Do Magnatrons wear out?

yes, the emissions from the cathode of the megnetron do decrease with time, causing longer heat-up times.

amdx wrote in news:44701$4f445909$18ec6dd7$9204 @KNOLOGY.NET:

The vacuum in the tube might slowly fail, the cathode heater does slowly degrade, the wavegiude might become dirty, and because of that become less efficient Also the magnet surrounding the tube might lose some of its power. And lately china import sometimes is a bit wacky...

Yep. The thorium oxide coating on the cathode slowly "evaporates" away. Another cause is a sloppy filament winding which sometimes produces odd oscillations.

The rated life for consumer magnetrons is about 2000 hrs. If you live on 5 minute TV dinners, that's about 24,000 dinners.

You can check your microwave oven output with a simple calorimeter.

(see Pg 16). This isn't IEC 705-88 but is good enough. The instructions are not very clear as to how to make the measurement. You do NOT cook the thermometer. I made this mistake once. The end blew off, spraying the oven with broken glass.

Mumbo-jumbo on the topic:

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# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com               jeffl@cruzio.com
# http://www.LearnByDestroying.com               AE6KS

There's a simpler way. I've use the following method to test various microwave ovens:

First clean the microwave. (Food splatters drain power horribly.) Put a 12oz microwave-safe coffee mug, with 10oz of 72F water in it, in the microwave. Turn it on, full power, and time how long it takes for the water to start boiling. In my experience, for "typical" home microwaves it's about 4min 0sec. Powerful ovens boil water faster, cheap or damaged ones take longer. Certainly if it takes more than about 6min, it's either damaged or just crappy quality.

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Cheers,
Robbie Hatley
Santa Ana, CA, USA
lonewolf (at) well (dot) com
http://www.well.com/user/lonewolf/

This is a GE microwave manufactured 25 yrs ago. The next one will probably be a wacky Chinese Import. Mikek

"Jeff Liebermann"

** Hmmmmm....... 24,000 microwave dinners at the rate of one per day takes nearly 66 years to consume.

I wonder if the consumer of the microwave will die first ?

.... Phil

I just laid a Goldstar to rest that I purchased in 1987. The new one is just about 6 months old and already it sounds like it's on it's last legs.

Depends on how much lead is in it. :)

Yes. Anyone that consumes a microwave oven is likely to die.

I've sometimes speculated on what causes an oven magnetron to fail. Internal arcing will certainly shorten the lifetime of the device. Same with overheating from extended cooking time. However, my guess is some glass envelopes are badly sealed and fail from burning the cathode coating. I can't see the getter from the outside of the magnetron (without breaking the glass), but I suspect it is past its prime.

Another guess is that the glass is insufficiently baked to remove all the water and gasses dissolved into the glass.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

That's life. Replace the old one. You can purchase new Magnetrons.

Replacement magnetrons are usually priced between $60 and $120. New, low end, commodity microwave ovens average about $160. A repair might be worthwhile if the old oven is in good condition.

What I was doing for a while was salvaging old working microwave ovens for the electronics and magnetron. The theory was that I might run into the same model and could use the parts. In about 20 years, I've replaced exactly one magnetron from my pile, and it blew up in about a month. I recycled the pile a few years ago and currently use new parts.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Of course they wear out.. THey are a tube, they suffer from all the same problems.. On top of that, they are self oscillating and subjected to showing effects even sooner than a conventional tube working as hard.

Jamie

YES!!! Magnetrons like any type of tube will wear out with use. But, in a m= icrowave oven there are control circuits and the power supply that must als= o be verified.=20

I suggest to not work on your own microwave oven. Give it in for a service = estimate. There are high voltages and high current involved that are lethal= to mess with. A professional microwave oven tech will have the proper test= equipment, and service information to make a proper evaluation of the faul= t.=20

Jerry G.=20