How to a Fix a Microwave Oven
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- Опубліковано 5 тра 2016
- Here I fix a microwave oven. Never tried it before, but ended up with a successful fix. So anyone with some common sense and a 'go do it' attitude can do the same.
Just be careful to avoid electric shock. Disconnect from the main supply. Preferably leave a few minutes for the internal high voltage capacitor to discharge, and also short across the capacitor as well to make sure (see video).
Only reconnect the supply once all of the covers are back in place.
A warning on the materials used in the magnetron: If your magnetron has a pink ring around it, then it contains beryllium oxide, which is extremely toxic if crushed, SO DON’T CRUSH IT and then breath in the dust, otherwise it is inert. See electronics.stackexchange.com....
The main microwave generation circuit is very simple, consisting of a transformer, fuse, diode, capacitor and a magnetron valve. Some other models like inverter models may be more complicated.
Take a note, preferably a picture, of how everything is assembled and wired up, so you can reassemble it the same.
In this model of microwave (a DeLonghi AC925), both the magnetron and the capacitor needed changing. The total part cost was only about £25, including post.
If you need new parts you could try here for example:
Capacitor: UK: amzn.to/28SsWYB In USA: amzn.to/28ZIFTb
Magnetron: UK: amzn.to/28Su4LJ In USA: amzn.to/28PcKlk
HV fuse: UK: amzn.to/28PdDKY In USA: amzn.to/28TdTw4
eBay is also always a good source of parts, for instance,
magnetrons on eBay uk: ebay.us/YsQR2Q
And magnetrons on eBay USA: ebay.us/DrPrVC
HV capacitor on eBay uk: ebay.us/UUUKah
HV capacitor on eBay USA: ebay.us/zoeoYt
I show how to test the diode and capacitor to find out whether they are good or blown.
Hopefully you can save some money and fix your own. Good luck.
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Many thanks to you for posting this video. Using your guidance, I have successfully replaced the faulty magnetron in my two-year old Delonghi and it's now working perfectly again. Part cost £22 delivered (via eBay) and about 30 minutes taken to complete the job. 🤗
Great! Well done!
Impressive video! Young adults these days don't know how to fix shit.. it's sad.
Cheers. Yes that seems true, my mission is to help people learn how to fix stuff.
Спасибо, очень полезное видео, мне удалось починить свою микроволновку
Thanks. Congratulations.
Great video.
Cheers.
Nice informative video, however just a couple of things to add. Firstly never use a phase tester screwdriver, most especially on a HV source it could be fatal as the end cap can delivery a shock!
Also the use of a capacitance meter to check the capacitor will give a correct uf value that can be compared to the accepted value. (Within the allowed tolerance).
Also, the HV diode junction uses more current than a multimeter can deliver on diode test mode, so as you later showed you need to feed a DC voltage through it and then measure this with a multimeter, it should have dropped by a few volts if correct, reverse the connections and ensure that it blocks the reverse voltage completely. A diode allowing the full test voltage to pass in either or both directions is duff and needs to be replaced.
Thanks. Just one correction: The HV diode is a higher voltage drop rather than higher current than the multimeter can produce. A multimeter produces around 2 volts to test normal diodes that drop 0.7v, and the HV diode is probably several diodes in series internally so has a drop of several volts and the multimeter just sees it as open circuit.
very helpful, but ahhh the screeching sound!!!
Great video thx m8
Cheers
Good video but please use a piece of card board (or other material) to put the magnetron on to prevent damage and that terrible screeching sound. Thanks.
The white ceramic part of the magnetron is beryllium and one should be very careful with it. If it is broken or crushed and some of the dust is inhaled it can cause serious illness or even death.
Thanks for your advice. I will put a warning into the comments.
Fabulously informative video, well done. I would recommend that you make yourself a simply discharge cable with a resistor to discharge the capacitor. If you simply used a screwdriver to short the terminals, you very likely caused the damage to the capacitor. But a very good video nonetheless.
Thanks. It seemed to discharge on its own after a few minutes. The shorting out is just to be sure.
I like for video.
Thanks. P.S. now on facebook as well facebook.com/comeinhandynow
my microwave died but didn't make a popping noise and there was no acrid smell. i replaced the fuse and now the microwave will power up and display the clock and count down when entering a cook time but there is no cooking, the fan does not come on and the table does not rotate. the light does come on. which do you think it is, the capacitor or the magnetron? would the table and fan still work if the capacitor was good but the magnetron failed? excellent how video- thanks
I would guess another internal fuse has also gone. The thing to look for is what is the common component in the supply to the fan and turntable and magnetron circuit. Also you need to test the capacitor and diode, if it has that type of circuit, to try and work out why the fuse blew in the first place. And lastly be careful with those high voltages, don't attempt it if you are not aware of the hazards and what aware of the precautions to take.
I have a similar problem. Halfway through some food reheating, the internal light went out, the turntable stopped turning, and the microwaves had also stopped. But the count down timer kept on going all the way down to zero.
So I can start the timer, and it ticks away as usual, but that is as good as it gets. Nothing else works.
The only fuse I can find is the main AC line fuse, and of course it is still OK.
All three micro switches that are activated by the closed oven door, all seem to be OK.
