Usually microwave transformers provide up to 1800 - 2800 volts on the secondary side (output) If you apply 1VAC on the primary side (and your transformer is 240VAC in and 2800VAC out) you should read around 12VAC on the secondary side. But this is dangerous to do, so no attempt to make this happen, if something goes wrong you might end up trying to get your second life.
You can always use the reverse technique. Apply an A.C voltage in the secondary and see how much this voltage is stepped down in the primary winding. It is much safer for that matter and works perfectly!
@@user-pz6cx8zf2y I really appreciate your participation on this thread Question: If I feed PWM DC to the primary, would some current show up on the other side?
For Safety Never test live unless you're a trained professional and now exactly what you're doing, so if you're asking I'd say "No" Safety first look on Facebook marketplace before you light yourself up...
I have three switches on the GE microwave. Two of them are normally open and has similar specs like Gsm-v1603a2 250V. But one switch shows GSM-V0303A2 , which is hard to find. Is there a replacement for this one?
Hi - I live in a 240V country and I tested a 240V transformer, the primary was about 3 ohms dc resistance. And the primary wire looks thinner than yours, it is about 260 turns.
@@fuorman4872 Your comment is based on what? Mine was based on a measurement on the primary of a small 240V MOT. I also measured a larger 240V MOT, the primary dc resistance was 2 ohms. Nothing wrong with either of them, working fine.
@@fuorman4872 The video suggests dc resistance value for a 120V transformer as used in USA/Canada. But other countries can have different house voltages. I am telling you for the third time, my measurement is for a 240V transformer! That means the primary wire is thinner and longer. That is why dc resistance is higher. Also, do I really need to say that we often make a measurement at dc even if the transformer will be used with ac of course. Three ohms DCR is not 'bad' for a 240V MOT.
This was helpful. I can't tell you how many RU-vid videos I've gone through that we're not in English. I disassembled a bunch of coil packs or Transformers on a circuit board. Are these all Transformers. And are they just AC Transformers.
Hey great video! I was helping a friend fix her microwave by replacing the transformer and capacitor, as suggested by a friend. When i reassembled it and ran it the first time, it ran for 10 seconds then shut off. I took it back arpart and found I did not connect the white plug from the transforner into, whatever it goes into. My connector is a 2 wire, and bigger. It's an LG microwave. Any thoughts on what I did? I am thinking i fried both parts. Is it possible I damaged any other parts with this mistake?
If HV Transformer primary shows 3 ohms instead of 1ohm & HV taping to geoend shows 226 to ground, then is the transformer ok or not. Please guide. Primary is getting 220vac from control & Microwave not heating!!
Quick question when testing this thing I get like a 005 and I'm testing the bottom the bigger diameter wire does that mean it's grounding out cuz I have a brand new microwave Toshiba everything works but it don't heat so I'm trying to figure it out
Hi Friend. I,m from Brazil and I would like to get the resistance value of the secondary(High voltage). Something around 120 Ohms. Thank you very much. God bless you.
The resistance value of the windings of a transformer is not a safe way to decide about the health of that transformer. (Please see my answers to others in the comments of this video).
Yeah you need to go to an end where it isn't coated. I believe I said that in the video, but yeah you can't go over the coating. If you look on the edges you can find a spot where the coating isn't. Thanks for the post!
Symptoms. The microwave is working. But, when I open the door to remove a recently microwaved item the microwave light and fan (on low) sometimes come on. . Then sometimes when I press cook the microwave indicates it will cook. However, when I press start it will not cook unless I open and close the door and press start again,. So in both instances, it sounds like the door switches are at fault? I think I have one or more defective microwave door switches and the under the cabinet microwave is only 1.5 years old (model jvm3160df4ww): The access to the door switches is fairly far from the capacitator. Is it safe to test and replace the door switches without opening up the microwave to discharge the capacitor (which would high to the upper right of the control panel)? In other words, I would be far from the red wires connecting the capacitor and the transformer. If necessary, perhaps I could wear some sought of gloves that would protect me from shock. But once again, if I am far from the capacitor I think it would be a safe repair. I am trying to avoid removing the heavy microwave from under the cabinet. It is very hard to reinstall it once removed just to remove the inaccessible panels to discharge the capacitator. In the video you did not remove the microwave, you just removed the control panel and the grill, and then the switches. I would be more than happy to follow what you did as long as I did not need to discharge the capacitor.
