• Whirlpool and obsolescence

    Alan Liefting

    A Whirlpool VT256/SL microwave oven came in for recycling this week that looked like a good candidate for refurbishment.  It was dead. It had a blown fuse and a shorted high voltage capacitor in the voltage doubler circuit.   So I replaced the blown bits and it ran up sweet.

    And then I checked out the waveguide covers because they sometimes get a bit carbonised and start arcing.  We sell a lot of them through our online shop (sorry about the advert but hey you are getting a free blog post!)

    This microwave has two mica waveguide covers – one at the top and one at the bottom.  Most microwaves only have one.

    So take a look at this photo.

    whirlpool-vt256-burnup

    The carbonisation happened around a bead of glue that goes across the waveguide cover, probably due to food residues getting trapped on it.  Now take a look at the wall of the cavity above the waveguide cover.  For some reason there is an extra level of indentation between the waveguide cover and the cavity wall.  Why?  And what does the glue do?  Is the bead of glue in the wrong place? Should it have been  acting as a sealant in the wide gap between the waveguide cover and the cavity wall?

    I don’t think it is a deliberate ploy to create inbuilt obsolescence.  The Whirlpool microwave ovens are generally built quite well.

    I have come up with a decent fix for it so if you need one buy one here!

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  • Bang!

    Alan Liefting

    This photo shows what a power surge can do. The fuse in this microwave oven absorbed so much energy that the end cap of it completely vapourised and shunted it along the fuse holder.

    A photo showing a 20=5mm ceramic fuse with a vapourised end cap.
    Bang!
    (check out the hardware bug)

    The body of the ceramic fuse remained intact which is what it is supposed to do

    It looks like the power surge was between live and earth because the capacitor (next to the fuse in the photo) had a very small eruption visible on its body.  It measured as 4nF and it is supposed to be 4.7nF.  The corresponding capacitor on the neutral side of the filter measured correctly as 4.7nF.  They are an X1/Y2 rated capacitor (as what would be expected) and it looks like it took the surge pretty well.

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  • Patently obvious

    Alan Liefting

    I was doing some searching on the internet for images of microwave oven parts when good old Google offered up this patent in amongst the search results. It was a patent for a method of wiring up microwave ovens filed in 1998 by Samsung Electronics.

    It is for something that is, well, patently obvious.  Take a look at these images from the patent:

    Yeah, I agree.  They want to patent that?  A really simple wiring change? It is like patenting a paper clip. Ah…  I see that it has a patent.  From way back in 1897. Come to think of it didn’t I hear about some sort of simple clicking on a web page that is covered by a patent?

    The good news about the microwave wiring patent is that in 2000 someone had the good sense to throw the patent application out.  I now know that I can sleep soundly after rewiring microwave ovens safe in the knowledge that I did not illegally flout someones patent.

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  • Don’t snort your crushed microwave oven

    Alan Liefting

    NOTE: Some information contained in this post is incorrect.
    See the comments for further information.

    Here is a little bit of advice.  If your microwave oven is crushed into a pile of dust and shredded metal you should not snort it up your nose.  Bits of it are poisonous.  The magnetron, which generates the microwave energy, has a sintered ceramic insulator that is made from beryllium oxide.  During use it is inert and harmless but if it is crushed and the dust is inhaled you can get berylliosis, an incurable disease of the lungs.

    There are other electronics items that contain beryllium oxide as well as other nasties, so to be safe make sure all of your e-waste is recycled.  Here at Ecotech Services we can fix or safely recycle your microwave oven of course. Or we can recycle just the magnetron. And other types of e-waste.  Give us a call.

    The pink section just below the waveguide at the top is made of beryllium oxide.
    Image: Wikimedia Commons.

    [Edited 13 August 2015]

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