Replacing A Magnetron

[Onoff]

SWMBO went out leaving the microwave on. I heard a single loud buzz like if metal had been left in there (it hadn't).

Back she came to continue cooking and soon declared it to not be working. A massive old Sanyo combi. The conventional oven and grill still work.

So...spare microwave dragged out from lad's uni days, dinner done and strip it on the breakfast bar. Needs a hoover. How do crumbs get along the top edge?

This connector on the magnetron appears a bit charred:

Assuming it's that then the only one I can find is £40 secondhand:

 

[jimbo84]

The built in combi microwave packed up 2 weeks after moving into the new (to us) house. I suspected the magnetron, a new replacement was something like £70 but the microwave was 10 years old, I wasn't sure whether or not it was the magnetron and didn't want to gamble without any definitive way of testing it. A direct AEG replacement microwave was a bit spendy so ended up with an indesit one at half the cost with a 2 year guarantee on it. Some things really aren't worth fixing.

For £40 it may be worth a gamble but may also just be throwing good money after bad depending how old it is.

 

[500e]

Just pulled the Zanusi to bits new control board £ 116. and back light board £ 21. 3 dam LED on a 1p bit of board, built in model and strange size.
New unit to fit £450

 

[Parm]

I’ve just bought a new microwave, looked for ages to match functions n size with the previous model that I’d had for over 18 years then realised that I don’t need to play top trumps as I never any of the functions, just need it to heat stuff up occasionally, so bought another Samsung, this time a basic one but as big as they come.

 

[Ali]

I’ve just bought a new microwave, looked for ages to match functions n size with the previous model that I’d had for over 18 years then realised that I don’t need to play top trumps as I never any of the functions, just need it to heat stuff up occasionally, so bought another Samsung, this time a basic one but as big as they come.

Ours broke and I just went out and bought one the same day. Was instructed by wife to return it to the supplier immediately, and she then spent 6 weeks browsing the various models, comparing features, pricing, colour etc. etc. It would be nice if she decided on exactly the same model - no, but she likes it. I just don't have time for comparing all these useless features*

*unless it's a new power tool or guitar.

 

[Tom O]

I had the electrical panel replaced for more circuit breakers in the garage but when main power turned back on it killed the microwave. Timer & clock work though.

 

[minimutly]

Panasonic, wedding present , 38 yrs ago.... It failed some 20 yrs ago, I announced confidently, it's had it, get another. "Best check the fuse" she said, well it had blown... Replaced, still working

 

[RichardM]

Replaced our old one, when the playe broke, luckily it wasn't me! It was still working but not as quick as it used to heat stuff.
Only criteria for is is that the dogs bowl needs to fit to warm his food up slightly.
I don't think I would bother to repair one, but the micro switches came on handy to replace the ones in the central heating valve.

 

[Smallfry]

I’ve just bought a new microwave, looked for ages to match functions n size with the previous model that I’d had for over 18 years then realised that I don’t need to play top trumps as I never any of the functions, just need it to heat stuff up occasionally, so bought another Samsung, this time a basic one but as big as they come.

Much the same as buying a washing machine really, most features are never used, so whats the point, except to impress your friends.

Our Panasonic microwave must be thirty years old, and gets used every day. It has a clockwork ? rotary timer dial, and min, med, and max settings.
Ex boss and other friends have bought expensive programmable touch button things, but none of them have lasted long.

SWMBO does the cooking, and says that if you want stuff browned or roasted, buy a proper oven. Will having a proper oven be another thing we are not allowed to have, due to climate change targets ?

Regarding changing the magnetron, the few microwaves I have taken apart, always seem to have burnt connectors at the magnetron, which suggests overload and high resistance to me.

 

[AVI_8]

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.

 

[Seadog]

It's a piece of mica that prevents food entering the waveguide.
I had an interesting little flare-up in mine a few weeks back.
I must clean it sometime

 

[Ton-up]

As you lot are talking about microwaves, can anyone explain this what happened this week?
For as long as I can remember, at least once a week my wife has partly cooked baked potatoes in the microwave by placing them on a piece of kitchen roll and cooking for 6 minutes, then they go in the conventional oven for a while.
Anyway, this week she walks back in the kitchen and the kitchen roll is on fire inside the microwave. Why did it catch fire this time?

