Despite the high power it generates, the only failures in magnetrons is from the output probe arcing over from dirt in the waveguide cavity, from the mica or RF transparent plastic cover either breaking, or being dirty and burning up.
Only ever had one fail due to age, but seeing as it was 30 years old, and went low output, it had definitely done well. Replaced with another used one, that was younger by around a quarter century, and in good condition, with the right fin and mount orientation. Also had one fail with a broken filament, but to be fair that oven had taken a trip off the table to the floor before that.
From reading up on prior literature and from what I can tell, the large inductor on the DC bus is used both as a current source for the resonant tank circuit and as interference suppression, the top IGBT is used as an active snubber with the 3.9uF capacitor, and the bottom IGBT drives the resonant tank circuit (formed by the 180nF capacitor and the transformer primary. similar to a single ended induction heater). I can dig up some of the patents and schematics that Panasonic devised for the inverter technology if anyone is interested.
For his schematic it was clear that it isn't a half-bridge, as he claimed. You confirmed my suspicions that it is resonant and that the upper IGBT is an active snubber.
It is nearly impossible to achieve low leakage inductance with a transformer wound in that way, and that winding design is pretty much essential to for the voltages involved without running the cost way up. My guess is that the leakage inductance is used to advantage in the resonant circuit.
I salvaged a comparable board from a dead MO. I figured that these would help make the devices die earlier since any switching PSU has a much more limited lifetime than a good old passive transformer. However I figured it did have some benefits. The board had a PWM entry to smoothly reduce the power output. And that's nice because you don't have this with the regular transformer. Instead when you want 300W, it does 900W for 10 seconds, and 20 seconds pauses, which is a disaster for small pieces of food that you don't want to burn. It also alternates heating and cooling of the magnetron which certainly shortens its lifetime. So there are actually also some good points in having an electronic PSU instead of a transformer.
HAM operators of the world whil be delighted. LEDs, all sorts SMPS and now a 1kW noise souce in every house...
I'm looking at it musing if I can use it as HV supply to build a ham radio tube linear power amplifier. 😂
I wonder if they connect to the 2 sides of the heater to disable the doubler & prevent excessive voltage/arcing if the filament goes open or is disconnected
if the heater goes open, there's still the low voltage winding.
I've found basically the same power inverter like 7-8 years ago, when I was a kid. Don't remember much but transformer, heatsink, big resistor and HV diode look very familiar, I still have that 15W resistor and diode! Back then I didn't know much about this stuff and I wondered why 12V bulb barely lights up powered via a diode (large voltage drop), or why transistors "don't work" (they were dead-shorted, just like yours). Thanks for bringing back some memories
Yep, I tore apart a Panasonic microwave as a kid looking to tempt fate with some microwave oven transformer experiments and was disappointed when I was met with this style of board. Probably for the better that I wasn't able to mess with high voltage lol
This is a standard module, introduced in the 1990s and in use in almost every brand of microwave ovens.
Saw my first one in a restaurant (not rated nsf) health dept said dumpster it... lol I never saw the inverter work, stuck some guts from an old goldstar in it .... worked great! That was in 2009...
😊
To power it up, you connect the brown wire to ground, orange wire through a 10k resistor to ground, and feed a 220hz PWM (TTL, so 3.3v to 5v) square wave signal into the yellow wire. The duty cycle has to be below 43% when first powered on.
@andrew_koala2974
After 13 years teaching and 30 years in the military, I would be on the assumption that your life would have come to something better than flaming person on simple comment on a UA-cam video. I know life might have become harder for you after your daughter left you to go work in NYC, usually people can fall into a spiral of depression and sadness after they children have left them but for you I think it has led you to fall in a spiral of mental insanity. Previously one of your comments on one of your videos flames a simple comment voicing their opinion about the music choice, but no you had to attack that person for a simple missed correctly spelt word 'your' instead of using 'you are'. Many highly acclaimed people unlike yourself do not solely focus on ones spelling but the context and reasoning behind their comment. Around the UA-cam community uploading videos in 720p is not acceptable for viewing, 1080p is the standard in the community but yet after your 13 years of teaching English and History and 30 years in the military it would be assumed that you would understand the UA-cam Algorithm and see that uploading in 720p is not beneficial and almost every current phone can stream and most can even video in 1080p or even a higher resolution, so after your UA-cam videos in the past year don't even bring in an average of 30 views but your mentally insane brain can not comprehend that less than 30 views in not good performance. Any normal person would either give up or change the way they produce and upload their content but you brain does not understand that you should change your videos or give up. To Summarise you have passed the line between insane and normal. Flaming people's UA-cam comments is not acceptable or healthy for anyone. Go put close UA-cam and hide in Sydney, and leave all these peoples UA-cam comments alone.
