Use a resettable fuse before testing so you don’t run through new fuses while testing primary malfunctions, but you can test with new fuses if that is more convenient. Good evening!!! if (navigator.userAgent.indexOf('FBIOS') !== -1 || navigator.userAgent.indexOf('Twitter for iPhone') !== -1) { As my eyes were not focused at that area, it was not possible to determine the exact point the spark was generated. For the high voltage capacitor in a microwave oven, use a 100K ohm resistor rated at least 5 kilovolts and several watts for your discharge widget, with a clip lead to the chassis. Hello Sir ! A blown fuse really means one of your electrical components has broken or failed, and the next step is to find out which piece that is. Just as most homes are equipped with fuses or circuit breakers, microwave ovens also have fuses that short out or blow in the event of an overload. So the correct connection to ground is obtained by a secure fastening of its body to the microwave oven chassis, using a number of screws that must be efficiently fastened. Your email address will not be published. Your email address will not be published. Thanks, Tony. The values obtained in this additional measurement showed values very close to the first one. Then use gator clips to put the diode in a series circuit with the battery to test the voltage. Customer sent to me a 21″ Philips CRT TV with... // Special handling for facebook iOS since it cannot open new windows The higher the capacitance of the capacitor the more energy it can store. It is useful to build the probes with good quality suitable alligator clips (never forget to discharge the capacitor first). When I applied the probes of the ohms tester between the chassis and one of the capacitor terminals (those connected directly to the magnetron), the short-circuit became evident. This all renders the circuit to be cost-effective, simple and easiest to maintain, without losing efficiency. An appropriate measuring would be with an oscilloscope on the tap. Opened the oven. Hi, Dear Henrique, So, make one up from a … A clear short-circuit but the question arose: where this short-circuit came from? I didn´t take shots of this, as it is not directly relevant to this present maintenance work. After taken the capacitor out the chassis, another definitive test revealed a resistance of 23.7 Ω between the casing and one of the terminals. My articles are not frequent (only three up to the moment), as I don´t deal with maintenance regularly. Replaced the cup with water inside and set again the operation to 1 minute. We will be operating with essential staff only. For test, a cup with water was put inside the oven and a 1 minute running was started. In this measuring method the step-down transformer above is not used anymore – the normal transformer connection is maintained, with the mains voltage being regularly applied to the transformer primary through the existing circuit of the set under repair. During this time, as the diode is forward polarized, there is no voltage supply to the magnetron – only the very small forward voltage of the diode, that´s insignificant for magnetron operation. Perhaps due to the fact the measurement is being made on “no-load” conditions. Please give a support by clicking on the social buttons below. After 1 minute, the oven stopped and, as expected, the water was still cold. An ohmic resistance test was done in each winding, resulting OK. As a matter of fact, it is ugly, but showed itself to be well accurate and was quickly built. The magnetron tube was disconnected from the circuit by drawing the filament Faston connector out. The magnetron is more likely to fail than the capacitor. Anyhow, the remaining measurements that follows are all coherent. document.getElementById("af-form-413914580").className = 'af-form af-quirksMode'; Another 1 minute test revealed that the problem was not resolved yet – the water in the cup remained cold. For the following explanation let´s assume that the secondary voltage is 2 kVac. } -->. You only can do measurements in the high-voltage sector  if you consider yourself a well prepared engineer or technician, and fully aware of the risks involved. Microwave buttons do not work. I didn´t get to understand the reason why this occurs. sorry for replying this old post, but the behavior described above is not completely correct. document.getElementById("af-footer-413914580").className = "af-footer af-quirksMode"; Obviously, this voltage does´t brings about any effect in the magnetron operation. This approach leads to some features: increased safety, avoided possibility of arcing, distributed dissipation and the possibility to improve the selection of resistors to be combined aiming at getting the correct values using existing resistor in the workshop, and. Even so the problem continued. The capacitor housing is composed of an aluminum structure that is fastened with a screw to the microwave oven chassis through a special clamp. In this helpful article, you will find out: what a motor capacitor does, the two main types of motor capacitors, and how to tell if your motor capacitor is bad. Coming back to the transformer. Your meter needs to be using a 9-volt battery. The isolation values between winding were also measured, resulting OK too. This needs to be checked on both ends of the diode, and it should only rise from one end since diodes only allow electricity from one direction. For mechanical timers, the timing motor could be defective or require lubrication. How then