So I am stuck on this one.
UPDATE: I took a second look at the micro switches. One was intermittent. The poor electrical connection heated up the switch which is what lead to the mid food reheating fail to occur, all due to a sudden open circuit occurring because of the heat. It turned out that my slamming the door closed weeks before hand had damaged the micro switch by displacing an internal component. Fortunately the switch was easy to open, and so a quick repair was dead easy to do. I love it when a repair costs nothing at all.
Very good video.I have a Russell Hobbs flatbed.Its only over a year old.There are only 4 buttons on this model - Microwave,Defrost,Stop/Cancel and Start.Micowave and Defrost buttons work as they should.They add time in increments if 30 seconds.Pressing start does nothing and also pressing stop/cancel,which should zero the time inputed,does nothing.I have tested the door micro switches and look ok.
Any ideas my friend?
Either a lost/ broken connection to the circuit holding the push button switches or a main controller fault. All you can really do is check for anything obviously out of place. Possibly check the resistance on the start or cancel button wires at the main pcb to see if they to to zero when pressed.
I did strip all the PCBs and nothing looks amiss.Maybe a slight discolouring around resistors.I think it is a PCB problem.A relay perhaps.Thanks for very prompt reply.
@@alanweir3567 A discoloured resistor is often a good clue to an overheated and possibly failed resistor, so worth checking it’s resistance and compare to the value indicated by it’s colour bands if they are at all readable. If it has failed it will be an open circuit.
Resistors seem ok.Measured with multimeter.Maybe a relay problem.Thanks again.
it is a voltage doubler - magnetron gets around 5kv volts of raw DC
Not what I would call a voltage doubler. If one side of the output from the transformer is going from +2800v to -2800v with respect to the other side, then the peak to peak voltage is 5600v. The shown circuit just shifts that to a dc output of -5600v or 0v(when off). The p-p difference is still 5600v so no doubling. More like a rectification and dc shift. It’s a cheap equivalent to full wave rectification which would do the same thing and also produce 5600v.
you are correct it is 5600V peak . The circuit doubles as on one half cycle the diode conducts , causing the capacitor to charge up to ~2800V . , on the other half cycle the capacitor is in series so the 2800V in the cap is added to the 2800V from the transformer and is raw DC .
the transformer is not a 2800 - 0 - 2800 centre tapped transformer , so emits 2800 VAC. hence the diode and cap charge pump is a voltage doubler.
I just fixed my sanyo microwave , hence i visited your video :) , cap, diode and magnetron was fine, the fuse had blown inside though so i replaced it.
This was probably due to a high standing wave reflection from a sachet meal and the fuses ages. Eventually it will fail as it is spring loaded to fail and even moderate heating will fatigue it over time.
I wonder how many microwaves meet the dustbin due to this spring loaded fuse failing? I am guessing this is a design feature for lifetime limitation.
Well done for fixing yours. Calling it a doubler or not is all down to how you look at it. The maximum voltage wrt to gnd is doubled by the cap diode, but my viewpoint is that it’s really just doing a dc shift as if you put a scope (high voltage!) on point “+”, the transformer output, it is an ac output of +/-2800v, this is 5600v p-p. That 5600v ac signal is dc shifted by -2800v by the cap diode to the same amplitude 5600v p-p ac signal but the output now gives from 0 to 5600v instead of from +2600v to -2600v.
much that i dislike to differ. the only place you would get +/-2800V is if you had a centre tapped 2800 - 0 - 2800 v transformer. With a single 2800v secondary winding (ignoring the magnetron heater coil) the voltage if measured across the outputs off load will be around 2800V AC peak to peak.
If of course the magnetron is a 2800V device then the transformer output would be ~1400v .
The ingenious simplicity of the circuit in using a diode and capacitor to both rectify and voltage double cannot be denied though.
My microwave is exactly the same inside and i am guessing there are very few companies making the guts for them. the only differentiator is the box and human interface malarky.
cheers
If one side of the secondary transformer output is connected to ground, as in the picture, then the other side of the output, which is a.c., will alternate from +2800v to -2800v as a sine wave over the time period of its cycle. Hence a peak to peak difference over the time period of the whole ac cycle of 5600v. This is what p-p is. It does not mean a voltage difference at a single moment in time of 5600v.
most common fault is not magnetron, it is high voltage fuse
+bargainszone Thanks for your input. There is usually a reason for a fuse blowing, and although the magnetron needed changing in this microwave (as it had a hole burnt in it, that shouldn't have been there), I think what is maybe more common is the high voltage capacitor, which had shorted in my microwave. Capacitor ageing is a very common problem on all sorts of electronics, and the higher the voltage the more stress they are under. Maybe the fuse blowing is just symptomatic of the capacitor on its way out by starting to leak current.
comeinhandynow hi . i have here a whirlpool and this when i pish the start for heat this blown the fuse. onmy in that moment. you think maybd is the diode? i see in this model the diode is very cmose to the capacitor..
Lol is there anything that hasn't failed on your microwave??
Lol. The turntable still went round!
60 bucks for a new micro wave why go though all this crap?
No it was closer to $400 new. It was a top of the line multi function one. So it was well worth it. And it saves throwing away all that crap. Save the planet, fix stuff! ;)