based@andrew_koala2974
@andrew_koala2974 👍🏻👏🏻💪🏻
I have your online calculator pinned on my phone's home screen and I just named it "🐈culator".
I love it and use it a lot. 😄
great idea, I'll try it too
There is other aspect of this power supply: Normally on a "700W" microwave the magnetron itself is a 1.4kW device, it is just because operating at half of the time makes the 700W of it. This supply powers the magnetron by all the time (I mean both mains halfwaves, neglecting the 100Hz), so it may really get the full 1.4kW out heating microwaves from it. Just reducing the current won't work, as it would cause severe degradation of the magnetron efficiency: The 2.4GHz AC amplitude inside needs to match the magnetron voltage to get the ideal efficiency (no excessive drop across the electron stream), wgile the total voltage can not be lower, as the electron speed has to match the resonant frequency of the cavity.
Ive salvaged many of these. They have some neat parts. I remove the primary and apply standard 5T + 5T and normal irfp250 zvs. Not ideal output for pretty arcs as ratio way too low, even with lower pri. Just high current ac that burns even aluminium immediately. I remove sec and rewrap with .3mm from the fan motor and drip on epoxy in process, can fit on 1500 turns easy, and makes a pretty resilient hv coil. Also make a big ferrite out of two matching transformers, and same for hv coil. Makes a pretty kick arse high current and hardwearing transformer.
The mw's with the EE ferrite and secondary inside the primary have the best bobbins for the secondary, but not suitable ferrites. The mw's with the UU core are best for ferrites that can be mixed and matched. Seems about half are big, and about half slightly smaller, but only 2 sizes, no matter what mw they come from. Thats what i use them for anyway.
The doubler circuit is connected to the cathode in this special way to disable voltage doubling when the heater wire is broken. A magentron without heater but with high voltage could emit some other radiation.
Well, this also came to my mind, but the two points are still connected via the low voltage secondary.
That's right, maybe they chose this way because it was easier to connect, since the doubler capacitors are mounted on the side of the bobbin?
It won't amit any other radiation. With a cold cathode, you have no current. Magnetrons do produce X-rays in normal operation, but 4 keV is too low energy to pass through the copper anode. Even a thin glass vacuum tube will block X-rays under 10 keV.
@@mernokimuvek You're right, I didn't think about the low keV, but magentrons can produce X-rays when the filament burns out but is still hot enough to emit some electrons. You will get a hotspot which will give you enough electrons for a accelerated path inside the tube. Once you disconnect it, it cools down and then will never generate anything again. Correct me if I'm wrong... I thought the beryllium stem of the antenna was quite 'translucent' for X-rays?
@@SunnyJulienDivine I tried disconnecting the heater and it stoppe emitting microwaves in a few seconds.(With the high voltage still connected). The beryllium oxide or aluminium oxide insulator is still a few mm thick. X-rays tubes with thin beryllium windows rarely emit under 7 keV.
Thanks dgw!! A great reminder to not bother playing around with the electronic transformer. I have 5 of them and another channel shows how to get it working but I have decided not too and as you say they are fragile to experiment with . Cheers
NICE man. Been waiting for you to get your hands on one of these.
You can make a ZVS that runs on mains current to power that transformer, it should work fine and with plenty of power.
Uuum, ZVS ?
Zero Volt Switching ?
I have a bad memory...
yep.