Hi, asking for a solution here. Continuity test at the terminals feeding the capacitor showed 0 Ohm. Between one of the terminals and the chassis it was about 230 Ohm. The fuse was blown. Are these signs of a bad transformer?
Any reserve is stored in the Capacitor and in some it can last for a long time. The oval silver can looking thing. You need to discharge that. I did not watch this video, but it seems like it make be right from the title. It is not my video, so please be extra careful. I know a few years ago young kid in his early 20's was recycling microwaves and actually died. Best of luck and be safe... Hopefully this vid works for you ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-HES4LVQDvJc.html
In a mw transformer there are three windings. The first one (the nearest to the core) is the primary one. Next is the one with the red terminals in this video. This is a low voltage but high amperage winding for the heating of the filament of the magnetron tube of the oven. Next is the high voltage winding which feeds the anode of the magnetron. Both the filament and the anode feeding windings are the secondary ones, which are independent to each other. Moreover, the high voltage winding has its one terminal grounded. The other terminal, after a rectification and smoothing with a capacitor feeds the anode of the magnetron with almost pure d.c high voltage. I hope that your confusion is now gone!
@@christianstclaire5706 All the so called linear transformers work exclusively with A.C and (of course) reproduce (as a rule) in their secondaries stepped down replicas of their primary waveforms. M/W transformers also produce a stepped up replica of the mains. This is an exception of the usual applications. The high voltage is rectified just because it must be so. For the filament’s low voltage/ high amperage supply, there is no need for rectification. Filaments work happily with both AC or DC as they are resistive loads producing merely heat... What has to be kept in mind is that any such transformer should never be connected to D.C source. This is due to the fact that D.C does not care about the inductive impedance of the primary winding and “sees” only the pure resistance of the wire of the coil. Therefore, if connected in DC source, the transformer will immediately be blown up...
Those red wires are for the e-z-Pee-z "Ament" Engineer contacts. So much easier than using a multimeter. Totally sure you qualify; After plugging it in to the adapted 220 outlet, grab bare spot on the tip of the wire farthest to your left with your right hand, next grab the wire farthest to your right with your left hand at the same area as the first wire.... now... if you've felt a tingling sensation after everything goes black your windings should be good. You can now call the nurse over and request your discharge paperwork, head back home, and finish up that project you were working on... BUT- If you feel a tingling followed by an all encompassing warm, inviting, bright light, you might as well walk into it because whatever the result of the test it no longer matters. 😁😂😂 Cheers mate
what if the reading you get when measuring the high voltage is higher ie instead of getting a reading between 80 to 120 ohms, you get 250 ohms. what does it suggest?
I have two RCA microwaves that don't heat. I've checked everything and the only problem with both of them are their transformers with ohms over 200 ohms. I suspect that means the transformer is bad. But nobody seems to comment on this. So, I'm like you, Paddy: I'd like to know for sure if the ohms reading is above 120 ohms, does that mean it's bad?
I'm getting 148.5 ohms on the high side... Is that too high? ~( 'w')/ Also, if the related diode is good, will it have some kind of resistance on it one direction or the other and if so, about how much? I tested my diode and it seems to be like zero ohms regardless of polarity.
Question 120 ohms test from secondary winding to case shouldn't that be OL (infinite) reading. Is the secondary winding isolated from the case? I'm asking because I don't have a diagram of the transformer.
The transformer's secondary has one end connected to the transformer core as a neutral or live depending. The second wire with a connector for the capacitor is the other end of the secondary
Hello Sir, I get around 70 ome for the high voltage wire, for other wires I get same yours. Is my transformer bad or good? I have Whirlpool Microwave. Regards.
Not sure what you mean, but these may help ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-l4ZBJdxZjyw.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-i7MwYTvXGsI.html
This is useful only for the high voltage winding. (As regards continuity). For the rest two windings it is useful only for leakage tests, not for continuity.
