View single post by iceman
 Posted: Mon Apr 25th, 2005 01:59 am
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Joined: Wed Apr 6th, 2005
Location: Uzbekistan
Posts: 76
Hi Seven,

You raise two good points:

1) Can we cut the Panasonic engineers some slack, since they should be recognized for attempting to improve microwave technology by employing modern advances in semiconductor power electronics and, after all, nobody gets it 100% right the first time?

2) Isn't iceman's microwave a special case because it is in a harsh environment?

Regarding the second point:

The Panasonic Microwave in question lived in a special hood-fan cavity that was designed to hold a (very large) microwave. It replaced an even larger Toshiba whose uP power supply went out of regulation rendering it insane but still capable of cooking, just randomly. The oven heat and cooking gases were routed on either side of the microwave cubby hole in special integral ducting in the hood fan unit, and were expelled back into the room 10 inches above the microwave, after passing through two sets of coarse, then fine filters above the microwave oven (one set on each side of the microwave). There was an air gap of approximately one inch on either side of the microwave between the microwave and the ducting and about 5 inches above the microwave. While it is possible that would result in elevated temperatures in the vicinity of the microwave cubby hole, the temperature in that locale was never more than 5 to 7 C above ambient. Also, the microwave was rarely operated at the same time as the stove. The microwave outer surfaces never became contaminated with grease, so I am reasonably confident that this was not a contributor to internal contamination. I have also visually verified this by bringing a special TORX driver with a hole in the center to remove the tamper proof screws home from the office and opening the oven up to survey the damage. Conclusion: no particularly harsh conditions existed in the operating theater of the defective microwave oven.

Regarding the photo, I would love to, but I have recently moved and while the microwave accompanied us, the hood fan unit did not. The hood fan unit was manufactured by Broan in approximately 1977. I have tried to find a picture on the internet, but have not succeeded. I realize now what a unique piece of equipment that was. For example, the fine filters had actual charcoal particles in them.

Regarding the first point:

I applaud Panasonic's attempt at innovation. I am all for miniaturization (except in two specific cases that come to mind) and I am all for advancing the state of the art. However, I also work for a large corporation, and I have worked in a consumer electronics division in that corporation for a period in my career about seven years ago. The name of the game in consumer electronics is cost-reduction, in fact that is the game in every division now. Cost reduction design is where the men are separated from the boys. Any knave can reduce the cost of a circuit, but it takes a master to do so while retaining the same features, and level of quality. One of my colleagues event added functionality on one of our products while cutting the cost to one quarter, when others scoffed and said he was doomed to fail!

More importantly, if the warranty return rate exceeds say 5%, then you know you have a design problem, and responsible companies take action to rectify the problem. Finally, if the design problem is causing fires, that usually gets lot of executive "help" in addition to the regular "support" from product management.

This is the purpose of my post. Do other owners of Panasonic Inverter technology have the same experience as I, or are the four instances of failure I am aware of simply statistical outliers?

I don't know, so at this moment a more reasonable chap might be unbiased. Perhaps it was premature for me to insult the honorable Panasonic design engineers, but in my books, if three-five years elapse and the problem is still not fixed, someone is asleep at the switch, or worse, negligent!

Perhaps I am being a little overly defensive. When I was ten years old some roofers near my house called me a paranoid little weirdo - in Morse code!

That has always stuck with me...


Last edited on Mon Apr 25th, 2005 02:05 am by iceman