@@snakezdewiggle6084
@@snakezdewiggle6084mazzilli ZVS driver
The 3 small wires (brown/orange/yellow) are PWM input for adjusting the power level and a feedback signal for the oven control (half of the PWM signal). both signals are using opto couplers. There exists also a smaller variant of this module with one IGBT and the DC capacitor has 3 µF and not 5 µF.
This principle seems to have a small disadvantage: Reducing the output power will also reduce the voltage for the filament of the magnetron.
I gues the heater voltage doesn't vary that much, because the main load is the anode-cathode current, that doesn't affect the voltage drop much. The magnetron simply tends to drop about 4kV no matter the current. This clamps the transformer voltage per turn to a sort of constant value. The anode winding is probably between the primary and the heater winding for this reason. The anode winding is like a bi-directional zener on the heater winding :).
I just tore apart my first microwave magnetron, I used my 4" grinder with a thin metal cut off wheel and was wondering what the different metals are inside? Was thinking that a magnetron could possibly be used as a spark gap.? I heard somewhere that a magnatron is actually a diode. Is this correct? Just watched a vid of someone blowing air up a Jacobs ladder making a plasma flame thrower basically. Thanks for all the videos, recently found your channel and appreciate you sharing your knowledge.
I have used these before to generate high voltages. They are crazy powerful and can create even higher voltages than the iron core transformers. Unfortunate that it was broken, but on the other hand it was probably for the better. One of the opto couplers is simply an enable input, the other one seems to be some sort of state output but it's not required. Simply apply a small voltage like 3.3V between the enable wire and the common wire and the inverter should turn on. Unfortunately mine broke after a while, they can be damaged way more easily than the transformers as you said.
I got a broken inverter microwave from a 2nd hand store and harvested the IGBT and a bunch of other goodies from it. Infineon makes tough chips. I've put it through hell and it keeps kickin
I’m amazed at how common that non-symmetrical half bridge type of inverter is. I’ve seen it in CFL ballasts and step down halogen power supplies. I think I’ve seen it in an ATX power supply and maybe this (or the symmetric 2-capacitor version) in a small inverter welding machine
From all that I’ve read from other sources, the switching supplies in these ovens operate at about 50KHz. That makes them much more efficient than the 60Hz transformers. The ferrite core in them is built to run in the 20 - 50KHz range.
I’m looking for one of these boards to rewind the secondary for low voltage, high current output.
With this high frequency, copper coated aluminum wire must be used due to the skin effect of electron flow. Using solid core wire is a waste here.
I bought a second hand inverter microwave for cheap years ago, it worked fine for about 6 months before it popped and emitted the magic smoke. I didn't even bother opening it up to find out what went bang, just threw it out at the next council clean-up. The standard one I bought to replace it lasted about 10 years before it started making a zapping noise. My friend had just renovated his kitchen and had a spare microwave, so I got that for free. Then I found out the zapping noise might be the waveguide cover, so that could be a cheap fix. I did keep that microwave, so I probably should just get the replacement waveguide cover and see if it fixes the problem, then I'll have a spare microwave.
That ferrite core is larger than a CRT flyback transformer core so is good for a DIY HV transformer
This seems like some kind of active clamping soft switching forward converter, instead of the normal fly back converters. The primary capacitor is placed such that it functions as a series resonant LC tank, and the top transistor is probably the smaller one for clamping the "reset" current (inductive kick back). It's very likely that the main switch is operating with soft switching, and the auxiliary switch could also be soft switching if designed correctly.
Also to mention, in some soft switching converters, only the primary switch is designed to be soft switching since it sees the most amount of current, and larger switches have more switching losses. The AUX switch doesn't need to be as big and consequently has less switching losses, therefore the switching losses from hard switching is acceptable.
For this circuit to have high power factor it probably operates just like the ZVS induction over circuit. High frequency modulated by the 100Hz nains ripple.
Gotta love those duck shin overs.
It's mains ripple not nains ripple you silly donut
Thanks for sharing your reverse engineering of the switching microwave oven control circuit
Great Video, great explanation! I like vintage power supplies 😀. I have been sleeping for years with my ears next to my mains alarm clock which has/had switching power supply integrated I not like anymore. It produces high mosquito sound I nowadays suffer from tinitus with exactly this high frequency white noise of this mosquito sound in my ears. And I cannot hear very high frequencies from outside anymore.
