Question about Panasonic NN-S543BFW Microwave Oven

1 Answer

Blows line fuse

Unit is approx 3yrs old; the magnatron was replaced under warranty w/in a few months of intial use. The symptoms are: magnatron shows no resistance to casing, filament is not open (measures less than .3 ohms), no visible signs of arcing, had recently shown signs of intermitt door swith - could have been physical latch/position failure as pushing on door harder was good remedy. Never really cared much for this oven - it was a gift. The oven this replaced was a Gen-Air/Amana? that was built like a tank, & lasted approx 15-20yrs. It's the only device in my home that causes interference in bluetooth audio devices - probably from the inverter ckt. If I could confirm a defective magnetron, it's dumpster fill!
Any advice?

Thanks,
R. Munn

Posted by on

  • Richrad D. Munn Mar 28, 2008

    After reading the notice on top of the cook cavity, I suspected there might be a problem w/the interlock or monitor switche(s). The notice says all four safety switches must be replaced if the line fuse is blown due to a defective monitor switch - a bit OSHAish..., but supports the possibility of a misaligned or defective switch causing the line fuse to blow.

    I purchased a Sharp Carosel oven today, and will check all of the switches in the Panasonic before giving up on it - will probably keep it for a spare if it is a switch. This particular Panasonic does not have the usual HV "can type" capacitor, & the two HV diodes check OK. I'll post the outcome when I have a chance to bench it again.

    Thanks for your input - it squares w/what I was thinking.



    Regards,

    R.Munn

  • Richrad D. Munn Nov 30, 2009

    I recently got back to the job of repairing the oven in question - just couldn't bring myself to toss it. After all, it is one, if not the only, oven that actually adjust the magnetron output level for percentage cooking, rather that proportionate on/off cycling. The problem I found was a shorted IGBT on the inverter board (Mouser p/n 757-GT60N321[Q]). The cost w/shipping was about $18.00. I replaced that & the open 18amp type abc fuse and all is well. BTW, This oven needs a 20amp house ckt for proper operation.

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Check the resistance of the capacitor across the cap terminals and to ground. It should be open. Also check the diode for a short. Lastly, on some models a defective or misaligned door switch can blow fuses.

Hope that helped...

Geno

Posted on Mar 28, 2008

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