When you checked the transformer, I think you only checked the input primary winding resistance, and the 3v low voltage winding resistance for the magnetron heater element. The last wire on the secondary side of the transformer is the output for high voltage, and the other end of that winding is bonded/riveted to the core of the transformer, so do the ohms test between hv output wire to transformer core to confirm hv winding is intact. It's also a good idea to test all windings for shorts to the transformer core. You can check for shorts in the primary, and low voltage secondary to the core fairly easily, but you'd need to disconnect the /riveted/bonded terminal for the hv winding at the core to test for internal shorts in the winding, or to the core.
Thanks in advance for taking the time to make useful videos and providing guidance! I have an LG microwave lcrt2010st or lsrm2010st installed Dec 2014 (looks very similar to the one in your video. Recently it has been start on its own when door closed, sometimes says door not closed when it is closed, kinda spooky! I was going to replace the 'door switch', but thought I should probably do a bit more investigation prior to ordering parts. My other thought is that the 'touch panel' could be flaking out since it will sometimes start before I have fully specified power level and pressed start. Any input appreciated!
That is a tough one. Sounds like maybe a bad keypad for starters. The door switches could be bad as well. Get a schematic and use it to test the door switches with a multimeter. Not sure how expensive a new keypad would be, but it might be worth changing out as a first step in troubleshooting. Scour the curb on trash day for microwave ovens, you might find parts for yours.
LG SmartInverter model Everything works normal but stopped heating food. Only 13 mo since purchase. Do you have a test checklist as you follow in the video?
my microwave looks like that one, mine has a very odd issue, when its been working a while and lets' say either loses power in the house or comes unplugged for a hour or so, then comes on, none of the button work, they just beep, cant cook nothing, it has to have constant power for about an hour then the buttons start working again, kinda like a capacitor having to build up power first or something else, i dont know alot about them
I just found you video extremely helpful and I hope that you can help me out. I have a LG LCRT1513ST that is working in all respects except it is not heating. I'm assuming that it is the magnetron. Unfortunately, the problem that I have is that I can not get the case open. The Torx screw openings have a dimple in them that prevents my driver from seating. My question is, "are the case screws proprietary"?
I can't speak to that specific model, but you can find security bit sets on Amazon or elsewhere that contains the proper bit to remove the screws. Here is a link to one such set, I don't know if it has the correct bit though: www.amazon.com/Neiko-10048A-Security-Vanadium-100-Piece/dp/B000O5XDOG/
I'm checking my magnetron on ohms. Red lead on terminal. Black grounded on the case im getting 40.0. I'm lost on electronics..this appears to be bad correct?
Hi Paul, found your video while trying to troubleshoot an issue on my LG LCRT2010ST microwave. Yesterday the display went out. Everything else, including the touchpad, works fine. Just the display is dead. Any ideas on troubleshooting and/or part(s) that need to be replaced? TIA!
Unfortunately, it may be the VFD, (Vacuum Fluorescent Display) which in that case would mean replacing the whole control panel board. Has the display gotten dimmer over time? VFDs slowly go out over time. It could have taken a power spike which could have zapped the VFD. Sorry, I don't have any other ideas.
@@paulstaf thank you for the reply! It started two days ago. It did not get dimmer over time, however, it would go in and out. It would work be working one minute and next time I go to use it, its out. Then again the next time it (the display) would be back. Now it has been out for a while. You mentioned replacing the whole board, would that part be called the "Pcb assembly"? This is the part I'm looking at: lgparts.com/item/9252089/LG/EBR73927306/
Hello paul, i have a problem, i got my microwave LG MS2042D, suddenly off. The condition before is, 220VAC cable is connected to the electrical, and the microwave door is closed but no turn on the microwave, suddenly hear sound like “pop” like something blown. I allready check the fuse from 220vac is normal, check the power through the main relay in panel board is live but the light and panel board is off. Hope you can help many. Thank you
Same problem not heating but ust fixed mine. Door switch spade connector brass lug gone brown looking with tarnish a bit of fine emery and up and running fine
My 2018, LG LCRT2010ST, runs and everything works, but no heat. I checked the transformer and magnetron for shorts and both did not have shorts. How do I check the High heat diode? Could it be the fuse in the small circuit board on the fan housing? What is the white item below the capacitor that says F950mA/L5KV, 2017/10/18. Any other ideas? Hate to throw it out, Is only 2 yrs old...