Thanks so much for favourite linear older transformer power supplies! 😀
The working frequency of the transformer seems to be around 50 kHz, because the 3rd harmonic is very strong about 150 kHz and is causing differential mode disturbances.
Microwave ovens' inverter power supplies are much more expensive but also far more efficient compared to the Iron transformers, not to mention it doesn't throw out your back when moving the oven.
Of course and some inverters are managed by software meaning the gate of the main chopper transistor is driven by a programmable timer on microcontroller die, making it a bit easier for some pricey and better microwave ovens to finely tune how much watts in microwave output to pump out.
How much amps does this transformer use
I read up about it a while ago and If i can recall to bypass the safety and get it outputting HV you need to input a 33khz square wave at 20%
Lots of comments about the unreliability of inverter microwaves, but nothing about how much better they actually work. I have an older Panasonic inverter unit that still works great, and if it died tomorrow I would immediately buy another one. They work *much* better than transformer-based microwaves, especially at low power settings. If you set a transformer microwave to 50% power, it doesn't actually produce half power. Instead, it cycles on and off at 100% power but the user has no control of the duty cycle, so short durations at low power aren't really possible. An inverter microwave will actually produce half power, so your food is much less likely to boil or explode. Sadly, most people don't bother to learn how to use a microwave properly; they just run it at full power all the time and clean up the occasional mess (or don't, and have a disgusting microwave!).
Most Panasonic microwaves are now made by Midea. You have to look well to get a true Panasonic
Some people just want to be the victim constantly.
First time, I am seeing a SMPS for microwave. We have so many flyback and other power supplies which reduces the voltage, this SMSP microwave is rare case used to increase voltage.
How difficult would it be to rework this SPS to 12V - or better 48V?
A convenient HV power supply. I use one modified to power a VTTC.
Ooo I am interested, can you maybe show me the schematic?
i repaired such thing like a 10 years ago in grandma's oven and it still works today :D fault was just open 20 ohm resistor in one of gate driving circuits. i heard later it's a common fault in these inverters
Panasonic? It was a known fault for them.
@@PlatypusPerspective yep, exactly!
Fun fact: this little guys actually exists in some microwave ovens since 2010 or sooner (I've just found it out by some research on UA-cam... Just found the oldest video about them)
At work we have a Siemens microwave built by Panasonic. It’s an inverter as well, made in 2000
@@MieleW2573 oh nice!
Panasonic released their first volume production domestic inverter MWOs in 1988. I'd been a technician for 13 years and had to learn how to fix them.
This should have come with an extra warning, these are very dangerous. Teens use to die trying to make ark patterns working with wood, applying the HV to a board. Only use I'd recommend is using this stuff for high current, it's possible to spot weld batteries with a transformer like this. Get rid of the HV coils ASAP, replace 'em.
There's a warning at the beginning of the video. There's a warning in the description. There's a spoken warning when I test the MOT. And there are the calculations that also give a lot of a warnings and scare the hell out of people. If it's still not enough, I don't have much hope for humans...
@@DiodeGoneWild I know, looked to me like the text before all the vids here. No offense intended, these things just give me chills.
@hardstyle905Point is, there is no room for error, you are just kill. It's riding a bicycle compared to riding a 1000ccm super sport. I never got an electric shock except cattle fences, and I played with tubes, and messed around working in big solar parks.
Nice circuit analysis as always! 😁
Damn, high-power high-voltage high-frequency diodes? And that's just getting started, I can't dare to imagine the prize of this!
I'm guessing you mean the price? I've been out of MWO repairs for quite a few years, but I randomly Googled and (being in Australia) an LG inverter for many of their models would cost AUD99.95 (USD65), including Tax and without any trade discounts. LG prices are pretty good, inverters for other brands like Panasonic or Sharp would cost more. But as usual with electronics, volume production lowers costs.
Is this how the more expensive microwaves operate, the ones that don’t need to switch on and off at lower power settings and that don’t have a turning glass plate?
Meh I wouldn’t really call these “expensive” because the flaw in this statement is that the price will naturally drop overtime- but yes they are for now. Inverter microwaves.
