Microwave oven - bizarre circuit??

[gallowfields]

it is quite common for the hv capacitor to s/cct .it is also best to replace the hv diode [for the cost of them] a lot of the more recent ovens also have a hv fuse from the transformer to the cap .only last week had exactly the same happen to our 6 year old bosch one .we used to repair lots of microwaves for private customers as well as manufacturers

[Andrew B]

When I have repaired my OLDE microwave, I have found that it's the heater/kathode that has gone short to ground, now on it's 3rd second hand magnetron in 12 years. The replacement magnetrons were taken from scrappers of unknown ages/history.

[mickm3for]

Hi danger taking the magnatron to peices,as Most magnetrons have beryllium oxide (beryllia) ceramic insulators, which are dangerous if crushed and inhaled, or otherwise ingested. Single or chronic exposure can lead to berylliosis, an incurable lung condition the same for some RF output transistors Mick

[GMB]

Originally Posted by gallowfields

only last week had exactly the same happen to our 6 year old bosch one

That seems to endorse "they don't make them like they used to". I view anything less than 10 years old as "new".

It raises the question as to how far back one has to go to find that a branded product was actually made by the company concerned - themselves - rather than having it all subbed out to China.

[G6Tanuki]

Another feature of the design of the microwave oven transformer and rectifier relates to the magnetron heater.

It is a problem with magnetrons that at full power the cathode is subject to back bombardment which will cause it to overheat unless the heater power is reduced to compensate. The transformer is designed so that at switch on when there is no HT current being drawn, the heater voltage is the normal value but when the magnetron is up to temperature and starts to draw HT current the saturation effect in the transformer leads to a reduction of heater voltage which accommodates the back bombardment.

Cunning, but now obsolete since microwave ovens now use inverter power supplies which are lighter and more efficient

[Radio Wrangler]

Not quite so obsolete.

My old AEG built-in combi started failing and it looked to be the microwave transformer primary. So I needed a new cooker.... but one of the right dimensions to slot into the existing space. After rather a lot of searching I found one. Also an AEG, but unfortunately it was a top of the line model and thus badly overpriced it was a new model and supplies were only just starting. So I bit the bullet and went to my usual supplier to get one ordered. A couple of days later they contacted me saying they'd had an email from AEG declining the order because only a small list of dealers were allowed to order those! What? a manufacturer blocking their own sales? So the search went on to find somewhere that could order one. Eventually one got ordered and I went and collected it earlier in the day that lockdown first started.

Did I say it featured internet connectivity? It didn't feature any explanation of why I should want to enable this. Triggering a microwave cooker remotely sounds stupid, and having it open to all the black-hats of the internet is beyond stupid.

Anyway, a latest, top line model, and it has a damned heavy transformer....

David

In the avionics job, I had a lot of dealings with RF power semiconductors and the firms making them see solid-state microwave cookers as the next big thing. So far they have 300W output devices on 50v DC supplies and are thinking of multiple RF paths.

[GMB]

Originally Posted by Radio Wrangler

Did I say it featured internet connectivity? It didn't feature any explanation of why I should want to enable this.

I would hope that was a diagnostic feature, so only enabled when it is broken - - - OK I can see snags there.

Our new* washing machine has the same idea but is hacker-proof. That is because it does it using an accoustic modem (incredible that the idea of doing that is still remembered). So the only way it connects to anything is if you stand there holding a phone up to its speaker.

( *GMB defintion of new. It may be older than I think).

[G6Tanuki]

A lot of people would see an old built-in microwave oven starting to fail as the ideal excuse to bring forward the obligatory once-in-a-decade kitchen replacement.

My current microwave/groll/combi-oven thing I bought in 2007 when I moved here; it's silver and replaced a 3-year-old one which was white. White did not match the rest of the appliances in the kitchen so it had to go.

After 15 years of relatively light use it's starting to get a bit shonky. I'm looking at a kitchen refurb.

[GMB]

Originally Posted by G6Tanuki

once-in-a-decade kitchen replacement

I do not understand this. We only ugrade a kitchen when we buy a house and we are on our second and last one. So our new* kitchen is about 30 years old, but the microwave and main oven came from the old house so are much older.

Now I think about it, the microwave is the only one we have had in our main house.

[G6Tanuki]

My existing kitchen is 16 years old. Showing signs of wear - burnmarks knifemarks and dents on the wood worktops, some cracked floor/wall tiles, appliances with the lettering worn off the controls, questionably-accurate thermostats, cabinet doors no longer closing smoothly. It just _looks_ tatty, tired and so very early-21st-century. I need more power-outlets too.

Not sure if this time I'll go for a combi grill/oven/microwave though.

[Cobaltblue]

I think the OPs original queries have all been covered its time for the little ding to sound on this one.

Cheers

Mike T