Repairing a Samsung Micro-wave Oven

Don't you hate it when the thing you just bought goes "kerplunk!" on you? On top of that, something you chose very carefully, taking into account price range, ease of use, size, etc.?

Well, this happened to me with this Samsung micro-wave oven. I wanted something simple even my mother and mother in law could handle (they come to my house to look after my kids when I'm working). I wanted something durable, simple and that gets the job done. This is why I chose this simple Samsung micro-wave oven, with just two knobs: one for setting the power, the other for setting the time. That's it. No complicated panel with lots of blinking lights and different types of beeps. And cheap, too (around 90 euros). The old one was still working (a Samsung too, btw), but the inside paint was all chipping away (that can't be good, right?).

Well, I don't know if Samsung is not as good in quality control as before, or if I'm doomed (the micro-wave before this one never worked), but this thing just stopped working properly after only 6 months! The power know got stuck around mid-way, which means it took forever to heat anything with this faulty micro-wave oven.

It was obviously just a faulty controller issue, as the magnetron, and everything else seemed to be working just fine.

If this has happened to you, and you're wondering whether you should get a new one, or try to repair the one you have, here it is: how to repair a faulty Samsung micro-wave oven.

Step 1: Setup

For this project, you will need the basic tools to open your micro-wave oven.

SAFETY WARNING: OPENING A MICRO-WAVE OVEN IS DANGEROUS, HIGH VOLTAGE HAZARD

BE SENSIBLE: DON'T KILL YOURSELVES, DON'T SET FIRE TO YOUR HOME

Dealing with the insides of a micro-wave oven is tricky: the magnetron needs high voltage to run. This high voltage is delivered through a large capacitor. So don't fool around, pay attention to basic security measures when dealing with high voltage power.

First, get some psycho-active stimulant. For me, it's tea (smoked tea from Malawi), but you can use whatever suits you. Since you'll be dealing with high-voltage and electronics thingies, you want to be sharp. Not too sharp: you don't want to have shaking hands.

Then, the basic tools: screwdrivers (a small one is good for dealing with screws in cramped areas), magnifying glasses (that's always useful when dealing with electronics, especially when your eyesight is getting weaker after 40). Some light will be useful too. And don't forget to magnetize at least one of your screwdrivers (touch it 5 times to a strong magnet): tiny screws have a way of getting stuck in hard to reach areas. Don't magnetize screwdrivers you use for your computer, though.

The most important item of this project is the controller. Since in my case, the problem was very obviously due to a faulty controller, I decided to get a replacement (from the web, in my case, from a French vendor but spare parts are available almost everywhere). I therefore had to open the micro-wave oven, get the reference for the spare part, find a website that had it in stock, and buy it. In my case, I managed to find the exact same controller as the one in my faulty oven, it cost around 30 euros, and it shipped within 5 days. You might salvage a controller from a used micro-wave oven, but these things are really custom PCB boards with a lot of tiny tiny electronic gizmos on them. So, if you don't have a spare controller, I don't see how you could get your device to work.

Step 2: Spare Controller

In my case, the controller is shown on the picture. These things are pretty much Lego(TM) like: they are pretty easy to install. If you've already messed around in your PC, this will be pretty easy. I must say I was pleased with how the cables and parts were organized. I've tried to repair other devices in the past, and with some of them, I didn't even know where to begin.

Step 3: Opening Your Micro-wave Oven

OK, so you have everything you need, and your device is now unplugged. So, you think, what could go wrong?

Be extremely careful when dealing with micro-wave ovens: they use a very large capacitor (as shown in the video) for delivering high-voltage to the magnetron.

As with all large capacitors, once you've unscrewed the outer case, you must be extremely careful.

DO NOT TOUCH ANY EXPOSED WIRES

DO NOT TOUCH ANY CONNECTORS

DO NOT DISCONNECT ANY CONNECTORS

First, you need to discharge the capacitor. Just because it is unplugged doesn't mean the capacitor has no residual charge. You need to take care of that high voltage before doing anything else. The best way to do this is to use insulated wire and make some sort of "jumper" with it. Cut around 20 cm of insulated wire, expose around 1 cm of wire at each end. You need to be very careful and to touch only the insulated part of the wire. Now, touch one of the ends to one of the capacitor's connectors, and touch the other end to the other connectors. You should see a small spark (and you should hear it, too).

Once this is done, you can proceed by unscrewing the controller. In my case, the controller comes in two parts: the user interface, with two knobs, and the controller proper, which drives the fan, the lights, the magnetron's cycles, etc.

It's pretty easy to see where and how everything is screwed on. You first need to unscrew the main controller, in order to have access to the user interface.

Step 4: Detaching the User Interface From the Main Controller

Once everything is unscrewed, you will see that the user interface is connected to the main controller by a flat wire shown in the pictures. You need to disconnect that (gently: don't twist or tear that bundle of wires).

It's a good idea to take good quality pictures of the setting before doing anything, so that you can put everything back into place.

Once the user interface and the main controller are disconnected, (second picture), you can take it out of the case. As you can see, there is some shielding (the tin-foil like sheet) on the user interface. Don't mess with that.

You can extract the knobs by pulling gently. Keep them in a safe place, you'll need those later on. In my case, there are two distinct knobs: one for the timer, the other for the power. Make a note of which is which.

Step 5: Keep Your Fingers Crossed...

After you've swapped the faulty controller for a brand new one, you need to put everything back into place.

As I said earlier, if you have the right parts, it should not be a problem, it's mainly a matter of connecting the right parts in the right places. The only tricky part is figuring out which screws go where. And managing to tighten screws in very hard to reach areas (without touching exposed wires, just in case).

Once everything is back into place, you can test your device.

For this, it's always a good idea to keep a glass full of water in your micro-wave oven. Oh, and maybe get the cover on (I tested it without the cover on, apparently the micro-waves are channelled through some kind of cheap tin-like "funnel").

And you also want to keep your fingers crossed!

You also want to make sure that you don't put the plastic knobs back before making sure everything works as intended. In my case, I had to unscrew everything, fool around with the power knob before getting the oven to work properly. Apparently, there are different settings on the user interface PCB board: one is "always on", and another seems to be "always off". The rest is standard "defroze", "medium", "high", etc.

Step 6: Enjoy

If everything is back into place, and the knobs are just so, once you plug your oven back on, it should work.

In my case, it took some tinkering with the power knob to make it work.

But in the end

IT WORKS!!!

No more frustrating moments waiting for the food to warm. You'll be able to use your micro-wave oven to its full potential again. Personally, I use it a lot for:

• defrosting meat
• steaming vegetables
• steaming rice (Tilda basmati rice comes out great in the micro-wave)
• steaming fish
• making pop-corn
• making fat-free poppadoms and shrimp crackers in a jiffy
• etc.

Now, was it worth it? Wouldn't it have been easier to just dump the thing in the junk and get a new one?

Well, I hate to waste. I mean I stay up at night thinking about all that waste. From wasting food, to wasting water, electricity, gas, or anything else. Also, I can't stand programmed obsolesence, and bad engineering. So, once I realized it was only a matter of getting a new user interface PCB, I just couldn't let this otherwise perfectly functional device go to the trash.

All in all, I spent around 4 hours on this project

• locating the right controller for my micro-wave oven: 1 hour
• finding a reliable website (they don't sell parts in stores): 30 min. (shipped in 5 days)
• swapping the faulty controller for a new one: 2 hours
• putting the casing back on, testing, cleaning up: 30 min.

I was very careful, since I didn't want to have to deal with high-voltage issues. And I was stopping to take pictures all the time.