Potential Problem With Older Microwaves

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Robert, how does your grand dad's Brother microwave manage to brown food? Does it have a convection or broil-type heating element, in addition to the microwave?

When we someday replace our over-the-range microwave, I'm thinking it would be handy to have a microwave that also has a built-in convection baking/roasting feature.
 
non-microwave heat modes

i have seen a few microwave ovens with a calrod element around the top of the oven
chamber-i have a 1985 litton with this.Haven't seen a microwave oven with fan-
forced"convection"resistance heating mode, but there might be some...
 
Fan Forced Convection

Since one is on the hunt for a vintage Micro/Convec oven have been pouring lots of part diagrams. So far the Thailand made Whirlpool (that Gansky had a NIB model, given to Mixfinder) is the first I've found there the heating element surrounded the rear fan for "true convection".

Every other vintage model one has looked over have just the one element in the top "roof" (Amana Radarange, Panasonic Dimension 3, and 4, for instance), others such as the Sayno built Sears Micro/Convection oven have two conceled elements, one top and the other bottom. For the later Sears had two models, the early version where the fan was located on top and blew down had two heating elements, while the later model moved the fan to the rear as well as the heater, but cannot tell if it surrounds the fan or is just built into the wall.

All microwave/convection ovens that *claim* to broil have at least the one element conceled in the top. This IMHO means the the broiling probably leaves much to be desired since the whole purpose of the process is to place food under radiant heat. The fact that the heat is now behind a metal wall of varying thickness must complicate things.

According to the cook book I have for the Panasonic "Dimension 4", broiling a steak or chops takes on average 15 minutes or so for both sides. My little vintage Toastmaster "flip" oven/broiler with the two exposed heating rods can do it at about 7min to 10min depending how you like them done.

L.
 
I have a GE "Advantium" microwave-type oven that uses Halogen lamps as the heating elements for baking or browning,broiling.works very well and FAST.The halogen elements are on the top and bottom of the oven.
 
I have drug home dozens upon dozens of Radaranges, 95% pre 1981. Out of all of those I can think of only 1 that had a noticeable deficiency in power due to a worn magenetron. The majority needed nothing but a clean up, others a going-through of the touch-panel power supply section. Vegas can't touch those odds.

Good Radaranges can be had for much less than $100 locally; usually 20 bucks is the going rate. At those dollars rolling the dice isn't so bad. -Cory
 
Hey, why stop at microwave/true convection/true broil?

Why not a refrigeration mode, as well as the capability to shine your shoes?

Just kidding... but the more a product tries to cram in essentially opposite tasks, I think the more expensive and prone to failure it probably will be, as well as being mediocre in one or more of the designed in tasks.

But hey, if it keeps you young, go for it!
 
*LOL*@ Sudsmaster

While cannot fathom broiling in a microwave, there are those whom report excellent results with vintage and modern versions of such ovens like the Sharp model.

What I've found by pouring over owner's manuals for both modern and vintage combo micro/convection/broil ovens is the amount of time one must pre-heat the oven for functions involving heat (broiling and or convection).

To broil and or bake in convection in some older and new models you have to pre-heat for anywhere from 8, 9, 10 or more minutes. Add this to the longer broil times because the heat is indirect (hidden behind the walls of the oven) and that is allot of power wasted IMHO.

My Toastmaster broiler/oven pre-heats for broiling in about two minutes.
 
Well, I get by just fine with separate appliances for different functions.

GE P-7 electric (non-convection) 24" wall oven for standard baking. Works fine.

Cuisinart convection toaster oven that I use primarily to cook 12" De Giourno Supreme pizzas. Works great for that. Preheats in 5 min or less.

Two microwaves used to thaw items, heat up frozen entrees etc, reheat leftovers, popcorn, etc. Nothing fancy, but basically what these things do best. I have in the past tried using microwaves for more complex cooking (roast chicken, baked potatoes for example) but the results have never been all that great.

For grilling/broiling/rotisserie, have a propane gas grill out on the covered patio that does all that just fine without filling the house with smoke, fumes, or grease spatter. Works great grilling steaks, and also for rotisserie cooking of poultry (chicken, turkey).

For slow cooking, a Hamilton Beach 6 qt unit with temp probe. This thing works great for slow-cooked pork shoulder.

For traditional roasting, a smoker with offset firebox. Good for ribs.

For traditional coal-fired BBQ, a Kingsford "Egg" covered charcoal grill. It makes a mean smoked turkey too, but it's rather labor intensive.

Oh, yeah, I have had a few electric portable grills, George Foreman type clones, and even an electric rotisserie ("Baby George"). These work ok but the results are sort of bland and they spend most of their time in deep storage. I frankly prefer using a good frying pan for making burgers, fish, etc, and steaks in winter when I don't feel like firing up the gas grill. So easy just to pour off unwanted grease/oil if that's what you want. And in fact a good frying pan, a 3 qt covered saucepan, and a reliable gas burner or two, are all one really needs for basic but healthy cooking. I love all the gadgets as much as anyone else (and my kitchen is overloaded with them), but when it comes right down to it, those are the items one can always fall back on.
 
I have the sneaking suspension that Ms. Launderess does not have the room, space or storage for so many differnt (single use) appliances! I'm guessing that's why she wants a multi-purpose tool like the combo unit....
 
Laundress, are you sure you've got the hang of the Panasonic Dimension 4 Combi's?

The one's we've always had going back as far as 1980 have had the grill element in the top which is exposed (or behind a grill), plus a hidden element with the fan for convection. The Grill element is only on when Grilling, there is a seperate element/fan for combi cooking.

The 2kw element in the Aussie ones will preheat to 180degC in about about 10 mins or so.

In Australia toaster oven's arent popular, so its a great way to get a small oven that heats up fast and combines the best of both worlds into one product.
 
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."

 
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.
 

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