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Fuse blows when I press ''Start''

Hello, I have a Sharp microwave model #R-5W38B. The other day when I was trying to heat something I heard a grinding sound and then the microwave power went out. After checking all the power connections, I opened the microwave casing and found that the internal buss fuse had blown (250v / 20amp). I replaced the fuse and attempted to run the microwave and heard a grinding sound from the top of the oven just before the fuse blew again. It seemed like the grinding noise came from the top of the microwave and so unscrewed the only part located there.
I don't know what this part is called but it has a couple of numbers on it (2M167B) & (A173). The part is square, all metal, about 4"long x 4"wide x 5"high. A smaller part, which looks like a half of a bullet sticks out of the bottom of this part. It has a positive and negative terminal at the top (facing to a side). It also has a magnet inside and a warning label on the back which states "High Voltage, Microwave Radiation".
Does anyone know why the fuse keeps blowing, what this part is called and where I can get one cheap?

Thanks,
Tom

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Okay, the part you're describing is the magnetron, and you'll not find one cheap.

The good news is that this is probably not your problem.

If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

Here are some links you or someone you know can use (in order given) for test help, but read the safety warnings first:

http://www.gallawa.com/microtech/cap_test.html
http://www.gallawa.com/microtech/xformer.html

The best place to order Sharp parts is Tritronics. You can also call them at 866-779-5835

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Posted on Nov 21, 2008

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If so, and if if it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.

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Here are some links you or someone you know can use (in order given) for test help, but read the safety warnings first:

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There should also be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

You can usually find helpful exploded view diagrams and order parts by entering your full model number here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

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If it went dead almost immediately after pressing the Start pad, that's usually a shorted high-voltage capacitor.

Here is a helpful link you or someone you know can use for test help, but read their safety warnings first:
http://www.gallawa.com/microtech/cap_test.html

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The best place to order Sharp parts in the US is Tritronics.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

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If it went dead a few seconds after pressing the Start pad, that's usually a failing high-voltage transformer.
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We're happy to help and we appreciate your thoughtful rating of our answer.

William E. Miller, AS-EET
prototech@usa.net
http://www.microwavedisplay.com

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