Question about Microwave Ovens

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Fuse blows. Drawing too much current ?cause.

Not my machine. Was told it just quit. Found a blown fuse. Had no replacement so I used a thin copper wire. With nothing in the oven sounded like it was running. As I watched the fuse became red hot. After 10 seconds before it blew the breaker tripped on the main board. Several tries with same result. Checked the magnetron, transformer, turntable motor and fan. The first 2 gave identical ohm readings as 2 other used units I had on hand. The motors function normally. No shorts detected. I dont know how to check the capacitors

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  • Thandanani Nov 21, 2008



    Hi FixYaY, There's no point at this stage in getting a proper fuse. I would need a new one every time I pressed 'start'!

    When I connected the power everything seemed to be working. The display lit up, the machine responded to commands for time settings and nothing blew. When I pressed 'start' the machine started to hum like a normal microwave. I had presumed it was working from the sound it made. Within 5-10 seconds of pressing 'start' the fuse got red hot and the circuit breaker on the main board kicked out( not the earth leakage) and that breaker is rated at 20 amps!

    I had given up on the machine until I got your message tonight and seem to have now misplaced my diagram. Hopefully I got the connections between the transformer, magnetron and capacitor right. I tried several 5 sec. bursts but could detect no change in a lump of fat placed in the oven. I noticed the transf. core already warm after that period of time. The primary was burning hot to touch. When I disconnected the HT from the capacitor of course the hum disappeared as well as the heating of the primary but what does that tell me-is there a short in the secondary or is there some other reason?

    Regards, Thandanani.

  • William Miller
    William Miller May 11, 2010

    Please get a proper fuse first.

    Let me be sure I understand...

    Is it trying to run when it should be idle?

    Please clarify this.


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  • 8,820 Answers

Wow, I've never heard of a microwave having a circuit breaker on the main board.

I would suggest that you test the capacitor and the 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

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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