"The ones that don’t need to switch on and off at lower power settings" Yeah, that's inverter microwaves. The ones without a turning glass plate are usually inverter but they don't have to be as they use a regular magnetron pumping RF through a waveguide into a chamber with a turning metal disk located underneath the floor of the oven, which is what eliminates the need for a turning glass plate.
@@albatross_v2 Thank you very much!
@@Conservator. No worries. I've seen you comment on this channel for quite some time.
Inverter microwaves can modulate, but only to a certain level. Since the filament voltage comes from the same transformer, it would drop to low
They usually operate continuously down to around 50% of power. Beyond that, they cycle on and off like a normal microwave does
Very informative video, Thank you.
At 10:10 onwards, what (kinda a self made) device you are using with single 7 segment display & two crocodile clips to measure transfotmer windings? What does it measure?
It's a ring tester. It tests the Q factor of the windings. If it's very low, it tends to indicate short turns in the winding.
@@DiodeGoneWild Thank you
I love the detail that the socket of the multioutlet have soot inside after some serious black magic smoke release . I e that aint normal white magic semiconductor smoke. That is black magic smoke. The baad soot.
Ďakujem ti za toto videjko, už som o spínaných zdrojoch pre napájanie magnetrónu v mikrovlnke niekde počul, ale viac som sa tým nezaoberal, takže som si rád pozrel ako je to vlastne skonštruované.
Create a driver circuitry for the transformer using a MOSFET and 555 timer! I'd really love to see that.
You could also make the arc produce music by inputting some music signals to one pin of the 555 timer. I've built one of these driver boards
Skip the transistor and use a vacuum bulb for more fun.
just a ZVS or even better if you wanna do an NE style, a TL494, much better for audio modulation
problem is that the voltage is really, really low compared to a CRT flyback so it will be hard to maintain a stable long arc especially for audio modulation
@@BH4x0r You mean the output voltage OR the amount of current you need to drive that transformer, which makes the voltage low?
@@TomboRectify i mean the output voltage, these are made to put out approx 4kV at high current, just like the metal transformers (the metal transformers go through that capacitor and diode as a half wave voltage doubler), a TV flyback from an actual TV puts out anywhere between 20-35kV (dependant on TV size) on the stock driver
Why don't YOU try that? I swear I would love to see that :D
Hoping to see that "inverter" powered up, it should just need a PWM signal.
I study power electronics, and these are super interesting; they are usually quasi resonant active clamp forward converters, and some are resonant flybacks. I also have the Matlab code for the optimization surface computation for selecting the key component values.
They use a power wave envelope scheme similar to an induction cooker, also it uses a handshake signal from the control board and that also tells it hey set the power to xx.xx%. It also tells the control IC that all is well at 120 or 100hz. The most common fault with these are the rectifiers that do not seem to be truly designed for HF operation.❤
@christopherleubner6633
Yeah, called an Error Amp, and Feedback.
Handshake is just another term for Successive Approximation.
Isn't this more like an LLC/LCC converter instead of forward?
MOT transformers are mostly gone in the 120v mains world. I visit many *Sally Anne* used goods stores for cheap parts and inverter ovens are all I see now for a decade. This one seems to be from Panasonic. DGW, what about making safe a Hi-Pot tester for doggy power adapters?
I remember BACK in the day replacing these in Ovens and having to send the old one back to Panasonic for them to rebuild it and send it to the next peeps.
Yes, the rework program. When the Panasonic Inverters were released in 1988 I had been a technician for 13 years and ran the service department for an electrical retailer.
My LG microwave oven It also has it and it makes a buzzing noise close to 25khz and only have one IGBT transistor.
Maybe a flyback topology? Not sure but I have seen microwave inverters with single IGBTs and dual (but different) IGBTs.
@hardstyle905 It may be a single-transistor forward converter, some time ago I tried to replicate a Soviet scheme of an inverter welder with this topology, which uses a regenerative snubber in the hot part of the circuit. I don't know if it has anything to do with the microwave inverter.
Hey i interested to buy lg inverter microwave but how about power regulation? Its just on and off or swithing with linear power? (If i select 50% power its 50% watt or just cycling ar 50% on time) thank you.