 

[voipio]

Putting any sort of tissue into a microwave is not recommended. Was the kitchen roll damp and possibly curled over at some point, especially from the steam coming from a jacket potato that's been in there for 6 minutes? The wavelength of the RF emissions of typical microwave ovens operating at 2.45GHz is 12.2cm. It's quite easy for adjacent bits of conducting material to reach quite high RF potentials, especially if there are half-wavelengths involved, and sufficient to create quite impressive arcing, especially if it's aluminium foil. Not only that, but the RF currents, induced in any conducting materials, can be quite high. With tissue paper products, even a small amount of moisture in the tissue could be sufficient for the heating effect to raise its temperature to ignition point and, at some point, the decompositon to carbon creates another conducting material.

Can You Put Tissue in the Microwave (Exploring Potential Risks and Precautions) - The London Media

Putting tissue in the microwave is not recommended. Tissue, especially thin and flimsy tissue paper like facial tissues, toilet paper, can quickly catch fire when exposed to the microwave’s heat. The low density and rapid heating of such paper make it highly susceptible to ignition. Microwaves...

thelondonmedia.co.uk

 

[pedrobedro]

Our original microwave lasted over 20 years and when it went I bought Tesco's cheapest which still works but the coating flaked off the bit where the door shuts so it rusted. I relegated it to the spare room and bought one from Aldi and four years later it is doing the same thing as the Tesco one. I think I'll just paint over the flaky bit and ignore it.

 

[Onoff]

As I understand it, from some further reading since I posted, the (IF) suffix on the Magnetron dictates the mounting. I'll remake that crispy crimp as a first port of call. I wonder if another 2M253H could be got, taken apart and utilise the (IF) mounting from the original?

 

[jimbo84]

Putting any sort of tissue into a microwave is not recommended. Was the kitchen roll damp and possibly curled over at some point, especially from the steam coming from a jacket potato that's been in there for 6 minutes? The wavelength of the RF emissions of typical microwave ovens operating at 2.45GHz is 12.2cm. It's quite easy for adjacent bits of conducting material to reach quite high RF potentials, especially if there are half-wavelengths involved, and sufficient to create quite impressive arcing, especially if it's aluminium foil. Not only that, but the RF currents, induced in any conducting materials, can be quite high. With tissue paper products, even a small amount of moisture in the tissue could be sufficient for the heating effect to raise its temperature to ignition point and, at some point, the decompositon to carbon creates another conducting material.

Can You Put Tissue in the Microwave (Exploring Potential Risks and Precautions) - The London Media

Putting tissue in the microwave is not recommended. Tissue, especially thin and flimsy tissue paper like facial tissues, toilet paper, can quickly catch fire when exposed to the microwave’s heat. The low density and rapid heating of such paper make it highly susceptible to ignition. Microwaves...

thelondonmedia.co.uk

That’s interesting, I’ve been cooking spuds in the microwave for years, always sit them on a couple of sheets of kitchen roll to absorb the steam and moisture from them, 15 to 20minutes. Maybe we’ve just been lucky.

 

[voipio]

That’s interesting, I’ve been cooking spuds in the microwave for years, always sit them on a couple of sheets of kitchen roll to absorb the steam and moisture from them, 15 to 20minutes. Maybe we’ve just been lucky.

Same with @Ton-up 's other half, who has been doing the same for ages, without issue. It requires the conditions to be just right, for ignition to occur.

 

[Onoff]

A little bit of investigating just now. All measurements with leads removed:

The capacitor measures nom 1uF

Across the magnetron I'm seeing nom 0.3 ohms.

Though the clear insulating boot on the red lead to the magnetron appears scorched, the actual connection doesn't show any sign of overheating. Still a potential high resistance joint? I could solder it.

https://flic.kr/p/2qwFzJ3

I have found though the 750mA inline fuse has blown!

https://flic.kr/p/2qwFm4w

 

[Onoff]

This big diode is open circuit!

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

 

[Onoff]

Slight correction...

I read that a standard multimeter might not have enough forward voltage to check these diodes. Went and found a good 9V battery and like this got apparent continuity one way:

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