Potential Problem With Older Microwaves

Automatic Washer - The world's coolest Washing Machines, Dryers and Dishwashers

Help Support :

Panasonic Dimension 4 Combis

According to the parts drawings and owner's manual I've seen for the Panni DM4 there isn't an exposed heating element. Just a grille cover on the inside top of the oven but nothing the exposed elements one is used to seeing in electric ovens and or broilers.
 
They dont use a calrod element for the grill, most of the Japanese designs use a Quartz element (Kind of like a bar heater element) that is mounted behind the grill. It then relies on the turntable to rotate the food under the element. The Element is the hour hand from the centre to the outer edge and the food rotates under it. It doesnt heat the entire top of the microwave, only the one specific area.

The claim they make is that its isntantly hot and not reliant on heatup time compared to the traditional calrod.
 
My Whirlpool Mico/range hood, a G3, has a halogen as well as an infrared element for broiling.  I would not broil a steak with it, but I enjoy my chicken broiled and microwave cooked with it.  The skin gets nicely crisped and brown and the inside is fork tender.   I put a Maytag Micro/Convection/oven/broiler in the house I redid a few years ago, was looking for top $$ for the place but the market crashed and I rented it out.  When the folks move out I'll pull it and pop in a cheapie and either save it for here or swap out the one I have.

 

There are times a small oven would be perfect.  I'm not lacking for ovens, I have 3, but they are all standard sized and at times  a quick pan of cookies or such would be nice with out running the big oven.
 
SLOW TO COOK MICROWAVE OVENS

Cory is correct, in my experience MW ovens do not slow down much over thier life time. Magnetron tubes do fail and when they do it will be a dramatic slow down of cooking speed or non at all. The worst thing you can do to your MW ovens Mag tube is to run it empty or nearly so. This is why so many mag tubes fail while trying to pop pop corn as there is very little mass to the PC and you are running the oven at full power trying to heat it. Also in our experience the newer over 900 watt MW ovens are having many more failures of the Mag tube. The tubes in the newer ovens are the same size but they are working them much harder and this seems the cause them to fail faster. The newer ovens are more efficient however as they do put out more cooking power while using about the same amount of electricity as the older 600-700 watt models, but sometimes at the expense of long life.
 
Did some more reading.

The consensus (if the Internet can host such a thing), is that magnetron tubes can lose some of their power, but the slide is relatively small and probably undetectable by consumers.

However, the power supply (transformer) can lose its effectiveness. One poster opined that the most common way this happens is if the capacitor loses its ability to store power. This would result in the magnetron going into a pulse rather than a continuous power mode, resulting in lower average power output.

I figure the power supply/capacitor issue is probably what I've observed in heavily used older microwaves in the company lunchroom.

Another post suggested that one can measure the actual power output of a microwave oven by heating 500 ml (1/2 liter) of water for 60 seconds, measure the temperature rise in C, and multiply by 17 to get effective watts.

No I haven't tried it... yet...
 
MICROWAVE OVEN POWER LOSS

 I do not believe that anything can or does happen to the power transformer, that makes no sense at all. That would be like an induction motor losing HP I have never heard of such a thing. The capacitor losing value is something that I am not as sure about.

 

MW oven power output is tested by how much it will raise the temperature of a given quantity of water in a given time. The manufacturer-or publishes this information in thier repair manuals for specific models, so it is easy to test.
 
It seems possible to me....

Read on...

"It is possible for a microwave to lose cooking speed. If the microwave source isn't able to produce as intense microwaves as before or if it doesn't turn on reliably and steadily, it won't cook as fast. For the source to produce less intense microwaves, the high voltage power supply would probably have to be weak. Its storage capacitor could have failed or one or more of its high voltage diodes could have burned out. According to a reader, the most likely cause of weak cooking in a microwave oven is a failed capacitor—with no ability to store separated charge in its capacitor, the oven produces pulsing rather than steady microwaves and delivers less average power. I suppose that the magnetron itself could be dying, with the most common failure (according to that same reader) being shorting out, the result of electromigration of the filament material. For the source to not turn on reliably, it would probably have to have a bad connection to the power line. One good possibility is that the relay that turns on power to the high voltage power supply is not making good contact.

"Listen to the microwave as it operates on a medium setting. It should cycle on and off every five or ten seconds. You should hear it hum softly during the on half of the cycle and then stop humming during the off half of the cycle. Different power levels simply vary the fractions of on time and off time. If you don't hear the hum or the hum is intermittent, then something is probably wrong with the power relay or with something else in the high voltage power supply. If the relay is flaky, a little cleaning of its contacts may cure the problem. Be careful of the high voltage capacitor, which can store a lethal charge even when the unit is unplugged."

http://webcache.googleusercontent.c...d=1&hl=en&ct=clnk&gl=us&source=www.google.com
 
In modern microwave there may not be a relay to control the primary power to the transformer-maybe a solid state circuit instead.Both tubes and capacitors do lose capacity.However if the capacitor or transformer has failed-usually shorted-blows the fuses inside the microwave.another thing on the magnetron-its magnet can lose magnetic power from the heat of the tube and other parts in the oven.this is minor-but can happen-Its more common on very high power radar transmitters.Microwave oven transformers rarely fail on their own-something CAUSED the transformer to fail-like a shorted cap,diodes, or tube.
 
