Do Magnatrons wear out?

amdx

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Feb 21, 2012, 9:48:19 PM2/21/12

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I have small microwave and it seems the power is getting less and less
as time passes. Do Magnatrons wear out?
Mikek

Sjouke Burry

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Feb 21, 2012, 10:12:21 PM2/21/12

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amdx <am...@knologynotthis.net> wrote in news:44701$4f445909$18ec6dd7$9204
@KNOLOGY.NET:

> I have small microwave and it seems the power is getting less and less
> as time passes. Do Magnatrons wear out?
> Mikek
>

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...

hrho...@att.net

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Feb 21, 2012, 10:11:21 PM2/21/12

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

Jeff Liebermann

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Feb 21, 2012, 11:08:42 PM2/21/12

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On Tue, 21 Feb 2012 20:48:19 -0600, amdx <am...@knologynotthis.net>
wrote:

>I have small microwave and it seems the power is getting less and less
>as time passes. Do Magnatrons wear out?
> Mikek

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.
<http://www.gallawa.com/microtech/output.html>
<http://www.zyra.info/micropwr.htm>
<http://www.eletrodomesticosforum.com/es/cursos/horno_microondas/Inverter.pdf>
(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:
<http://www.ehow.com/info_12020972_microwave-ovens-lose-power-time.html>

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

Robbie Hatley

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Feb 22, 2012, 3:49:36 AM2/22/12

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On 2012-02-21 8:08 PM, Jeff Liebermann wrote:

> You can check your microwave oven output with a simple calorimeter.
> <http://www.gallawa.com/microtech/output.html>
> <http://www.zyra.info/micropwr.htm>
> <http://www.eletrodomesticosforum.com/es/cursos/horno_microondas/Inverter.pdf>

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.

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

amdx

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Feb 22, 2012, 7:35:10 AM2/22/12

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

Phil Allison

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Feb 22, 2012, 8:07:37 AM2/22/12

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"Jeff Liebermann"

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

** 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

JW

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Feb 22, 2012, 9:01:08 AM2/22/12

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On Wed, 22 Feb 2012 06:35:10 -0600 amdx <am...@knologynotthis.net> wrote in
Message id: <e0373$4f44e0b8$18ec6dd7$32...@KNOLOGY.NET>:

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.

JW

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Feb 22, 2012, 9:02:12 AM2/22/12

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On Thu, 23 Feb 2012 00:07:37 +1100 "Phil Allison" <phi...@tpg.com.au>
wrote in Message id: <9qk7l4...@mid.individual.net>:

Depends on how much lead is in it. :)

Jeff Liebermann

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Feb 22, 2012, 12:32:31 PM2/22/12

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On Thu, 23 Feb 2012 00:07:37 +1100, "Phil Allison" <phi...@tpg.com.au>
wrote:

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.
<http://www.google.com/patents/US4132921>
Another guess is that the glass is insufficiently baked to remove all
the water and gasses dissolved into the glass.

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

amdx

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Feb 22, 2012, 12:47:16 PM2/22/12

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I figured 10 minutes a day, 365 days x 25 yrs = 1500 hours.
If I'm lucky the next one might out live me.
(Or that could be unlucky?)
Mikek

bw

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Feb 22, 2012, 2:17:31 PM2/22/12

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"amdx" <am...@knology.net> wrote in message
news:91cad$4f4529db$4b4c116f$20...@KNOLOGY.NET...

That's life. Replace the old one. You can purchase new Magnetrons.
http://www.ebay.com/sch/i.html?_nkw=magnetron&_sacat=43566&_odkw=&_osacat=43566&_trksid=p3286.c0.m270.l1313

amdx

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Feb 22, 2012, 2:33:50 PM2/22/12

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Naw, I can buy a new microwave to replace the old one for $40.
Mikek

Jeff Liebermann

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Feb 22, 2012, 2:47:52 PM2/22/12

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On Wed, 22 Feb 2012 13:17:31 -0600, "bw" <bwe...@hotmail.com> wrote:

>That's life. Replace the old one. You can purchase new Magnetrons.
>http://www.ebay.com/sch/i.html?_nkw=magnetron&_sacat=43566&_odkw=&_osacat=43566&_trksid=p3286.c0.m270.l1313

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.

Jamie

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Feb 22, 2012, 6:41:07 PM2/22/12

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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

Jerry G.

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Apr 2, 2012, 11:51:39 PM4/2/12

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YES!!! Magnetrons like any type of tube will wear out with use. But, in a microwave oven there are control circuits and the power supply that must also be verified.

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 fault.

Jerry G.