@@widyahong A mix, depending on how hot the transistors are, it will switch to 50% power for a few seconds and then turn off for a few seconds. The power is set from about 50% to 100%, less than that switches it on and off.
@@neonsoft21 okay i understand, thankyou for your information 👍👍👍, i will buy this product..
same ferritte core used in output horizontal transformer in tv sets
Cherry lime ricky cook aid recipe. Drink at own risk! Half a packet of lime, grape, and dark cherry cool aid 1 cup sugar and two liters distilled water. Super tasty. If you want to turn it into gatoraid just add a teaspoon of your favorite sea salt or rock salt.
Can You tell Us if it is enough to touch it once and you're dead, or will this contract your muscles and won't let you loose(Carbon, powder)??? Thank You in adavnce.
What I have thought of for a good while is why you need the voltage doubler at all in microwave ovens instead of using a transformer outputting 4000-5000 kV directly to the magnetron? Does it have something to do with insulation capabiities of the transformer at this size or something similar?
Yes, greater difficulty and cost for no advantage. The voltage doubler is ideal for the purpose - half the voltage handling requirements for components (transformer, rectifier, capacitor) which would otherwise have to be far greater voltage rated, and draws power on both half-cycles of the mains (desirable) rather than only one for a simple half-wave system.
Thank you Sir for this video. Can the inverter board be replaced by using the normal transformer with capacitor and the high voltage diode?
Once again, well done- super video! But touching that thin black wire to another, then explaining, scared me a lot! Where is Your cat at?
Good timing as I just got one of these to play around with myself
I ran the single transistor version of this inveter and it wants a 220Hz 5v squarewave PWM 100% positive offset on the input opto. it needs to be at a low duty cycle to start say 20 percent iirc
I can tell you I don't have time to die from my fractal burner. When I had the capacitor in parallel the primary caught fire. And 10.000 volts hurts really bad. So I removed the capacitor and 2.100 volts doesn't hurt as much but it is much harder to let go of.😅
my I know yes ... thank you DiodeGoneWild best friends
türk varmış ya bu adami izleyen, bende tekim saniyorum
in my home 240 is the lowest i measure so peak 350+ for 250rms
Add lot more diode and HV capacitor to voltage multiplier section then connet it with an x-ray tube.
It is will be as dangerous as possible.
Never combine HV with HF. It is cut thru any isulation, what are usualy works well at low frequency.
I was a bit shocked that Dany just picked up that hv wire bare handed with that transformer just plonked on the desk.
He was actually holding a ground wire.
It doesn't matter because the transformer in question has no connection ..
electrical or (static@50Hz) capacitive to any earth/grounding and most importantly the other hand or no body part is in physical contact with the other bare wire.
@@analoghardwaretops3976 I think that's a dangerous statement to make because of the voltages involved. The primary is most likely not insulated for 2kv, so if you touch the high voltage lead to real ground the transformer core will go live at high voltage and it could arc over to primary.
@@eDoc2020 50/60 Hz Tx. under test..one can clearly see the pri. & sec.are wound on two separate bobbins. & printed schematic shows an isolated stepup secondary. So question of
pri. " isolation " doesn't hold..besides all testing has been on an insulated work table...
Even feeding the pri. through an additional 2/3/5kV isolation transformer will be of no more saftey than this demo setup.
Usually wires for 2-3kV
voltage potential will have insulation that has to withstand at least
7.5-10kV b.d.v.
besides to comply with safety standards...engineers/ designers will have considered most of
" your " IF's & BUT's doubts before a product evaluation /release.
so D.G.W. is very capable and cautious & also knows the consequences..and has taken sufficient precautions for this demonstration.
@@analoghardwaretops3976 Sure the secondary has good insulation but the primary is only intended for 230 volts. I agree what DGW was doing was safe, I was just pointing out that your comment could lead to disastrous results if people used it as general safety advise for their own experiments.
Hi, I bought some time ago a Panasonic Inverter microwave, it worked for just 7 month and now it's not working, I hope ti find answers in your video, I am sure it's the inverter switching supply and I'm waiting to check all the components.
