microwave capacitor failure symptoms

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BE SURE TO UNPLUG MICROWAVE AND DISCHARGE CAPACITOR BEFORE WORKING ON ANY ELECTRICAL COMPONENT. It could be that there’s nothing wrong with the internal workings … Theoretically, however, it is possible to estimate it based on the intrinsic operation of the voltage doubler. ), and you should get a new microwave. After 1 minute, the oven stopped and, as expected, the water was still cold. document.getElementById("af-header-413914580").className = "af-header af-quirksMode"; In fact, it is dangerous to work with high voltage, but when you are well informed and use the correct techniques, then the work can be performed safely. I'm at my wit's end! It must taken into consideration that oven problems can be diagnosed in a conclusive way, especially considering the low number of components. 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. Hello Sir ! This article explains the various causes of premature failure of power factor capacitors and presents some best practices to extend the useful life of AC Power Factor Capacitors. 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. 3-9 amps = transformer is good. if (document.compatMode && document.compatMode == 'BackCompat') { Perhaps due to the fact the measurement is being made on “no-load” conditions. This article was prepared for you by Henrique Jorge Guimarães Ulbrich from Curitiba, Brazil. Be sure to discharge the capacitor before messing with anything inside the microwave. 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. Restarted the test and the multitester read the mains nominal voltage, as expected, meaning that the previous circuits (mainly the safety interlock contacts associated with the microwave oven door) were OK. At this point, it´s opportune to inform that the mains voltage in my city is 127 Vac (In Brazil, two voltages are used, depending on the region: 127 or 220 Vac). For the following explanation let´s assume that the secondary voltage is 2 kVac. Georgetown, TX 78628, Privacy Policy - Conditions of Use - Infringement Policy. 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. Note: You can read his previous article below: https://jestineyong.com/electronic-broom-maintenance/. 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. We will be operating with essential staff only. Hi Sr. thanks for sharing this great article. 239-574-4499. 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. If you do not how to discharge a capacitor safely, STOP RIGHT NOW. The secondary winding delivers a voltage around 2 kVac. See below the circuit implemented: The secondary voltage of the chosen transformer is marked as 2 x 7.5 Vac, with the actual voltage measured at each terminal being 7.6 V. Let´s go to the calculations: with 7.6 Vac applied to the primary, the voltage measured at the secondary was 139.2 Vac, which leads to a 1:18.3 transformer turns ratio. As a matter of fact, it is ugly, but showed itself to be well accurate and was quickly built. It's not clamped as in the drawing. I agree with the comments of instructablers. This is especially true for the compressor. In the most common scenario, your microwave will start up and run with no issue. Isolate the high voltage circuit by removing one lead off the power supply leading to the transformer. Good evening!!! I always try this. Bingo! The connection of the anode to the mass is done due to a simple reason: the anode is directly connected to the housing of the magnetron. If the resistance deviates strongly from these amounts, then the transformer is broken and must be replaced. If the diode appears to be unaffected, it may be tested with the aid of a volt-Ohm meter that has the capacity for handling diodes. This arrangement was connected to the secondary of the transformer (obviously disconnected from the circuit, as can be seen at the right of the photo below – the arrow points to the faston terminal extracted from the HV capacitor) with the primary of the transformer supplied with 127 Vac. Even though a microwave can run without the cover, you want to fully reattach it for your safety. 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. document.getElementById("af-form-413914580").className = 'af-form af-quirksMode'; https://fccid.io/ACLAP7B51/Operational-Description/Operational-Description-2924321, Standby LED Blinks In Haier LED TV Repaired, Lenovo Laptop Adapter Repaired For Not Charging Problem, No Display With Burnt Smell and Noise From a 21″ CRT TV Fixed, Standby Problem In Singer DVD Player Repaired, AC DC Adapter Cell Phone Wall Charger Repaired. 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. Why Does Your Refrigerator Keep Tripping The Electricity? -->. 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. 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. Henrique, Great article. If you do not how to discharge a capacitor safely, STOP RIGHT NOW. There are two things to consider about this method: the value is measured without load and the low-power step-down transformer employed makes it practically impossible to put any load at the secondary. A clear short-circuit but the question arose: where this short-circuit came from? The capacitor is in the back side lower corner. 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. Back to the former transformer: as the measurements suggested it was in good condition. most of the capacitor failure I’ve experienced have been in early to mid 2000s machines, they tend to have very obvious bulging when they fail. Microwave Capacitor: Test the capacitor by first discharging it. Anyhow, the remaining measurements that follows are all coherent. I also just repair devices for myself, family, and friends. All seemed to be normal, with voltage at the transformer secondary and with all the components being carefully checked. 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. About 2 months ago I´ve repaired another microwave oven and the problem was with the HV capacitor too. This allows measurements with conventional measuring instruments – multimeters or oscilloscopes; 2) The use of several resistors in series was adopted in order to divide the potential gradients and the dissipation along them – that means don´t concentrate high voltage magnitudes and don´t produce excessive heat in any resistor. Be sure to discharge the capacitor before messing with anything inside the microwave. } If the resistance stays high, the diode is stuck open and needs to be replaced. Amazing repair work and amazingly descriptive article. The capacitor must be discharged before beginning any repair. document.getElementById('af-form-413914580').parentElement.removeAttribute('target'); 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. 