It is probably one of two things...the power relay, or the magnetron. You can check to see if you have 120V on the PRIMARY side of the transformer...that is the side of the transformer that doesn't go to the magnetron. I usually remove the wires going to the primary side of the transformer and connect a 120V incandescent lamp up to the wires and then run it through a cycle...if the lamp comes on then most likely everything up to that point is good and you have a bad magnetron or fuse on the secondary side of the transformer. I haven't seen a diode go bad yet.
@@paulstaf I guess the 2 leads, the red and back wires attached to one of the transformer leads and the black wire attaches to the other transformer lead, on the side coming from the circuit board, attach those two leads to my voltage meter at 120v setting, or a lamp? Thanks
Apparently the Magnetron on mine is bad also. When I set my meter to resistance and touch both terminals of the Magnetron the meter zeros out. When i hook each terminal and touch other voltmeter lead to the Megetron case, the meter does nothing on each lead.
@@paulstaf There is normally no fuse in the high voltage circuit from the transformer secondary to the magnetron. Your resistance readings on the magnetron connector are misleading, also. The normal reading between the pins is between 1 and 4 ohms. Yes, the reading from the pins to the case, which is circuit ground, should be infinity. If you get any continuity there, it is because there has been arcing inside the connector from one of the pins to the case. If this is the case, replace the connector, not the magnetron. You can get the connectors from Amazon.com for less than $10.
@@paulstaf The high voltage diode is probably the most commonly failed component. The high voltage capacitor can fail also. Be careful to discharge it before touching any of the components. if you suspect that the primary side of the transformer is not getting the 120v, check it with your meter without disconnecting anything, maintaining the normal load on the circuit, instead of a light bulb.
I have a similar microwave & EVEYTHING passes the test. Diode? Check! Transformer? Check! Capacitor? Check! Magnetron filament & insulation? Check! 120v is applied to the transformer primary by the control board, the lights come on, the fan & turntable spin....yet no heat. I have no way to check the 2.5KV secondary AC or the 5KV DC line to the magnetron so I'm stumped. Any suggestions?
I wonder if the power relay is supplying 120V, but not the current needed to run the transformer. I would disconnect the 120V going to the transformer and connect it up to a 100W light bulb or maybe a toaster and see if the load actually powers properly. I wouldn't think your transformer would be bad.
Idk that transformer reading was low like it would blow circuit breaker js it also blew the fuse. U didn't as far as show that it worked n video turn on at least.
The DC resistance of a transformer is quite low. However, for AC voltage the inductance and coupling to the secondary load, increases the impedance substantially. So you are not going to get the kind of current flow that the DC resistance would imply.
Paul, My LG Microwave was making this very loud noise when it was running now there is no sound but it does not heat. Can you tell me what might be wrong. the model is lmh22374st
No, not off the top of my head. First off, If you don't have experience working with mains voltages, reading a schematic, and soldering, then you shouldn't be attempting to repair your oven. You need to use the schematic and a multimeter to trace through the current path of the magnetron. I usually unplug the transformer's input connections (The ones going back towards the control board and NOT the ones going towards the magnetron) and attach a mains rated light bulb to them so I can tell if the voltage is making it to the transformer which in turn would power the magnetron. If the bulb lights then you have a problem after that, if it doesn't, start working back towards the main voltage supply using the schematic. If you are getting mains voltage at the transformer inputs then it could be the magnetron. Consult the schematic....there is probably a fuse on the high voltage side, and if it is burnt, then most likely there is a problem with the magnetron, replacing the fuse will just cause it to blow again.
I just wanted to replace the line fuse, but it looks like you already removed it, so this isn't at all helpful to me. Why they make the fuse cover so freaking hard to open is beyond me, and it would have been nice to watch how you did it.
Usually they have a built in bleed resistor, but to make sure I short them out with a screwdriver. If they have a charge there will be a spark when you short them out, like a large static electricity discharge.
When you checked the transformer, I think you only checked the input primary winding resistance, and the 3v low voltage winding resistance for the magnetron heater element.
The last wire on the secondary side of the transformer is the output for high voltage, and the other end of that winding is bonded/riveted to the core of the transformer, so do the ohms test between hv output wire to transformer core to confirm hv winding is intact.
It's also a good idea to test all windings for shorts to the transformer core.
You can check for shorts in the primary, and low voltage secondary to the core fairly easily, but you'd need to disconnect the /riveted/bonded terminal for the hv winding at the core to test for internal shorts in the winding, or to the core.