If you type your issue into a search engine it almost always will tell you 1-3 possibilities. Then search youtube to see which one best fits your situation and then start there. Otherwise it's really tough to pinpoint an issue from thousands of miles away. Good luck with your machine...
This test proves only that the windings of the transformer are (roughly) intact. This doesn't mean that they are working as they should, because this test cannot prove that there are shorted turns, especially in the high voltage winding.
I am a beginner with enough electrical knowledge to dare to fix an old samsung microwave. I have just plugged it in and noticed there is no dc coming out of the transformer side that is connected to the front buttons. I think I should get an output of 12v dc. Is the transformer broken?
Captain Prototype Transformers work exclusively with AC voltages. That is, they are fed at their primary coil with the mains voltage and produce at their secondary coil the working voltage of the device. Now because electronics work on DC only, the secondary voltage of the transformer needs to be rectified by a diode bridge and smoothed by an electrolytic capacitor. This is the ordinary circuit in its basic form. If you suspect the (auxiliary) transformer, you have better verify first the continuity of its coils. For this purpose, have the apparatus unplugged (no power on it), and then check the transformer’s windings with your multimeter set in Ohms function. The primary winding should measure around one kΩ, whereas the secondary should measure only a few Ω, or less. If continuity is verified, then you should check the input and output AC voltages. Just because you say that there is no output voltage, the possibilities are: a) open fuse at the primary side of this transformer b) open primary winding c) shorted rectifier at the secondary winding. In this case, if there is a fuse at the primary, will be found blown. If there is not, the primary will be found open. Anyway if you find a blown fuse at the primary and it blows immediately after replacement, then there is a short circuit somewhere in the secondary side. If there is no fuse and the primary is open, then, before replacing the transformer, you must find what is wrong in the secondary that overloaded and finally destroyed the transformer. Otherwise the new transformer will blow as well...Good luck and keep your eyes open when working with mains voltages. If you don’t feel confident, let the job done by an expert. Anyway, the responsibility of your actions is all yours. Act accordingly!
Thanks for your answer. I can see I didnt know some important things about the transformer. I will try it with my blue rubber gloves on off course..Ps, I checked both fuses already.
@@user-pz6cx8zf2y ive just mesured the secondary coil. 3 ohm' that is perfect. Also there is contuinity between the contacts of the secondary. But i can only see one contact on the primary so i cant measure the primary windiing.. what can i induce about the fact that I also could not find any voltage in the secundary?
Captain Prototype It is important to verify that the primary winding is intact and it receives input voltage. Search to locate the missing contact (power off). Probably there is a fuse between it and the power input. There is no other way on troubleshooting this case. Just follow my guidelines and work calmly, with your Ohm meter and the power off. First you need to verify that the transformer is healthy and then that the power reaches its primary winding. There are no other shortcuts on this case. You can also work “backwards”, in a safer way. Identify that there is continuity (almost zero Ohms) between the terminal of the primary winding you already found, with one of the two terminals of the power plug. Mark this plug terminal. Then, do the same for the other terminal of the transformer, after you’ll find it. It should be connected to the other (unmarked) plug terminal. For these tests the power switch must be in ON position. By the way, confirm that the ground terminal is good as well, just for safety reasons. (Zero Ohms between the metallic case of the apparatus and the ground terminal of the power plug).
Just wondering how it is possible that we are getting higher resistance readings through the primary coil than the secondary when the primary is a thicker and shorter length of wire?
That depends on the windings, there are step up and step down transformers. Look those up and study, I have been away from this for a very long time and would not want to give you bad info
High resistance means 1 meter thin wire has more resistance than 1 meter thicker wire You have a misconception in your thought. So thicker wire can deliver more current hence less resistance, Hope this helps.
The other side of the secondary coil is connected to the laminates, or casing of the transformer, you can see the connection if you look closely on the other side near the top middle.
I tested my Samsung WB27X10910 secondary windings and only read 45 ohms (HV tap to case). The manual said it's 129.5 ohms +2%. My microwave won't heat and tripped the dedicated main circuit breaker. I am thinking the reduced resistance is causing too much current and causing the breaker to trip (although no blown fuses in the microwave) and the Magnetron TCO to cutoff to protect the magnetron. Is this correct and do I need to replace the HV Transformer? The HV Cap is good, the HV diode is good, the magnetron is good as are all of the TCO sensors. Door switches checked good as well. Thank you.