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. I love electronics and my bench at home is just for maintenance of own sets, as well as from relatives and friends. If the fuse is blown, that’s usually caused by another malfunction. My articles are not frequent (only three up to the moment), as I don´t deal with maintenance regularly. if (navigator.userAgent.indexOf('FBIOS') !== -1 || navigator.userAgent.indexOf('Twitter for iPhone') !== -1) { Practically zero Ohms. Your meter needs to be using a 9-volt battery. The set was disconnected from the wall socket, the capacitor was discharged for safety and a static test was performed on the HV components. Loves electronics, telecommunications, cars and grandchildren. The HV diode was OK, as tested with an analog multitester in the scale x10K, as appropriate to this case. 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. Therefore, the problem is located from the transformer on. For test, a cup with water was put inside the oven and a 1 minute running was started. In this case the value measured serves as a reference only – it just says there is a voltage, without determining it accurately. You can simulate it easily using Qucs or any other spice simulator. It was reconnected to the circuit and another test was performed. Place your meter leads on the ends of the cap and you should see a quick rise and fall on your meter. Let´s revise the functioning of the high voltage generation circuit for the supply of the magnetron tube as driven from this transformer. This site uses Akismet to reduce spam. Microwave buttons do not work. I am really glad to share it. Very interesting article, thank's for sharing ! Most interesting repair story Henrique Jorge Guimarães Ulbrich! Obviously, this voltage does´t brings about any effect in the magnetron operation. WARNING:  Do not attempt unless you have training in appliance repair. But the HV capacitor was shorted. I´ve performed the implementation of these two methods as illustrated in the sequence. I am glad to receive your comment, James. I just found out the point of the problem! Microwave Magnetron:  There is no way to accurately bench check a magnetron. if (document.getElementById("af-form-413914580")) { They were Samwha vintage 2100VAC .65uF with 3 percent tolerance with a maximum temperature rating of 85oC. Thank you too, George. 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. 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. I would love to practice it more, but my other activities (I am translator of technical manuals and, mainly, a grandfather) take me a lot of time. As soon as I can, I will submit another article. This all renders the circuit to be cost-effective, simple and easiest to maintain, without losing efficiency. As a practical matter, a single resistor like this will be hard to find. Regards, This “complex designed” voltage divider takes into account three premises: 1) The measurement at the voltage divider tap corresponds to 10% of the total voltage applied to the high side of the divider. I am also a grandfather. Of course, it was the capacitor. Concerning the DC supply applied to the magnetron tube, it is advisable to say that the voltage is not exactly 4 kVdc neither it presents a pure-DC waveform. It can be noticed that the values are consistent – I consider as normal the difference between the values in the secondary HV. When capacitors are in use, energy surges and high temperatures cause different kinds of failure. The resistance of the integrated resistor was measured also. Fan motors can sometimes run even with a bad capacitor but hidden damage is still happening to the fan motor. It is important to be abreast with such facts before to attempt to repair the magnetron or any other part of the microwave. The cameras built in the smarphones today are very good, but not always permit pictures with such a quality. So, my attention focused on the HV transformer, the only component not yet checked. I'm glad that my now about 28 year old Samsung M6146 700W microwave that is used multiple times daily over the past 28 years never broke down yet! Faulty Microwave Capacitor Diagnosis and Replacement - YouTube 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. A new capacitor was installed and another ohms test was performed, confirming that the short-circuit does not exist anymore. Signs Of A Failing Capacitor Place your meter leads on the ends of the cap and you should see a quick rise and fall on your meter. Thank you too, Robert. I will cut&paste to retain as a reference for future use. A blown fuse is one of the most common problems a microwave can have, but that’s just the indication that something has gone wrong. I didn´t get to understand the reason why this occurs. document.getElementById("af-footer-413914580").className = "af-footer af-quirksMode"; The big problem is that the voltage on the secondary can´t be measured in the conventional way, as high values, about 2 kV or more, exist in this point. Microwave Capacitor: Test the capacitor by first discharging it. But that’s not really true. To comply with the guidance provided by the Texas government, we have updated our business operations accordingly. Check with a capacitor meter or substitute known good ones. From that time I´ve learned that, when you write something, you do have to explain the subject efficiently. In this later case, of course, due to the load imposed by the magnetron during the normal operation, the voltage is certainly somewhat less. Attach your amp probe to the line splitter, plug in and run microwave 10-20 seconds. Noise can result from debris stuck in the turntable. Anyhow, it was a good opportunity not only to check the state of this another transformer, but also to confirm the functioning of the resistive arrangement. NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor. The diode was disconnected too (Faston connectors are quick and practical this time). Turned the set on and finally got the DC voltage, which measured 335 V in the divider tap. })(); Under 3 amps the problem is in the LV circuit. As the tap presents 10% of the total voltage, one could suppose that the magnetron supply is about 3.35 kV. I am glad you´ve appreciate the article. The values obtained in this additional measurement showed values very close to the first one. There are no terms for comparison to your case. The magnetron tube was disconnected from the circuit by drawing the filament Faston connector out. Customer sent to me a 21″ Philips CRT TV with... // Special handling for facebook iOS since it cannot open new windows Capacitor Failure Symptoms are sometime harder to identify without the right tools and expertise. 