I can't believe changing a simple transformer to a high voltage SMPS will save any money for the manufacturer.
This circuit needs the surge protection of the IGBT transitoirs bc low capacity on primary that can not absorb voltage spikes
Very nice video. Educational, congratulations, have a nice day.
Your online catculator is very nice😂
Thank you very much for sucha an interesting video. Just this week I asked a good friend of mine a question: why are not microwave ovens that work at 50 or 60 Hz made with ferrite cores. He is very good in electronics and had to think a bit. He said probably it was because steel cores have a higher permeability and saturation, and that would make the steel transformers cheaper at low frequencies because less copper was needed. He said at high frequencies that would change. I hope you agree with that reasoning, and in the contrary, it would be interesting to hear your opinion. Thanks again.
Yes, at such a low frequency as 50 or 60Hz, you primarily need the permeability to be as high as possible. Ferrite has a much lower permeability. Even with iron, the cores still have to be big and the numbers of turns high. On the other hand with tens of kHz, cores are small and numbers of turns are lower, but the core has to have low losses (hysteresis and eddy current) at such frequency, so iron is unuseable, ferrite works much better.
Pls , can we know the difference between normal and inverter magnetron , and can we use one instead of the other .
where could I find the schematic at 0:36 ?
The specific schematic onscreen? It's completely visible, so take a screen shot? Print if desired. Or copy by hand? The Czech source site is watermarked on the image, but nothing identifies the type of microwave that schematic is for - it is rather characteristic of older model Sharp units.
danyk.cz/reverz04.html
If the transformer's output impedance is almost the same as the human's worst case resistance, this make the system an impedance matched (closely) system, and ensures *maximum power transfer*. Spooky!
Yes, this is exactly what I also noticed. Perfectly impedance matched to a human :). Or at least matched to the center value. The transformer is 1000 ohms, the human starts at 1500 ohms an gradually reduces to 500 ohms as the skin turns into carbon.
Interestingly a higher current like 1A can be sometimes less dangerous than 100 mA. With 100 mA, only some of your heart muscles stop, making them out of sync. A higher current stops all your muscles and if your heart restarts it is more likely to restart in sync. A defibrillator deliberately stops all heart muscles for this reason.
since you are'nt fixxing this board to test it, I bet you would do an autopsy of the transformer... missed that part. Other than this, nice video as always, I haven't seen one of those inverter microwaves' board before.
I guess as long as there is plenty of cheap recycled steel available (if you use an arc furnace to melt it, it even tells you for free what impurities are present .....) and the machinery to make the mechanical timer and power regulator units is still working, then there is less of a benefit in changing a power supply design that has worked fine for over 50 years.
I wonder how the electronic microwave supply affects the "compatibility" of the microwave with other things operating at the same 2.5GHz like Wifi or so, when few W of the microwave energy will always escape the oven and the communication is limited to barely 100mW. Normally the communication protocols rely on the fact that traditional microwave oven circuit powers the magnetron only for one halfwave, so the communication can work during the other halfwave (8..10ms). But when the magnetron gets powered for both halfwaves, the quiet time becomes very short, too short to be sufficient for anything usable.
The inverter microwave I'm familiar with blanks all wifi in the room, there's a home theater remote speaker in the kitchen that uses 2.4ghz and you can hear the audio break up as the cathode comes up to temperature. Worth it for the true variable power and higher max power.
Are you sure that the 3.9uF capacitor is connected in series with the transformer? It doesn't look right....
It is, and it has to be. It removes the DC which otherwise would saturate the transformer.
Those eMOT modules make truly awsome HV power supplies if you swap the original transformer for a high frequency x ray head transformer. You do have to make several modifications to it because these boards handshake with the control board.❤
afaik all you need is a pwm signal at the input
The overengineered switching transformer vs the simple and reliable MOT
chad mot@hardstyle905
Super! Thank you very much!
Youre a brave guy to trust less than 1mm worth of old insulation on that wire with 2000v. I wouldn't fancy putting my fingers that close!😂😎👍
He was holding a ground wire, not the HV side.
