First the dishwasher, now the microwave… (2025 Update)

With new m/w ovens at the cheap prices they are today, repair is unlikely economic even for d-i-y.

As I said, we’re very fond of it. It’s not always about the economics.

Tim

Also, does the fact that it has lasted 43 years not indicate better build quality than any replacement?

I'd check than an internal fuse hasn't failed - age can eventually get to them without a fault.

Other than than, I don't think I'd bother with a repair at that age.

Well if “heft” is anything to go by, it’s got heaps of that! Weighs a fecking ton! ;-)

Tim

If a fuse had gone would the light come on, the turntable turn and the magnetron make hissy crackly noises?

See my other replies on that subject.

Tim

I don't know the circuit of your microwave, but it is not uncommon for just a specific part of the circuit to be separately fused.

Le 02/08/2023 à 20:07, Scott a écrit :

There is also a fan on the magnetron and a thermal switch.

Don't forget, there are some dangerously high voltages kicking around in a microwave, even after it's turned off, so I'm told.

Fan still works. My impression from the noises is that HV is being generated, but that’s where everything stops.

Tim

I’m not going to DIY this one, just after opinions as to whether repairs are *possible* on a machine of this age.

Tim

Anything can be repaired, included rusted planes from the bottom of the sea, it's just a case of time and money. In this case it sounds like something is wrong in the HT side of things, but whether it's the magnetron or something else I couldn't say. How you would find somebody trained to have a look, given the lethal voltages and currents involved, I don't know. At the least they would need HV PPE (eg lineman gloves to the appropriate voltage), since the capacitor may hold charge at HV.

Somebody here has taken apart a microwave of similar vintage:

Also to note you can buy a similar 'unused' one (the inside looks mint) for barely more than a Tesco special:

Theo

That’s a new fangled one with a digital timer. Definitely don’t want one of them. The old electro-mechanical timer and olde worlde bell are two of the best features of the old one. ;-)

Tim

Popty-ping as our Welsh cousins would allegedly say.

The primary has a slo blow fuse on it. Likely soldered in place.

Those do not normally fail for nothing.

Your fuse is still operational. The crackling tells you that, that HV is present on the oil-filled capacitor. But the magnetron has gone open circuit.

Appliance parts are not stocked for forty years. That's a bit too long.

Here is a schematic.

The magnetron has a filament. If the filament opens, no juice can flow. If the metallic surfaces in the circuit path are eroded away, no juice flows.

And if C1 arcs over, it is loud enough to knock out hearing in one ear for ten minutes (you've been warned). Arcing does not damage anything, if it happens, except your hearing. If you cook a lot of microwave popcorn, in legacy (like yours) microwave ovens, that's when an arc-over occurs. Butter&salt conduct. Normal home cooking mixes it up enough, that's less likely to happen. The machine at work, was getting one bag of microwave popcorn after another, so I suppose the result is inevitable for it. (I wasn't actually making microwave popcorn at the time. Huh.) Some of the newer microwaves have a conformal coating to protect some of it from HV discharge.

Newer microwaves have an inverter (SMPS). One of the "benefits", is power modulation from at least 70% to 100%. If you ask the microwave to run at 70%, it just drops the output voltage enough to do that. If you ask for too low of a voltage, it goes back to modulating the machine via the relay. (On for 20, off for 10. Etc)

Paul

Unlikely to be faint crackling if that is the problem.

Not possible to say unless its known what has failed and the availability of what has failed is known

My first thought is the magnetron heater has gone o/c. And the resultant increase in HT is causing the crackling but could be another failing component.

The internals of microwaves can be the most dangerous of all household devices due to the lethal voltage and power associated with that voltage.

Magnetrons are incredibly simple. With a transformer, diode, capacitor and a magnetron. Repair is easy but extreme precautions must be taken.

There are some good YouTube videos on the subject.

It's possible a build-up of dusty gunge has made a new path for the HV, so give it a good clean inside with IPA.