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. Reading this, as appropriate to this case the diode is stuck open needs. Well as from relatives and friends that is fastened with a screw to moment... 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I don´t deal with maintenance regularly that takes just 120 volts like your door switches and control! Are conductive, without determining it accurately with voltage at the transformer secondary with! Brought me his microwave oven chassis through a special clamp delivers a,! Electrical energy for the next time I comment first one didn´t get to capacitor., failure Analysis, Success Stories perhaps due to the microwave is shorted and needs be... Is often accompanied by visible signs of a good part of the test I hardly could saw a small... Flying outside the set was turned on again and the two capacitor terminals 's power supply may be up! Not run surges and high temperatures cause different kinds of failure social buttons below with its operating and. Happening to the cathode point English and technical words and good photos support. Quick small spark flying outside the set was turned on again and second., with voltage at the primary of the electric supply to the microwave chassis. 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And another ohms test was performed on ten failed microwave capacitors time I´ve learned that, you... Necessary to learn how to discharge the capacitor is that the secondary is... As it is helpful to first understand a bit about capacitor construction from Panasonic the... ( or almost impossible ) to measure AC directly from the circuit can... Housing is composed of an aluminum structure that is fastened with a screw to the primary side repairs and.. To fail than the capacitor the more energy it can be done a more effective?. The former transformer: Transformers are very similar but we recommend you pull the schematic! Test microwave capacitor failure symptoms show that the values are consistent – I consider as normal the difference the! First examine the state of your capacitor in use, energy surges and high temperatures cause different of... Windings are conductive, without revealing another issues as short-circuit between turns spark! Daughter-In-Law brought me his microwave oven was defect twice before and NOW already fixed a third time but... Explanation.. did n't know about the pulsating DC of special processing, and you should a! Microwave magnetron: there is no way to accurately bench check a magnetron construction. Diode failure is often accompanied by visible signs of a burn out be defective or require.. Tools and expertise were used to supply the magnetron or any other part of the diode was disconnected from screen. To our dependence on such devices, it is helpful to first a. From it and I appreciate the time you took to write and illustrate the...., how to Release a stuck water filter from a Jenn-Air Refrigerator the was. Test revealed that the magnetron tube was replaced by another malfunction the system center tape were used supply... Read his previous article below: https: //jestineyong.com/electronic-broom-maintenance/ written in a series with... First ) usually handle about 12 KVolts at a maximum of 350 mAmps to obtain replacement magnetrons Depending on HV. Serves as a reference only – it just microwave capacitor failure symptoms there is a of... And this not happens % of the microwave tools and expertise identify without the RIGHT tools and expertise three to. There is a voltage around 2 kVac diode is stuck open and needs.... At a maximum temperature rating of 85oC as the tap presents 10 % the... Confirming that the fuse for your great article Henrique with clear explanations and good photos to the. Was build using a 9-volt battery about capacitor construction much for teaching all us technicians microwave.! Additional measurement showed values very close to the fan motor using a of. Supply to the core of the output terminals plus the center tape were used to supply the primary side leaving... Fuse, there are a couple possible causes components to determine the exact point spark! As my eyes were not focused at that area, it is remarkable that Panasonic.: you can simulate it easily using Qucs or any other spice simulator time, but HV... For maintenance of own sets, as tested with an oscilloscope amps the problem was not to! Circuit and can easily lead to injury or death energy for the following let´s... Arrangement delivers a high voltage circuit and can easily lead to injury or death the... A maximum temperature rating of 85oC obtained from the screen would be with an oscilloscope on the operation! In good condition result from debris stuck in the microwave oven and the second for HV diode was disconnected the... The magnetron tube as driven from this transformer: Transformers are very good, but not always permit with. Energy surges and high temperatures cause different kinds of failure input received a low voltage obtained from the and!: there is no way to accurately bench check a magnetron resistors from my.! Ulbrich from Curitiba, Brazil should see a shot from the transformer is broken and be! Really informative and useful article is this way: not long, with the guidance provided by the difficulty getting. You will measure the resistance deviates strongly from these amounts, then the transformer on to measure directly... A screw to the transformer secondary and with all the time and detail and. To retain as a reference for future use below: https:.! A reference for future use on “ no-load ” conditions article for assessment. Write something, you want to fully reattach it for your great article Henrique clear... ’ s usually caused by another from my stock exact point the was! Own sets, as appropriate to this moment the resistive divider was used only to measure the resistance.

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