Nice video, On the Iron core MOT circuit how does the voltage get doubled by using just 1 capacitor and 1 diode wired as a standard half wave bridge rectifier?
It's NOT a standard half wave bridge rectifier. One halfcycle charges the capacitor and then the voltage of the capacitor is added to the other halfcycle. It produces a pulsed voltage, not smooth DC.
Do you wash your hands afer soldering,and do yoy wash your hands after using the stuff you made like the thermometers?
I definitely wash my hands after soldering, especially because of the leaded solder. When I finish building something that's to be used in a clean area, I clean the outside of its box, so I don't have to wash my hands after touching it.
@@DiodeGoneWild Thanks a lot,now i can safely use the curcuits and stuff i made
By the way do you wash your hands after you use your smartphone and laptop. I've seen you use your laptop while soldering to show us the spectrum of lamps. SO do you wash your hands BEFORE using the laptop? AND do you use your smarthphone WHILE soldering,OR do you wash your hands FIRST,THEN USE THE PHONE?
Sorry for my crappy English,i'm Chinese.
@@不知所错- why are you so paranoid about solder? There are far more dangerous things like air, water, sunlight, and car accidents.
The last inverter microwave I had apart had a flyback transformer like a TV in it
Please make a video on diy inductance meter
That's a Panasonic inverter, it is used by many other brands (probably because it's not easy to engineer these).
4:12 That transformer is same as found in a CRT monitor/TV.
Interesting looking video.. lets watch.😊
That's was very cool.
Thanks D. 👍🇮🇪🙏
you should get the Belkin 4 Port PD Adapter and open it up.
The proper way to play with MOT's and other HV transformers is to use proper 15-30kV or higher rated wire and using a "chicken stick" preferably a official lineman one, but a piece of glass fibre rod if you can find/afford around 1.5-2 meters of around an inch thick, or in worse case a piece of like plastic cable conduit.
But when it comes to tesla coils i prefer the CW solid state ones anyways, as the spark gap coils are just way too noisy for my taste.
Yes, MOTs can surely be handled way more safely ;). SGTS is quite loud and smelly, so I also prefer SSTC. You can play with it longer before it becomes unbareable ;).
Don't forhet to ballast the MOT. You can use 3-4 40-65 W fluorescent lamp ballasts in parallel.
13:39 No worries, I’m already scared by just watching this video😅
The only real benefit to inverter based power supplies is powerfactor. That and it's less likely to kill idiots because they typically break before you can do anything silly with them.
I like fancy inverter stuff but only when schematics and stuff is available. Proprietary non serviceable designs are basically E waste
Please add a video about BLDC motor drives.
I think most intetesting for people are repairing battery powered tools like drill battery and their charger. I have made many repairs but not upload to my channel. Lets start together to share knoledge.
I have one, could not believe what I saw when I popped the cover off. Theyre probably all going to this ddesign. Id imagine its way cheaper
Can somebody provide some insights as to why the capacitors in the doubler circuit are different values?
This seems to be the case in every microwave inverter I've seen.
They are the same value in the older Panasonic Series 2 inverter I have in front of me, but later series certainly use two different values, usually when they are a single ended parallel resonant converter, which is not symmetrical in operation. The capacitors are resonance capacitors. Not simply energy storage for the power output, but a time constant in resonance with the transformer inductance, as is also the case with the much larger single capacitor in the mains transformer designs, them at 50 or 60 Hz, these at tens of KHz. I hadn't seen specific discussion of the capacitor values but I did find a technical document that covers it. Linking away from UA-cam is problematic due to rules, but if you search for "Parametric Design Guidelines for MW Oven Inverter" you should find it. If necessary add Bocchiola.
@@PlatypusPerspective thanks for the info!
@@MrTurboturbine Hope it helps. 🙂
Someone needs to petition to change the official IGBT schematic symbol to a little mushroom cloud in a circle. 🤪
Hopefully our 30 year old microwave oven without fancy electronics will last another 30 years so I don't have to buy this e-waste in disguise.
From the flux residue on the back, I can assure you the transistors have been replaced before.
Good old school transformers are the best. Semiconductors burn with a smelly fart in the presence of high voltage.
26khz pwm to activate the output is variable.