Daniel Kinder A low reading like that means you have shorted turns in the winding and the current draw will increase. That is probably why the circuit breaker is tripping.
If you still have the unit not thrown away...Remove all the transformer loads i.e. let the transformer secondaries unconnected. Install a 10 amp fuse in its primary. Feed the transformer primary and see if the fuse blows immediately. If it does, you guessed it, the transformer is bad.
I am a beginner with enough electrical knowledge to dare to fix an old samsung microwave. I have just plugged it in and noticed there is no dc coming out of the transformer side that is connected to the front buttons. I think I should get an output of 12v dc. Is the transformer broken?
Hey thanks for your cool video. The resistance between the input terminals is fine, but when I check the resistance of the 'output' terminals that feed into the capacitor... they reach infinity. I'm wondering if that means my transformer is the issue? Any thoughts? Thanks
Check first if you are using the correct range of your multimeter. Then make sure that you are measuring across the coil of interest. If you are correct on that, an open circuit means a faulty coil (no voltage output).
Tested the primary resistance and getting a floating reading between .2 - .4 (sometimes hits up to .5). Video suggests .5 - 1.5, below 2. Is this a sign of a bad transformer?
or bad connections in your test. Or you meter leads something is causing the float. If its not you leads, meter, or your test connections, then whats left.
Around about the same resistance range as the as the 110v transformer. The output voltage range is also similar. The output voltage is then connected to a capacitor which has a diode connected to ground to effectively double the voltage
Any answer in this question will be wrong. The resistance of the primary winding (for the secondary the same thought is valid as well) depends on the number of turns of the wire used, that is, its length, the material of the wire (copper or aluminium) and the diameter of the wire. In turn, the diameter has to do with the primary current, the number of turns with the primary voltage whereas both of these parameters have to do with the nominal power of the transformer core. Therefore any answer without any other reference is faulty in advance. Only comparison numbers can be given in reference to one specific transformer, having a given nominal power. In other words, among many transformers having the same construction, a working one of them can be used as a reference for the rest of them (with very tight tolerances as regards the comparison of their Ohmic values of their respective windings). Still the question of shorted turns remains open.
My GE Profile Microwave worked for about 5-7 seconds then shut off. Further exam revealed burning/sparking in HV Inverter/Transformer. Digital continuity checked OK for all door switches, primary thermostat, shut off fuse, etc. Replaced Transformer with new part. Everything worked fine except 'No Microwave Heating'. Next, replaced Magnetron and Relay Switch on the circuit board. Everything worked fine except 'No Microwave Heating'. Magnetron humming seems normal! Cleaned mica wave board inside of unit, no sparking here. Can anyone advise what the problem may be. Again, everything worked fine including settings for time, power levels, clock, etc. when started up except 'No Microwave Heating'. Last resort before dropping out to the curb for the landfill! Any ideas greatly appreciated! HELP! Show less Reply
If you still have the unit not thrown away...No heating means "magnetron not working'. This in turn means a) no high voltage for its anode supply. Then, a1) break in the high voltage circuit, a2) open high voltage fuse a3) open high voltage rectifier diode a4) open or shorted high voltage capacitor (depending on the diode behaviour or fuse status). B) no low voltage- high current supply for the filament of the magnetron. C) excessive leakage within the tube. Anyway, chances are that you missed something in the high voltage circuitry which is a common offender.
great video, but your wearing a ring and your also measuring your own body resistance in parallel with the transformers resistance...which will drop the Rt significantly...simply do not touch the leads with your fingers...I suggest clamps
If you are measuring a low resistance wire you don't have to be worried about it, your resistance is insignificant to the measurement. Make the calculation, 2 resistances in parallel, one higher another way lower, the lower wins the biggest percentage of the value. Like that wire and your body skin. Something he did wrong was that he didn't measure the resistance of the probes, that usually is around 0.2 up to 0.7 depending o the quality of the Chinese material What do you mean with the ring?
