Microwave got hot and now not powering up - Page 1
Forum section: electronics / repair

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 02:35:02 am
content: Hi folks,My wife was cooking some potatoes for a good 10 minutes when the microwave just stopped working. Now it won't power up.I noticed the side of the cabinet with all the electronics was very hot. I opened it up and the large transformer on the bottom of the cabinet is burning hot. The Galanz magnetron is warm, but not as hot as the transformer, and the large cap attached to the transformer is fairly cool. All of the components, transformer and such on the micro panel with display and buttons is cool.I am wondering where to start. First, I don't want to dry myself with that large cap. How do I safely discharge it? Can I use a multimeter and how? Should the transformer get that hot?I notice there is a plastic encasing on one of the wires going from the transformer to the cap... what is in there? does anyone know if there are thermal cutoffs or resettable fuses that are responsible? I will post a few photos.

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 02:50:32 am
content: Here are some pictures. The large transformer is by far the hottest thing in there. Is there a thermal fuse buried in the windings? The Magnetron above it also is hot but maybe because it was directly above or connected thermally? The large cap is cool. Notice that white casing around the red wire that is being supported by a white stem... what is that? I doubt it is the fuse on the power input but couldn't hurt to check continuity. Any ideas would be appreciated.

author: Riotpack
author_rank: Regular Contributor
timestamp: December 12, 2014, 02:51:36 am
content: Did you give it a good hour to cool down? It might just be the reset able thermal fuse. Also is the unit totally dead?

author: Riotpack
author_rank: Regular Contributor
timestamp: December 12, 2014, 02:56:59 am
content: I cannot see any pictures posted.

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 02:59:56 am
content: Sorry I forgot to add the photos... here they are.It died just 30 minutes ago. I unplugged it and waiting to figure out what to do next. I was thinking to plug it back in after it cools down. Yes the display is completely dead. No time showing, no beeps, no lamp light when door open.

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 03:07:53 am
content: I touched the transformer block and it is still quite hot, almost 30 minutes later. Everything else has cooled. It must have a ton of thermal mass. Burns my fingers still.I see a couple of devices on the top of the unit. Are these sensors? See photo...

author: Riotpack
author_rank: Regular Contributor
timestamp: December 12, 2014, 03:08:45 am
content: Test the two thermal fuses after isolating the supply - there's a good chance it is one of them, it may even be working again by now.If the HV fuse is blown the microwave would still power on but would not cook.I would leave the HV side alone for the moment, it should not affect the main power. It also runs at a couple of kV and has a capacitor (which should have a bleed resistor) so be careful around there.

author: Riotpack
author_rank: Regular Contributor
timestamp: December 12, 2014, 03:15:33 am
content: Heres a basic guide to repairing Panasonic Inverter types if anyone reading is interested.https://onedrive.live.com/view.aspx?resid=1AB6590A9FB4749D!3186&ithint=file%2cpdf&app=WordPdf&authkey=!AC-P6Lmhg7gvhbA

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 03:52:47 am
content: Thanks again for the advice! You are right!!!It was the thermal fuse. Thankfully it was a false alarm.... turns out one of the thermal protection fuses (probably the one on over the Magnetron housing) tripped and shut it down. I waited until everything cooled down again and plugged it in to hear that familiar "beep" and saw my LED panel blinking on. Good to know it was nothing major.As much as I'd love the fun of troubleshooting and repairing the microwave right now, we kind of depend on it heavily to heat up food for the whole family including baby and I didn't feel like trekking out in the middle of the night (during a snow blizzard) to buy a microwave just so we can feed our kids in the morning. Thanks again.

author: SL4P
author_rank: Super Contributor
timestamp: December 12, 2014, 04:14:02 am
content: Quote from: edy on December 12, 2014, 03:07:53 amThatsays a lot in itself.Throw it out and spend $80 at the local discount warehouse.If not your life - save your family.

author: Psi
author_rank: Super Contributor
timestamp: December 12, 2014, 04:42:42 am
content: Yeah, sounds like its a cheap POS built to within an inch of its life.I agree with SL4P, throw it away.Don't combine crap quality/design with really high voltages. It's just not worth it.Be thankful they actually fitted a thermal fuse at all.If it had no thermal fuse, and had a bad earthing connection, the overheating could have broken down the transformer insulation and perhaps shorted 2kV to the metal case

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 06:12:10 am
content: Advice well taken. I just don't know if I buy another one whether it is built to any better quality or most likely it will be another P.O.S. I've attached a photo of the model. Danby is some cheap Wal-mart brand I believe. Here it is ($80):http://www.walmart.ca/en/ip/danby-11-cu-ft-capacity-microwave/6000043118699This is the first time I've had it heat enough to turn off. My wife had it cooking maybe 10 minutes, not sure what setting she used. And why is it happening now (or was it always this bad we just never used the micro that long). What is the problem with the transformer and should I look into an inverter type mico instead? Is it even worth replacing that transformer (if indeed it is overheating, and how do I know for sure)? What would cause it to heat more than previously now?

author: SL4P
author_rank: Super Contributor
timestamp: December 12, 2014, 06:17:30 am
content: There is alotof rebadging going on in both domestic and professional equipment.Until about 8 years ago, I thought Cisco made their own stuff - but learned they often buy-in and rebadge many items of equipment. (think video CMS / distribution products).For microwaves - start with Panasonic, LG or other OEM manufacturers.They will be a little more exxy, but have a traceable warranty and safety history.