Thanks in advance for taking the time to make useful videos and providing guidance! I have an LG microwave lcrt2010st or lsrm2010st installed Dec 2014 (looks very similar to the one in your video. Recently it has been start on its own when door closed, sometimes says door not closed when it is closed, kinda spooky! I was going to replace the 'door switch', but thought I should probably do a bit more investigation prior to ordering parts. My other thought is that the 'touch panel' could be flaking out since it will sometimes start before I have fully specified power level and pressed start. Any input appreciated!
That is a tough one. Sounds like maybe a bad keypad for starters. The door switches could be bad as well. Get a schematic and use it to test the door switches with a multimeter. Not sure how expensive a new keypad would be, but it might be worth changing out as a first step in troubleshooting. Scour the curb on trash day for microwave ovens, you might find parts for yours.
The schematic may be inside the microwave when you take the cover off.
LG SmartInverter model Everything works normal but stopped heating food. Only 13 mo since purchase. Do you have a test checklist as you follow in the video?
Great video thanks!!!
my microwave looks like that one, mine has a very odd issue, when its been working a while and lets' say either loses power in the house or comes unplugged for a hour or so, then comes on, none of the button work, they just beep, cant cook nothing, it has to have constant power for about an hour then the buttons start working again, kinda like a capacitor having to build up power first or something else, i dont know alot about them
I just found you video extremely helpful and I hope that you can help me out. I have a LG LCRT1513ST that is working in all respects except it is not heating. I'm assuming that it is the magnetron. Unfortunately, the problem that I have is that I can not get the case open. The Torx screw openings have a dimple in them that prevents my driver from seating. My question is, "are the case screws proprietary"?
I can't speak to that specific model, but you can find security bit sets on Amazon or elsewhere that contains the proper bit to remove the screws. Here is a link to one such set, I don't know if it has the correct bit though:
www.amazon.com/Neiko-10048A-Security-Vanadium-100-Piece/dp/B000O5XDOG/
I'm checking my magnetron on ohms. Red lead on terminal. Black grounded on the case im getting 40.0. I'm lost on electronics..this appears to be bad correct?
Hi Paul, great video where can I order LG parts?
Hi Paul, found your video while trying to troubleshoot an issue on my LG LCRT2010ST microwave. Yesterday the display went out. Everything else, including the touchpad, works fine. Just the display is dead. Any ideas on troubleshooting and/or part(s) that need to be replaced? TIA!
Unfortunately, it may be the VFD, (Vacuum Fluorescent Display) which in that case would mean replacing the whole control panel board. Has the display gotten dimmer over time? VFDs slowly go out over time. It could have taken a power spike which could have zapped the VFD. Sorry, I don't have any other ideas.
@@paulstaf thank you for the reply! It started two days ago. It did not get dimmer over time, however, it would go in and out. It would work be working one minute and next time I go to use it, its out. Then again the next time it (the display) would be back. Now it has been out for a while. You mentioned replacing the whole board, would that part be called the "Pcb assembly"? This is the part I'm looking at: lgparts.com/item/9252089/LG/EBR73927306/
Hello paul, i have a problem, i got my microwave LG MS2042D, suddenly off. The condition before is, 220VAC cable is connected to the electrical, and the microwave door is closed but no turn on the microwave, suddenly hear sound like “pop” like something blown. I allready check the fuse from 220vac is normal, check the power through the main relay in panel board is live but the light and panel board is off. Hope you can help many. Thank you
If every function operates normally except food not heating is magnetron should I bother with repai
Same problem not heating but ust fixed mine. Door switch spade connector brass lug gone brown looking with tarnish a bit of fine emery and up and running fine
My 2018, LG LCRT2010ST, runs and everything works, but no heat. I checked the transformer and magnetron for shorts and both did not have shorts. How do I check the High heat diode? Could it be the fuse in the small circuit board on the fan housing? What is the white item below the capacitor that says F950mA/L5KV, 2017/10/18. Any other ideas? Hate to throw it out, Is only 2 yrs old...
It is probably one of two things...the power relay, or the magnetron. You can check to see if you have 120V on the PRIMARY side of the transformer...that is the side of the transformer that doesn't go to the magnetron. I usually remove the wires going to the primary side of the transformer and connect a 120V incandescent lamp up to the wires and then run it through a cycle...if the lamp comes on then most likely everything up to that point is good and you have a bad magnetron or fuse on the secondary side of the transformer. I haven't seen a diode go bad yet.
