My Panasonic “Inverter” microwave, model NN-S543BF, is another example of a product made by monkeys. First of all, a year or so ago, I noticed a broken piece of plastic had fallen out of the unit and onto the counter underneath. I could not see where it came from, but I figured it would probably cause problems later on.
The microwave already had two visible signs of design problems. The backlight to the LCD display had died. There are four yellow surface-mounted LEDs behind the display. The current through them is controlled by a transistor on the other side of the printed circuit board (PCB), just below one of the LEDs, which had overheated and failed. The LEDs are in series like Christmas tree lights, so the whole display went out.
I replaced all four of the LEDs with generic parts. The (through-hole) transistor used in the LED current regulator circuit was too small for the job and got quite warm. It was mounted directly against the PCB (which had been darkened by the heat) and one of the LEDs was on the other side and just above it, exposed to the heat. I replaced the transistor with a larger one and used the full length of its leads to mount it well away from the PCB, so as not to overheat the LEDs. It's doing fine now and the display is brighter than it ever was.
My other complaint is that it blows the heat from the magnetron through the cooking chamber, presumably for efficient use of the waste heat, but it retains the odor of whatever was cooked in it last. I have to leave the door open for an hour to air it out after using it. I think the odor gets trapped in the large area between the cooking compartment and the vent on the left side of the microwave. This is an example of a good idea in theory that turned out to be a bad idea in practice. In my opinion, the intent was to use waste heat from the magnetron to help cook the food.
Finally, to replace the light bulb, you have to remove the jacket with Torx security screws that the public is not supposed to have, but are commonly available. This could expose a layman to dangerous voltages. The light bulb should be user replaceable.
This entry was submitted by Andrew Morris and edited by Rob Spiegel.
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