UNIVERSITY PARK, Pa. -- We all know when age is creeping up on us -- joints creak, hair goes gray, wrinkles appear. But how do you know when your microwave oven is nearing retirement age? A food scientist in Penn State's College of Agricultural Sciences offers a few tell-tale signs of appliance decline.
"Microwave ovens of any price easily should last 10 years or more," says Swamy Anantheswaran, associate professor of food science. "But there will be changes in performance -- usually a decline in power so gradual that consumers never notice it."
The Magnetron
Anantheswaran explains that the magnetron, the electrical element that converts electrical energy into microwave energy, will not maintain the same power levels over time. "If a new microwave oven boils a cup of water in one minute, after five or 10 years it may take 90 seconds," Anantheswaran says.
Although microwave ovens lose power as they age, Anantheswaran says most consumers unconsciously adjust cooking times without realizing the oven is not performing as efficiently.
"You can replace the magnetron in a microwave oven," Anantheswaran says. "But I don't recommend it. It would probably be cheaper to buy a new microwave oven."
Anantheswaran says magnetrons can interfere with cellular phone transmissions because both products emit microwaves within the same frequency range.
"The cellular phone industry would like magnetrons to confine their energy emission to a more specific frequency to prevent interference or noise leakage onto phone calls," he says. "If the microwave oven manufacturers have to develop more frequency-specific magnetrons, the price of microwave ovens will go up."
The Power Fuse
All microwave ovens are outfitted with a power fuse designed to cut power to the oven if circuits overload. Anantheswaran says ovens can overheat and blow the power fuse. "If the oven is used to cook foods with very little moisture, the heat can build up in the oven cavity and overheat the circuits," he explains. "If you're cooking a dry material, such as popcorn, give the oven a break before popping another bag."
A blown power fuse can be repaired for $10 to $20, but Anantheswaran says consumers should not try to repair a microwave oven themselves. "These appliances are not meant to be serviced at home," he says. "The problem may be something other than a fuse."
Gasket Leakage
Anantheswaran says microwave ovens can leak microwave radiation if the gaskets around the door and other parts of the oven become worn or pitted.
"Several companies make products that can measure whether microwaves are leaking from an oven," Anantheswaran says. "These products, some of which are business card-sized flat cards, will change color if microwaves are leaking."
Anantheswaran says consumers should consult an appliance repair shop to replace a worn gasket.
"Many microwave oven parts become scarce after a few years," he says. "It's unlikely you'll be able to easily find a gasket for an older oven. Get an expert opinion from the technician to see if it's time to buy a new one."
Carousels
Anantheswaran says rotating carousels can jam, particularly when rectangular casserole dishes are too large to be turned by the carousel. "Most glass platforms are shaped like a shallow bowl," he says. "In some ovens you can flip the glass platform over, allowing the carousel mechanism to rotate freely beneath the glass. The casserole dish won't turn, but the heating will be the same."
Anantheswaran, who has used the same microwave oven in his home for the past 12 years, says homeowners should feel no rush to replace older ovens if they need a minor repair. "If you are used to the way your car runs, why replace it?" he says. "It gets you where you want to go."
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EDITORS: For more information, contact Swamy Anantheswaran at 814-865-3004.
Contacts: John Wall jtw3@psu.edu 814-863-2719 814-865-1068 fax