Replacing A Magnetron

[voipio]

Is the diode definitely open circuit? They have a forward voltage drop of ~8V so may be too high for an average multimeter ... beat me to it!!

Ohh. You have three hands!!!

 

[Ian X]

create quite impressive arcing, especially if it's aluminium foil.

I used to visit Ilford Photochemical as a contractor, at lunch there was a canteen regular who melted portion size butter wraps on a plate in one of the microwaves, 2.7kW input. He would stand close to look through the window in order to monitor the "doneness" and his face would be lit up by the activity inside the cooking chamber. It was in Cheshire, "strong in arm...".

 

[Onoff]

Hmmm...

First off the microwave made a noise and stopped heating. The screen etc worked fine.

The magnetron measures under 1 ohm, circa 0.3.

Did an IR test between each terminal on the magnetron to the case, infinity.

The cap measures 1uF.

The diode appears OK testing it with a 9V battery in series.

The 750mA, 5KV fuse had popped. I replaced it and swapped the cap out as the 1uF looked a bit swollen perhaps even though it tested OK. I only had a 1.14uF cap so put that in.

Turning on and it seemed to start but then popped an 8A fuse. This one I'm pointing to. Now the screen is dead.

https://flic.kr/p/2qz8TNT

 

[Kayos]

I'd say it's heading skipwards

 

[Ian X]

In the words of the locals, c'est mort.

 

[Onoff]

Well it's working again. Only took a year...

 

[Smallfry]

Well it's working again. Only took a year...

I am surprised it works at all, after cutting a lump out of the casing.

 

[Onoff]

I am surprised it works at all, after cutting a lump out of the casing.

Only tried the microwave. Not the oven or grill yet.

 

[rtcosic]

Well it's working again. Only took a year...

Spontaneous Parthenogenesis of the required part? Or did you intervene?

 

[Onoff]

Spontaneous Parthenogenesis of the required part? Or did you intervene?

Actually gave up originally but SWMBO kept on. Took to a place someone recommended up the pub.

Bloke confirmed it was just the original 1uF capacitor was duff as I suspected. Weird as I'd replaced it with a new 1.14uF and it still popped the internal fuse.

I'd have thought that with the tolerance on 1.14uF it would have been fine.

 

[Kerelise]

About 20 years ago I was told that a cafe owner in Swaffham found opening and closing the door to his microwave oven too hasslesome and time consuming, so to shave off some prep time, he just removed the door to the microwave oven and jammed some folded cardboard into lock mechanism….

 

[Farside]

Most of you who have gone out and bought a new microwave after it has gone bang have done so unnecessarily.
In most cases it’s not the magnetron which has gone wrong it’s the little biscuit coloured cover which attaches to the wall of the microwave which covers the magnatron.
I don’t claim to know the science behind it but that little cover needs to be in good condition, if your microwave goes bang, remove this cover and replace it, you’ll notice a burn mark on it as though something very hot has been arcing on it.
These are readily available on eBay cut to size, or you can buy a generic one and cut it down to size yourself.
I’ve a spare one in the cupboard for when it happens again.

View attachment 474105

Yep, did that on an old one about a year ago, it's been fine since. I now have another five spare.

 

[Guineafowl]

About 20 years ago I was told that a cafe owner in Swaffham found opening and closing the door to his microwave oven too hasslesome and time consuming, so to shave off some prep time, he just removed the door to the microwave oven and jammed some folded cardboard into lock mechanism….

Interesting point by an electrical engineer on YT (Electroboom), that EM radiation longer than UV “only” causes damage by local heating, unlike the shorter waves that cause DNA damage. Other sources suggest indirect DNA damage by oxygen radicals, so it might be a bit more complicated.

 

[Dapph2]

About 20 years ago I was told that a cafe owner in Swaffham found opening and closing the door to his microwave oven too hasslesome and time consuming, so to shave off some prep time, he just removed the door to the microwave oven and jammed some folded cardboard into lock mechanism….

Arrrrrr E B Norfolk 'N' good , replete with 12 fingers , four thumbs & eats raw carrots by the bucket full.

 

[Cobbler]

Interesting point by an electrical engineer on YT (Electroboom), that EM radiation longer than UV “only” causes damage by local heating, unlike the shorter waves that cause DNA damage. Other sources suggest indirect DNA damage by oxygen radicals, so it might be a bit more complicated.