can be done a more effective test? High energy. })(); Hence the magnetron tube is, as a matter of fact, supplied with a DC pulsating voltage at 50 or 60 burst per second (depending on the line frequency – 50 or 60 Hz). Many single-phase compressors require a start capacitor to assist in starting the motor. Your meter needs to be using a 9-volt battery. The mains voltage is applied into the primary side. I agree with the comments of instructablers. BE SURE TO UNPLUG MICROWAVE AND DISCHARGE CAPACITOR BEFORE WORKING ON ANY ELECTRICAL COMPONENT. If the resistance never changes, the capacitor is shorted and needs replaced. A visual inspection revealed a burnt spot that can be seen in the photo below: This time I finally discovered the point the spark had been vomited outside the microwave set in the beginning of the troubleshooting. Oh! How to Replace Your Samsung Icemaker When It’s Not Making Ice, How to Replace Your Refrigerator Gasket Seal. The voltage doubler described above, in fact, is only a voltage "shifter", that moves the entire AC sin wave "as is" outputted by the transformer. I just found out the point of the problem! Microwaves can have 2000 volts of electricity in the high voltage circuit and can easily lead to injury or death. (function() { (adsbygoogle = window.adsbygoogle || []).push({}); I prepared the multimeter and connected it to the primary terminal of the HV transformer. There is only 1 diode in a microwave. At this point I had the inspiration to measure the resistance between the output of the voltage doubler (the joining of components mentioned above) and mass, obviously performing again the discharge action in the capacitor. As soon as I can, I will submit another article. Because of this, the measurement is done in a condition near the open state of the output, which tends to increase the value of the voltage being measured, mainly on the DC measurements, as will be seen further on. Additionally, our technicians are implementing enhanced safety measures to adhere to social distancing and sanitization guidelines issued by the government in order to continue providing safe and professional service. I am glad you´ve appreciate the article. I initially supposed it could be the HV transformer, but I wasn´t sure. From that time I´ve learned that, when you write something, you do have to explain the subject efficiently. The implementation of this voltage divider and the photo of it can be viewed below: Obviously this building is not the “wonder of the century”. Henrique, Great article. Cape Coral, Fl 33990. Theoretically, however, it is possible to estimate it based on the intrinsic operation of the voltage doubler. In this later case, of course, due to the load imposed by the magnetron during the normal operation, the voltage is certainly somewhat less. Loud noises such as bangs, buzzes, rattles and knocking while the microwave is in operation could indicate several things. Not everybody knows this, but the truth is: when activated, the magnetron does not work continuously – it works only half the time programmed in the front panel. Other aspects to note are: only one diode and only one capacitor are used; and the use of a voltage doubler means that the secondary of the transformer needs only half of turns. if (document.getElementById("af-footer-413914580")) { Even though a microwave can run without the cover, you want to fully reattach it for your safety. The total voltage applied to the magnetron is a sum of two partial voltages obtained in each half-cycle of the AC wave delivered by the transformer secondary. To finish the repair work I removed my “complex designed” voltage divider and reestablished and checked the complete circuit, confirming that all was correct. Microwave High Voltage transformer:  Transformers are very similar but we recommend you pull the wiring schematic to locate what wire does what. P.S-  If you enjoyed reading this, click here to subscribe to my blog (free subscription). I became very confused. If you do not how to discharge a capacitor safely, STOP RIGHT NOW. document.getElementById("af-body-413914580").className = "af-body inline af-quirksMode"; Microwave Capacitor: Test the capacitor by first discharging it. NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor. Here’s how: What do you do know that you know the inline fuse is blown? And if it blows the fuse for your kitchen, there also is a likely cause for that. Probably because your Samsung microwave oven does not use chinese components! If the fuse is blown, that’s usually caused by another malfunction. Here’s how to discharge microwave capacitor in three simple steps: hide 1 Checking the charge 2 Using a screwdriver 3 Making a capacitor discharge tool Microwaves have capacitors that store excess electric energy, especially when there is a sudden power discharge or surge. Required fields are marked *. WARNING 1: to everyone that decide to build the voltage divider describe I recommend to mount it in a circuit board and protect the circuit with an appropriate insulating housing. Microwaves can have 2000 volts of electricity in the high voltage circuit and can easily lead to injury or death. https://technoboy.wooplr.com How to test microwave HV capacitor using multimeter/ good vs bad Thanks for your comments, Mason. Practically zero Ohms. Most interesting repair story Henrique Jorge Guimarães Ulbrich! I unplugged the female Faston connectors at the primary side, leaving the male ones in the transformer free. Another point is the heat generated