A shorted cap gets hot, so after a minute switch off, pull the plug, and check for hot parts with a fingertip. It does work, usually.

True. But if it IS a SMD chip knowing the value will be impossible. If it's just a filter cap that's pretty easy, but if it has anything to do with timing - value becomes critical. Since "Nothing happens" is the report along with getting very hot - I'd think something is shorting across the power rails or may be shorting something through the chip. Bottom line, the chip should not be getting hot. And if it is a timing cap then it might or might not be getting hot.

Then there's the dilemma of changing it. Can be difficult for a beginner. Even I try not to tackle SMD components - especially those darn small ones.

 

Then there's the dilemma of changing it. Can be difficult for a beginner. Even I try not to tackle SMD components - especially those darn small ones.

I made some small boards to mount four P MOSFETs in SC-89 with pull-up resistors on the gates. I used solder paste, but applied it with a wire. It made what appeared to be good joints, but I found that some connections opened up after operating for a few hours. I had to do several iterations of applying more solder and running them long enough for problems to develop.

 

If we're talking about a microwave oven - are they that expensive in Italy? I can pick up a cheap one for around $50 (US). I've picked up quite a few others have thrown out. I have one in the basement with a bad control panel (the buttons). If I want to fix that it's a pretty easy proposition. I have one in the garage that works perfectly. Of the others I've had, scrap metal has been the fate of most of them but I've kept a few control boards. One project was to use the control board to power an outlet. I can plug my soldering iron into the outlet and power it for up to 99 minutes and 99 seconds. I do that because I have a propensity for turning it on and forgetting about it for quite a while. If I know I'm going to run it for 10 minutes I can set the timer. Otherwise, aside from the MOT and the magnets from the magnetron there's not much use for things. Unless you need a turntable that turns 6 RPM.

What I'm saying is "Why not just buy a new machine?"

Yeah, I know the thrill of fixing something. I've done that plenty of times. In fact, my neighbor just threw out a quad copter (really cheap one). But it has a nice 720P camera. The tiny motors - don't know what I'd do with those, but I even have the controller. Maybe I'll see about fixing it. But I don't have a battery or a charger. 3.7V Li-Po battery. Cost on Amazon is $8.49 for two 3.7V 500mA batteries. I don't know why they tossed it but it's now in my possession. Along with the µSD memory card (and videos of crash after crash).

 

Be careful that you don't radiate yourself. Some things just aren't worth messing with,

 

If we're talking about a microwave oven - are they that expensive in Italy? I can pick up a cheap one for around $50 (US). ...

What I'm saying is "Why not just buy a new machine?"

You all make interesting points... There are four reasons Ive ben wanting to repair it.

First of all, oven cost me around 1000 Euros 10 year ago. Its the predecessor of this one

https://m.ebay.ie/itm/Smeg-SF4390MC...ation-Microwave-Oven-/321944946254?nav=SEARCH

is still basically new, used sporadically for about two years overall, and it cooked really well (when it worked).

Second, i was quite picky at the time and bought all kitchens appliances of same brand and style to match.

Third the thrill to repair it (or maybe the first reason)

Finally, having a very small kitchen I really have no room for a free standing microwave. This oven is a combined one and can work like a traditional oven... Is fitted inside the kitchen cabinet. I Have a very small working area unfortunately.

I posted a message earlier but for some reason didn't send. I was going to ask about SMD capacitors but I got the answers from your messages anyway. I thought that maybe, if I were able to find a faulty one, I would be able to find out its value maybe by measuring it and by colour... But I think to understand that's not that easy. And no, none of them get hot...I already tried.

To tell all the truth, I gave up trying to repair the board maybe a year ago... And set up an Arduino board with a set of SSD relays to do the desired switching, a nice display and reuse all the safety features (interlock switches and safety thermostats) of the oven. I spent quite some time coding it on my spare time then got stuck with temperature measuring as it's trickier than I thought... Needs a lot of calibrating as temperature inside the oven is different depending where measuring it... Long story short, I decided to give it another shot, maybe if I were able to restart the control board even if only for a while I could do many tests to go different paths. I even thought about purchasing an off-the-shelf power supply to reuse the original PCB... If only I was able to test all the voltages of the transformer and had more cabilities with electronics.

Anyway, thank you all for your help, if you LL never see me again on this forum probably I got microwaved

 

if you LL never see me again on this forum probably I got microwaved

We hope to see you again and again and again. Be careful. Be safe.

The first thing to be affected by microwaves is your eyes. They cook like eggs. Or so I hear.

 

One more thought is to stay on watch for another oven of the same kind that may have a failed magnetron tube or some other such, but a working circuit board.
There certainly was a lot to be said for those mechanical timer microwave ovens. I had one that lasted about 30 years and still worked when my family insisted that we get a more modern one. Now we are on the third one in ten years and this time it is a Panasonic and the door hinges are wearing out so that it takes an effort to close the door so that it latches. Such quality???

 

We hope to see you again and again and again. Be careful. Be safe.

The first thing to be affected by microwaves is your eyes. They cook like eggs. Or so I hear.

 

I don't operate the magnetron unless the cooking chamber is correctly closed, and I always keep shielding between me and the system. Thus I do maintain a safe condition. Also, most of the parts that need servicing can be adequately checked with the power off.