Question about Sharp R-4A58 Microwave Oven

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In the middle of cooking frozen dinner, instant death..

My Sharp R-4A58 simply quit after cooking about 40 seconds. Everything went dead, the clock, light, nothing worked. I figured it was a fuse, so I changed it, plugged it back in and reset the clock, set it for 10 seconds, pushed start and it took off, but only for less than 2 seconds, then all died as if you pulled the plug. I read the post by Iggi on Nov 12, 2006 and basically, aren't most microwaves about the same? Could it be one of the three (HV Capacitor/Diode, Transformer or Magnetron) and if so, how do I go through the process of elimination, cost effectively? I've had this thing since (new out of the box) I think in 1995 and surprisingly, it's still almost that clean, even around all the electrical components. No signs of electrical burn anywhere either. Any other info I need to give for a recommendation to what might be the problem, let me know.

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Re: In the middle of cooking frozen dinner, instant...

We have *critical* safety, disassembly, and troubleshooting info at our site, which is linked at our listing here on FixYa: If the fuse blows a few seconds after you hit START, then it's likely that you have an overheating / shorting high-voltage transformer. Try this: Let the oven set unplugged for about an hour to cool completely. Then cook for a minute at the lowest power level. If it runs any longer than it has been, it's probably the high voltage transformer, which is no longer available, but will run about $95 if you can find new old stock. If the fuse blows as soon as you hit START, then it's likely that you have a shorted high-voltage capacitor (#RC-QZA211WRE0) which runs about $25. You can order parts for Sharp models from Tritronics at

Posted on Sep 22, 2007

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