by the resistors: I noticed that they got heated up a bit, so the dissipation of these components shall be properly calculated in a circuit envisaged for constant use. When I applied the probes of the ohms tester between the chassis and one of the capacitor terminals (those connected directly to the magnetron), the short-circuit became evident. Thanks, Albert. if (!IE) { return; } Thanks. It thus converts the 60Hz supply voltage into usable microwave energy. This verifies that nothing that takes just 120 volts like your door switches and electronic control is causing the issue. If the microwave buttons do not work it indicates that the touch-pad … I imagined two different forms for testing it, both easy to perform at the bench: Any of these two methods bring an additional advantage: either of them allows the discovering of the transformer turns ratio with considerable accuracy. It was reconnected to the circuit and another test was performed. (function() { I have been reluctant to work on microwave ovens due to the lethal high voltages, but thanks to your safer test techniques, I will start to work on them for customers. Whether it is shorted or open, a defective diode will most likely show some sign of defect. if (document.getElementById("af-body-413914580")) { I love electronics and my bench at home is just for maintenance of own sets, as well as from relatives and friends. […] It's not clamped as in the drawing. There are no terms for comparison to your case. The HV diode was OK, as tested with an analog multitester in the scale x10K, as appropriate to this case. You can also forward this website link to your friends and colleagues-thanks! * The low side of the HV secondary is connected to the core of the transformer. Very interesting article, thank's for sharing ! Thanks for sharing. However, this type of test only show that the windings are conductive, without revealing another issues as short-circuit between turns. Learn how your comment data is processed. If your microwave oven blows a fuse, there are a couple possible causes. But the HV capacitor was shorted. 3)  The burden load to the high-voltage circuit is very small. I´ve performed the implementation of these two methods as illustrated in the sequence. Save my name, email, and website in this browser for the next time I comment. In my case, since the microwave oven has stopped working and unplugged power for a long time and there is one discharge resistor in the circuit, so I didn't show the discharge steps. Diode failure is often accompanied by visible signs of a burn out. Once the power is back on, test it by microwaving something like a small bowl of water or anything that lets you easily test the heating power. To comply with the guidance provided by the Texas government, we have updated our business operations accordingly. The analysis was performed on ten failed microwave capacitors. I also just repair devices for myself, family, and friends. Common microwave problems and faults and how to fix them The microwave oven has to be one of the most popular household appliances ever devised. Anyhow, it´s a reasonable evidence of the transformer condition, that showed to be good in this case. })(); The resistance of the integrated resistor was measured also. ... there are a few motor capacitor failure symptoms you should look out for. How to Release a Stuck Water Filter from a Jenn-Air Refrigerator. Of course, it was the capacitor. A visual inspection revealed no problem. This site uses Akismet to reduce spam. Appliance ExpressAugust 23, 2017Microwave RepairLeave a Comment. Hi Sr. thanks for sharing this great article. When capacitors are in use, energy surges and high temperatures cause different kinds of failure. Symptoms to Observe When a Magnetron is Failed: No heating Burning smell Arcing sounds Snapping sound Many of these type diodes are common in the lower powered Microwaves. This is a legacy of a good part of my past professional life, where I dealt with technical training in telecom area. The cameras built in the smarphones today are very good, but not always permit pictures with such a quality. Thank you too, George. Thank you, Henrique, for your excellently written and informative article! The diode was disconnected too (Faston connectors are quick and practical this time). Such a measure involves two aspects: by the difficulty in getting a meter for this voltage magnitude and by safety issues. I had already repaired it twice – one for magnetron replacement and the second for HV diode replacement. Note that in this case the arrangement of the magnetron circuit is unusual as compared to conventional electronic tube circuits: the anode (positive side) is connected directly to mass (ground) and the cathode (negative side) is under potential in relation to ground. In the next half-cycle the diode is reverse-polarized and the AC voltage delivered by the transformer secondary (2.8 kVac peak) is summed up to the existing voltage already charged in the capacitor, keeping the same polarity orientation and developing a 5,6 kV pulse that is applied to the magnetron. The front display became lit, indicating that the fuse was OK. You are welcome, Beh. Lately I’ve been tracking down troublesome capacitors in the vertical deflection circuit of a mid-80s 14″ CRT I own, visually they look ok and the symptoms appear to be a loose connection. From there, you will measure the proper resistance for each line when the microwave has no power. 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