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 06:20:46 am
content: Check this out... I found a whole bunch of info on Danby and overheating.First a YouTube video of a guy with the same model as I have testing temperature:And then this post on another website:http://www.fixya.com/support/t15707922-microwave_stops_working_when_heatingAnd I quote...Question about Danby Designer Series DMW111KPSSDD:QuoteAnswer:Quote

author: miguelvp
author_rank: Super Contributor
timestamp: December 12, 2014, 06:39:53 am
content: Quote from: edy on December 12, 2014, 06:12:10 amThat's your problem right there, shop at Sears instead, Walmart is just like an Ebay store front.You are better off buying from alibaba because you'll get the same walmart quality at a lower price. Walmart is known to pressure domestic manufacturers to bring their prices down to Chinese imports realm, so something has to give and usually is layoffs and poorer quality, but the lure of high volume sales attract local manufacturers to that trap.Then again Sears and the like are bringing their prices down as well so the epidemic is spreading.

author: coppice
author_rank: Super Contributor
timestamp: December 12, 2014, 06:43:08 am
content: The oven was made in FoShan, which is the home of Galanz. It has a Galanz magnetron. It seems likely the whole oven was made by Galanz. As they are the world's biggest maker of microwave ovens, its pretty likely many of the alternative ovens in your local shops were also made by Galanz. You might buy from big international brands, and still find you have a rebadged Galanz oven. Its hard to know what you are getting they days, until you ..... don't turn it on. Take it apart. :-)How many potatoes were in your oven when it overheated? Its quite common for empty, or nearly empty, ovens to overheat and shutdown after a while. Especially smaller ones, without a good cooling airflow.

author: SL4P
author_rank: Super Contributor
timestamp: December 12, 2014, 10:35:09 am
content: Not bad-mouthing any particular manufacturer, but I wonder if emission tests would reveal nasty things leaking out of cheap/poorly assembled microwaves ?What's needed to do this objectively?

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 01:59:59 pm
content: After some further questioning, my wife divulged that she had been cooking some 5 medium sized sweet potatoes (aka yams), which as you know are quite firm initially and probably don't have a huge amount of water, nor radio penetrability. So I think the volume of potato and time of cooking (around 10 minutes) overtaxed the capabilities of this 1.1cu ft P.O.S. from FoShan. But to play devils advocateI think most microwaves today would choke on this as well, and there is no way to know what is inside unless I bring a screwdriver to the store.Likely almost every microwave, electric tea kettle, toaster, mixer and other kitchen or small home appliance is made in a place like Factory City China and just designed and branded for what we consider non-Chinese brands.http://youtu.be/xMm-YMO5H7oAnyways if it starts happening on more "easy" cooking situations and less time, I think it's safe to say the device will have to be tossed. Which begs the question, how do you know if a Magnetron starts to go bad? Is there any test that is easy to conduct? What about the transformer heating? Is this a symptom of another faulty component or the transformer itself? And even if we have a definite diagnosis of the problem, since a new one is $80 is it economically feasible to even bother fixing up a piece of crap like this, or buy a new one every 3-5 years?

author: coppice
author_rank: Super Contributor
timestamp: December 12, 2014, 03:04:24 pm
content: Quote from: edy on December 12, 2014, 01:59:59 pmThat place is tiny. Only 17k workers? The Hon Hai plant in Dong Guan, where Apple gets a lot of its stuff made, slaughters 8000 pigs a day just to feed the workforce in the works canteens.

author: Macbeth
author_rank: Super Contributor
timestamp: December 12, 2014, 03:32:41 pm
content: Quote from: edy on December 12, 2014, 03:52:47 amThat makes me kind of sad. I've got a good microwave with grill and fan oven etc. but rarely use it. It's good for reheating stuff, but I can't imagine relying on a fecking microwave for cooking the family dinner.(It just so happens I am off to pop my roast beef in my gas oven for a nice long slow 4 hour roasting. Par boiled spuds ready to be bashed in oil, salted, and blast roasted at gas mark 9, roast parsnips, yorkshire puddings, fresh gravy from the beef juices, horseradish sauce... yum!)The joint of beef and the amount of spuds, parsnips, yorkies I *could* cook would be enough for 3 families. But it's just MINE! ALL MINE!!! (and my dogs). It also costs feck all compared to microwave TV dinner meals.

