Burnt electrical “item” in power board – need help knowing what is it called

I got a 120v coffee maker back with me from US to where I currently live where they use 220v.
I got with me a 1600w step-down transformer from Radio Shack (the machine is 900w) but it seems that it was faulty because when connected to power, the coffee maker "popped" and smelled like burning plastic.

I decided to give it a shot and see if i can fix it. I reached to the point of locating the problem which is a burnt blue rounded electronic item (sorry I'm a Network Engineer not electrical, so i know only what capacitors, diodes & resistors are lol).

Anyway can you have a look at it and tell me what is its name so i check in the market and replace it if it is replaceable. What's your advise?

If I'm not mistaken the device you have is not a Transformer, it is Voltage Converter. It is designed for use with resistive heating elements only and can damage devices having electronics, such as your coffee maker.

The visibly damaged device appears to be an MOV (Metal Oxide Varistor) used to clamp voltage spikes. The Voltage Converter probably applied voltage high enough for the MOV to conduct and it burned up.

If you have access to 120 VAC you can remove the MOV and check to see if the circuit works correctly. If it does work correctly the MOV can be replaced with one rated for 120 VAC or it can be left out of the circuit at the risk of the circuit being damaged by a voltage transient.

So you are basically saying i need to test the circuit first with 120VAC to see if it wasn't damaged?

The label writing on the MOV is gone as you can see, so if i want to replace it, do MOVs come in specific shape/color/size for each model? Because I want to buy it online (I couldn't find a decent electrical shop in here), but i'm looking around the net and I noticed that they are different in shape, size and color, similar to the fuses used in car fuse box. I need an expert's advice before purchasing anything that is useless for me.

And you're right, it is a voltage converter

Well, you will need a source of 120 VAC not only to test the coffee maker but to run it everyday.

To find a suitable MOV find one that is has a rating of 130 VAC and is about the same physical size.

The MOV was in the circuit to enable it to pass the UL line-to-neutral transient test. This test is an RC network that discharges 0.3 uF charged to 800 volts.

This link to Digikey is for a suitable MOV.

http://www.digikey.com/product-detail/en/MOV-10D201KTR/MOV-10D201KTRCT-ND/2408231

Here is the datasheet.

http://www.bourns.com/data/global/pdfs/MOV10D.pdf

120 VAC is needed to operate your coffee maker and a transformer is the device to use. The travel converter, I believe, chops the 240 VAC waveform so the RMS voltage is 120 VAC yet the peak voltage is still the peak of 240 VAC (340V peak). This works for resistive heating elements such as the heater in your coffee maker but does not provide the electronic control board with the 120 VAC (170 V peak) it needs.

I don't know how to thank you enough for the information and the time you took to explain what's going on. Really thanks a million.

I have purchased 5 MOVs (keep 4 for spare lol) and i will go back to use the huge box transformer I bought from ACE Hardware when we first got the coffee maker. Thinking that Radio Shack voltage converter would save me space on my kitchen top instead of the transformer box proved to be a wrong idea! But the most important thing is now I know why; thanks to you! Will let you know how things go once i receive the parts, that's the least i owe you.

It's true when they say: If it ain't broken, leave it alone!

Hello David,

Just want to tell you that the coffee maker is kicking alive again! Thanks a lot for all the help I really appreciate it.

Ahmed, that's great that you can drink coffee again! I'm having a cup right now.