And yes,running the microwave with no load can lead to short life of the magnetron tube.The magnetron tube has a short antenna like probe inside one end of the tube-connected to the waveguide that directs the microwave energy from the tube to the oven cooking chamber.Now if theere is no load to absorb the energy the magnetron generates-the little antenna probe heats up-and even overheats-this causes the glass seals on the probe output end of the tube to fail.-tube goes to air.end of tube.the no load condition may take some time for this to happen.
 
The 1978 Popular Science article was interesting. I remember when microwave ovens became widely available, there was a lot of concern about radiation escaping. People would try to avoid standing directly in front of one while it was on.

Further in the magazine, I also enjoyed the ad for the 1978 Ford Fairmont! While not a particularly exciting car, it was sensibly sized, fairly roomy inside and it was easy to park.

And I also enjoyed the ad for Winston Light cigarettes!
 
If you've ever driven one of these, you would agree that by comparison, a Fairmont is a breeze to park, LOL. In 1978, the Fairmont was positively petite. From there you got bigger with the Granada, then huge with the LTD II, and then gargantuan with this LTD Landau 4-door pillared hardtop.

retropia++6-30-2011-12-39-11.jpg
 
Combi Units

Was reading through an older issue of the CR Buying Guide (1983) and in general they panned combination microwave/convection ovens of the day. Of the choices (Sharp, Amana, Panasonic, Quasar), the Radarange (RMC-30) came in dead last in both microwave cooking and combi roasting beef. Apparently according to CR's tests neither the Quasar nor Amana produced even cooking with microwave power only (note these were the only two models tested without turn tables), and had various drawbacks to their convection/combi modes as well. The Amana for instance had only one preset temperature, 300F.

From reading vintage microwave service information on the web, Amana knew for awhile it's combi ovens had too low power for browning/baking. The initial models (RMC-20****) had heating elemets of only about 1300 or 1400 watts. By the time Amana changed from the Cookmatic series with dials to the Touchmatic, the new combi oven (RMC-30) had wattage bumped up to about 1500 watts.
 
Nabbed A Bunch of Vintage Consumer Reports Buying Guides

According to their testing, which counters what one finds here in the group, Amana microwaves weren't the best for even cooking and other criteria. It's not until about the mid 1980's that Radaranges start to pick up in ratings. Have not read everything, but it appears MCs with turntables out scored those without for even results.

Indeed Amana's "Radarange Plus RMC-30" micro/convection oven came in dead last after Sharp (top rated) and Panasonic.

CR also panned much of the "cooking" one was supposed to be able to do in a microwave oven. Cakes, meats, roasts, etc all sometimes were less than what one would expect, even when using browning devices and or coatings designed to give that effect.
 
As I recall, one could purchase spring-wound turntables for use in MW's without turntables. I had a small one for my mid-1980's 1 cu ft Amana (it was made by Hitachi). It cooked ok without the turntable, though - never noticed much of a difference with or without it.

The Kenmore Elite microwave I got around 1998 is fairly impressive in its attempts to even the cooking rays. There's a huge translucent amber plastic cover - about the size of a teacup saucer - with a visible rotating impeller, on the side of the cabinet where the magnetron lives. There is also a turntable. I like the impeller/magnetron cover because it's so easy to clean, and it provides some entertainment value as well.
 
I Remember Those Turn Tables

But as rarely used microwaves back then for more than reheating left overs,or heating water or milk never really bothered.

Again am going to wager that the reason so many of those huge work-horse microwaves from the 1980's and 1990's are still out there (by and large) in good shape is they never got much of a workout.

Housewives and whomever else tried to "cook" things in them probably reached the same conclusion as CR and moved on. For most things CR stated they got better results in their GE convection electric range/oven in the same or less time, and used less electric power than a microwave. The only exceptions would be things like baked potatoes and certain other foods.

Personally cannot imagine a meatloaf, roast beef or any other meat cooked by microwave alone. Convection/microwave yes, but not nuking by itself.

Oh for what it was worth both the Amana convection/micro and Panasonic did not fare well in CR's roasting tests. Both produced roast beef that was very rare in the center and over cooked every where else. This with the fact both ovens used temperature probes, while the Sharp didn't.

CR tested for even cooking same way as Whirlcool suggested; using slices of bread with a layer of cheese.

Strange thing: the first Amana Radarange Plus oven (with dial control) had three convection oven settings, low, medium and high. Low was really meant for using the oven as a dehydrator. Medium and high were for cooking. When the RMC-30 came out while the total watts for heating was increased, the oven temperature was set in all modes to about 300F in both convection only and combination. Both the Sharp and Panasonic could go up to 450F.

Am wondering if the "low" heating power was the reason for Amana's poor roasting results.
 

Similar threads

W
brand new Bosch Home Professional tumble dryer made weird knocking noises. What was the problem ?
2
Replies
52
Views
2K
Anatolian
A
Ultramatic
Appliances: The Future is Battery Powered
2 3
Replies
83
Views
1K
tolivac
T
T
NYT on Induction Cooking
2
Replies
35
Views
1K
vacerator
V
sudsysenior
Problems an FL presents to a short arthritic elder
Replies
19
Views
127
rapunzel
R
F
New Member, Antique Appliance Lover
Replies
17
Views
267
fridgenut
F

Latest posts

Back
Top