author: SeanB
author_rank: Super Contributor
timestamp: December 12, 2014, 03:59:32 pm
content: I would check the fan is turning freely, and the vents on the back and side are clear so that air flows in from the back and out the side. as well do not place it right against the back of the cabinet, and make sure there is room for the hot air to exhaust if it is in a cabinet. Running the oven without air flow will overheat it fast as you have found out.

author: edy
author_rank: Super Contributor
timestamp: December 12, 2014, 04:06:20 pm
content: Macbeth, you are lucky to have that "luxury ". Our life is quite hectic with 3 kids and 6- day a week jobs into late nights sometimes... so sadly cooking fresh has been sacrificed and I'm sure I am paying with health consequences. Instead, stuff is prepared on weekends and we nuke them the whole week (at least my meals) until there is nothing left of it. The kids eat better but still tend to get reheats, usually microwaved.But this has really opened my eyes on how reliant we are on this device. I am going to ask my wife to figure a way out of this lifestyle as its going to kill us both.

author: WarSim
author_rank: Frequent Contributor
timestamp: December 12, 2014, 04:23:43 pm
content: I get a kick out of these assumptions. Work had 12 microwaves with "dead magnetrons" stacked in a corner to be recycled. Every single one was fixed by replacing one of the safety switches. After safety testing I ended up with 11 fully functional microwaves for $189 each.I sunset you check the safety switches before you assume something more dire. There should be at least 7, depending on your country.

author: Macbeth
author_rank: Super Contributor
timestamp: December 12, 2014, 04:34:30 pm
content: edy, I get the impression you and your wife make a decent batch of food on the weekend, then freeze it and reheat for dinner using the mikey. Nothing wrong with that, but you can also reheat frozen (cooked) food in the gas oven, or stove top too.The pre-packaged microwave TV dinner shite - it's packed with loads of salt to pretend to give it some protein umami flavour, but to counteract it, is packed with sugar because the salt is just too much. The "meat" is nearly always chicken even if the pack states it's beef or lamb. Maybe 5% of them, the rest is turbo-blasted polyphosphate degenerated bits of chicken carcass.I know it's fecking hard at times to feed a family, which is possibly why I don't have one of my own. I remember living in single bedsit hotel rooms with nothing but a kettle as a child, and having to live on instant mashed potato, boiled eggs, and frankfurters - all done in a kettle. My mum was so proud of what she could rustle up.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: December 22, 2014, 03:08:20 am
content: Quote from: SL4P on December 12, 2014, 10:35:09 amThey already do.edit: to anyone wondering, this is a wifi spectrum analyzer, moments after turning on a nearby (3-5 meters) microwave. It just trashes the entire spectrum.

author: cjacob
author_rank: Newbie
timestamp: September 10, 2017, 09:21:11 am
content: There is a discussion going on at iFixit, please checkhttps://www.ifixit.com/Answers/View/55644/My+microwave+is+not+heating%2C+but+the+timer+is+working.as well.

author: hermit
author_rank: Frequent Contributor
timestamp: September 10, 2017, 02:27:26 pm
content: Quote from: edy on December 12, 2014, 02:35:02 amDiode. You need about 9 volts to read it. DMM generally won't work unless you add some voltage. Analog might do it.

author: oldway
author_rank: Super Contributor
timestamp: September 10, 2017, 05:03:25 pm
content: How to repair a microwave oven safely ?(only electrical safety)

author: Gyro
author_rank: Super Contributor
timestamp: September 10, 2017, 06:00:01 pm
content: Quote from: hermit on September 10, 2017, 02:27:26 pmNOTE: This is a repair thread from back in 2014.

author: hermit
author_rank: Frequent Contributor
timestamp: September 11, 2017, 02:58:27 am
content: Quote from: Gyro on September 10, 2017, 06:00:01 pmHmmm... I didn't note the date but a first/one time poster who registered today bumped the thread to link to another site? hmmm.....

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: September 12, 2017, 07:39:27 am
content: If the transformer is overheating, likely reason is that the rectifier diode is s/c. These are a special type designed for the voltage involved. Of course the transformer insulation might be damaged if the overheating is severe.The rectifier, along with the capacitor wired in series, is a voltage doubler. If you're wondering how you achieve a voltage doubler with only one diode, well actuallly you don't. The magnetron acts as the second diode.Usual warning about some really dangerous voltages in these thngs. Don't forget to dump any residual charge on the cap before handling, with a well-insulated tool.

author: hermit
author_rank: Frequent Contributor
timestamp: September 12, 2017, 02:02:44 pm
content: Quote from: IanMacdonald on September 12, 2017, 07:39:27 amMost modern ones have internal bleed capacitors but don't bet your life on them.