@@FixDaily He probably means the risk of electrocution (which is not there when the device under test is not powered). Exaggerated sense of safety I guess...
You must zero out your multimeter!!!!!!!! when you measured the short secondary winding that read 0.8ohms that's the resistance of your leads!!! the true resistance reading of that winding is almost zero ohms, it's like 0.04 ohms because it's a very short winding like 2m long. I had to find this out the hard way and open up the transformer all for nothing. it's NOT 0.8 OHMS!!!!
I have heard that a MOT is capable of putting out around 2000VAC 5A 10KW. My advice is to research it for yourself so that way you'll know for future reference. I hope my comment has helped you. Please, always SAFETY FIRST. Those MOTs and their capacitors can kill you faster than a Jackrabbit on a date. Peace, out.
I'm getting the same thing on mine. I ordered a new transformer. Hopefully this is the problem. I see this guy is yet to reply to you. Did you get anywhere with your problem? Thanks
Any continuity reading of a winding is an indication of a good winding (as long as the reading is not zero Ohms or nearby). This test cannot detect shorted turns of the winding under test. Any resistance measurement of one terminal of either of the windings against a) the core of the transformer (or (b) against the other winding) is an indication of either a leaky (bad) winding (case a) or of a short between the windings (case b).
@Racist Brownie I forgot to mention that in order to test the transformer (any linear transformer) for shorted turns you can use a small incandescent lamp (say 40Watt) in series with the transformer, with no load on it (all secondaries disconnected). If you feed the transformer with that lamp in series to its primary, the lamp should NOT glow. If it does glow, the transformer has at least one shorted turn somewhere in its windings...
Another way to test this transformer ( safety ! ) is to put your mains across the HIGH VOLTAGE coil ... then you should read a VERY low voltage coming from the side normally connected to mains ( for UK 230 Volts this might be around 20 Volts ) the USA transformers should be slightly lower Voltage ( ? ) if it does not get hot or smoke then the transformer should be OK .... NEVER ! test with mains connected to the correct winding ( you WILL die ! ) ....... DAVE™🛑
This test gives only an indication that the windings of the transformer are (or are not) open. But still the question of good operability of the transformer is open, because this test misses the problem of shorted turns in the windings.
@@christianstclaire5706 You don't need any load for that purpose. Generally speaking, for any linear transformer used in electronic appliances, just disconnect all its secondaries and have the transformer loadless. Then connect it's primary to the mains. A heavy short anywhere within its windings, mostly in the primary but also in this case could be in the high voltage one for the magnetron anode, will immediately blow the primary fuse. If it is not fused, the transformer will rapidly develop excessive overheating in both its core and windings. Needless to say that one must be very careful where performing such tests, especially as regards microwave oven transformers, due to their high voltage being always present in their relevant winding!!! As a rule of thumb, any of this kind of small transformers is to be suspected for shorted turns if when left loadless is connected to the mains for one hour happens to develop a core temperature of more than 50 degrees Celsius. This is a general indication that "something is wrong". A more practical method for identifying this type of failure (shorted turns) is as follows. A) First of all, it is good to know in advance the power of the transformer to be tested. B) If it's power is, say 250 Watt, we take an incandescent lamp of smaller power, say 40 Watt and connect it in series with the primary winding, before connecting the transformer to the mains. C) We connect the circuitry to the mains, while watching the lamp. D) If the lamp glows, there is definitely a short somehere there. If the transformer works normally, the lamp behaves like not being connected anywhere. That's all...
It's the high voltage capacitor that the transformer is hooked up to that can kill you, it stores energy like a battery but releases it all at once. It's a cylinder shaped piece that looks like a battery, take a screw driver with a plastic handle and arc the terminals to discharge it, and be careful.
Depending on the cost of your machine or if you need to save it to fit in a certain space or color many like to purchase a new mwave. Here is a link to check out; www.mrright.in/ideas/appliances/microwave/4-common-reasons-of-sparking-inside-microwave/ is it sparking in the microwave or is the magnetron actually sparking?
What if all my readings are higher? Like main coil is 3.4ohm and not 1.5, resistance of the secondary is 190ohm instead of the 120 in the video? No continuity throughout the body though