@@paulstaf I guess the 2 leads, the red and back wires attached to one of the transformer leads and the black wire attaches to the other transformer lead, on the side coming from the circuit board, attach those two leads to my voltage meter at 120v setting, or a lamp? Thanks
Apparently the Magnetron on mine is bad also. When I set my meter to resistance and touch both terminals of the Magnetron the meter zeros out. When i hook each terminal and touch other voltmeter lead to the Megetron case, the meter does nothing on each lead.
@@paulstaf There is normally no fuse in the high voltage circuit from the transformer secondary to the magnetron. Your resistance readings on the magnetron connector are misleading, also. The normal reading between the pins is between 1 and 4 ohms. Yes, the reading from the pins to the case, which is circuit ground, should be infinity. If you get any continuity there, it is because there has been arcing inside the connector from one of the pins to the case. If this is the case, replace the connector, not the magnetron. You can get the connectors from Amazon.com for less than $10.
@@paulstaf The high voltage diode is probably the most commonly failed component. The high voltage capacitor can fail also. Be careful to discharge it before touching any of the components. if you suspect that the primary side of the transformer is not getting the 120v, check it with your meter without disconnecting anything, maintaining the normal load on the circuit, instead of a light bulb.
I have a similar microwave & EVEYTHING passes the test. Diode? Check! Transformer? Check! Capacitor? Check! Magnetron filament & insulation? Check! 120v is applied to the transformer primary by the control board, the lights come on, the fan & turntable spin....yet no heat. I have no way to check the 2.5KV secondary AC or the 5KV DC line to the magnetron so I'm stumped. Any suggestions?
I wonder if the power relay is supplying 120V, but not the current needed to run the transformer. I would disconnect the 120V going to the transformer and connect it up to a 100W light bulb or maybe a toaster and see if the load actually powers properly. I wouldn't think your transformer would be bad.
Idk that transformer reading was low like it would blow circuit breaker js it also blew the fuse. U didn't as far as show that it worked n video turn on at least.
The DC resistance of a transformer is quite low. However, for AC voltage the inductance and coupling to the secondary load, increases the impedance substantially. So you are not going to get the kind of current flow that the DC resistance would imply.
What the meaning of this codes in
LG micro wave..
AC 1 and AC 5.. pl reply sir... Thank you..
Need parts for door switch
Paul, My LG Microwave was making this very loud noise when it was running now there is no sound but it does not heat. Can you tell me what might be wrong. the model is lmh22374st
No, not off the top of my head. First off, If you don't have experience working with mains voltages, reading a schematic, and soldering, then you shouldn't be attempting to repair your oven. You need to use the schematic and a multimeter to trace through the current path of the magnetron. I usually unplug the transformer's input connections (The ones going back towards the control board and NOT the ones going towards the magnetron) and attach a mains rated light bulb to them so I can tell if the voltage is making it to the transformer which in turn would power the magnetron. If the bulb lights then you have a problem after that, if it doesn't, start working back towards the main voltage supply using the schematic. If you are getting mains voltage at the transformer inputs then it could be the magnetron. Consult the schematic....there is probably a fuse on the high voltage side, and if it is burnt, then most likely there is a problem with the magnetron, replacing the fuse will just cause it to blow again.
Hi. I have a lg inverter microwave. It keep saying door and stops after 3 seconds of operation. What could be the problem.
probably one of micro switches for the door is miss behaving
secondary winding should be 65-120 ohm. and primary winding 0.3-0.5 ohm. You tested both winding at 0.2 ohm. Is that right???
I don't know what it should be, in the video the primary was .9 and the secondary was .2.
The microwave has been working for a couple years almost since the repair.
I just wanted to replace the line fuse, but it looks like you already removed it, so this isn't at all helpful to me. Why they make the fuse cover so freaking hard to open is beyond me, and it would have been nice to watch how you did it.
How did you discharge the capacitor on this one ??
Usually they have a built in bleed resistor, but to make sure I short them out with a screwdriver. If they have a charge there will be a spark when you short them out, like a large static electricity discharge.
CAN I REPLACE A MAGNETRON OF A DIFFERENT BRAND
I don't know, never tried it. I usually stick to OEM, or suitable subs.
Where’d you get the parts ?
Amazon, but of course!
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