Microwave oven
 

It appears that our microwave oven has lost cooking/heating power over the
years. Is that possible: Can the magnetron put out less power as it ages?
How can one test the heating power of a microwave oven: Perhaps by heating
a known quantity of water to a desired rise in temperature over a prescribed
time period? Are there any such measures for a microwave oven of a known
original/rated power?

Rick

Microwave oven
 

On Sun, 19 Oct 2008 02:22:41 GMT, "Richard G. Gould"
put finger to keyboard and composed:

It appears that our microwave oven has lost cooking/heating power over the
years. Is that possible: Can the magnetron put out less power as it ages?
How can one test the heating power of a microwave oven: Perhaps by heating
a known quantity of water to a desired rise in temperature over a prescribed
time period? Are there any such measures for a microwave oven of a known
original/rated power?

Rick

Notes on the Troubleshooting and Repair of Microwave Ovens

7.1) Testing the oven - the water heating test:
http://www.repairfaq.org/REPAIR/F_mi...tml#MICFAQ_017

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Microwave oven
 

It appears that our microwave oven has lost cooking/heating power over
the
years. Is that possible: Can the magnetron put out less power as it ages?
How can one test the heating power of a microwave oven: Perhaps by
heating
a known quantity of water to a desired rise in temperature over a
prescribed
time period? Are there any such measures for a microwave oven of a known
original/rated power?

It's not a magnetron, it's a klystron. It's a tube and tubes get weak.
But more likely, one of the power sources has become weak.

I don't know where you get your information, but microwave ovens use
magentrons. A klystron is a rather different sort of microwave device. For
one thing, it's an amplifier, not an oscillator (unless you misalign it,
especially the B cavity).

I know about these things, because I used to install and align klystrons. I
could tell you a few "Jedi tricks".

Microwave oven
 

William Sommerwerck wrote:
It appears that our microwave oven has lost cooking/heating power over
the
years. Is that possible: Can the magnetron put out less power as it ages?
How can one test the heating power of a microwave oven: Perhaps by
heating
a known quantity of water to a desired rise in temperature over a
prescribed
time period? Are there any such measures for a microwave oven of a known
original/rated power?

It's not a magnetron, it's a klystron. It's a tube and tubes get weak.
But more likely, one of the power sources has become weak.

I don't know where you get your information, but microwave ovens use
magentrons. A klystron is a rather different sort of microwave device. For
one thing, it's an amplifier, not an oscillator (unless you misalign it,
especially the B cavity).

I know about these things, because I used to install and align klystrons. I
could tell you a few "Jedi tricks".



.....Just remembering a few years of tweaking 1kw klys'es at 0-dark-30 in
the military and watching the beam current like a hawk.....


ISTR some commercial process heating chambers that used multiple
klystrons for outputs.

Microwave oven
 

In article , "William Sommerwerck" wrote:
It appears that our microwave oven has lost cooking/heating power over
the
years. Is that possible: Can the magnetron put out less power as it ages?
How can one test the heating power of a microwave oven: Perhaps by
heating
a known quantity of water to a desired rise in temperature over a
prescribed
time period? Are there any such measures for a microwave oven of a known
original/rated power?

It's not a magnetron, it's a klystron. It's a tube and tubes get weak.
But more likely, one of the power sources has become weak.

I don't know where you get your information, but microwave ovens use
magentrons. A klystron is a rather different sort of microwave device. For
one thing, it's an amplifier, not an oscillator (unless you misalign it,
especially the B cavity).

I know about these things, because I used to install and align klystrons. I
could tell you a few "Jedi tricks".


I suppose they still use Klystrons as deep space power amplifiers such as in Apollo missions.
I think the standard power was 20 KW and made by Collins. A Hydrogen Maser
was also used as a low noise amplifier and was used as the primary frequency
standard, Cesium second. I just updated my learning from the web. A Cesium
standard is basically a Xtal oscillator buffered with a atomic feedback loop and
has poor short term stability. The Maser has the best short term stability and porr long term.

greg

Microwave oven
 

GregS wrote:

I suppose they still use Klystrons as deep space power amplifiers such as in Apollo missions.
I think the standard power was 20 KW and made by Collins. A Hydrogen Maser
was also used as a low noise amplifier and was used as the primary frequency
standard, Cesium second. I just updated my learning from the web. A Cesium
standard is basically a Xtal oscillator buffered with a atomic feedback loop and
has poor short term stability. The Maser has the best short term stability and porr long term.

greg


Klystrons & Klystrodes were common in UHF aTV transmitters. The last
I used were a set of 65 kW, made by EEV on us Ch. 55. They are being
replaced by solids state transmitters.


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Microwave oven
 

I suppose they still use klystrons as deep-space power amplifiers
such as in Apollo missions.

The Apollo mission was not "deep space". Nevertheless, I installed several
Varian klystrons in NASA's STDN.

Microwave oven
 

In article , "William Sommerwerck" wrote:
I suppose they still use klystrons as deep-space power amplifiers
such as in Apollo missions.

The Apollo mission was not "deep space". Nevertheless, I installed several
Varian klystrons in NASA's STDN.

Well the moon was a bit farther away. I don't remember what things
were tracked by the maser. Maybe it was just a backup, but easily overloaded
on strong signals. All the 3 main 85 foot MSFN/STDN stations had masers.
After Apollo, ERTS or Landsat was the main preoccupation. Tracking the
Alsep packages on the moon was also done for a VLBI experiment.
After that the stations were also recording Helios orbiting the Sun, a
very week signal. You really had to play with it to get phase lock.

Here is a link to the NASA bible for the stations. Its a big file....
http://zekfrivolous.com/nasa/NASA-SP-87.pdf

greg

Microwave oven
 

"Richard G. Gould" wrote in message
...
It appears that our microwave oven has lost cooking/heating power over the
years. Is that possible: Can the magnetron put out less power as it
ages? How can one test the heating power of a microwave oven: Perhaps by
heating a known quantity of water to a desired rise in temperature over a
prescribed time period? Are there any such measures for a microwave oven
of a known original/rated power?

Rick


The waveguide on the output of the mag (and it is a mag - ignore what
clodhopper says below about it being a klystron) can become coated with
resolidified vapourised grease and clag from the food that's been cooked in
it - especially if it is a combination type that has a conventional oven in
it as well. This can result in substantially reduced microwave cooking
efficiency.

Arfa

Microwave oven
 

Arfa Daily wrote:
"Richard G. Gould" wrote in message
...
It appears that our microwave oven has lost cooking/heating power over the
years. Is that possible: Can the magnetron put out less power as it
ages? How can one test the heating power of a microwave oven: Perhaps by
heating a known quantity of water to a desired rise in temperature over a
prescribed time period? Are there any such measures for a microwave oven
of a known original/rated power?

Rick


The waveguide on the output of the mag (and it is a mag - ignore what
clodhopper says below about it being a klystron) can become coated with
resolidified vapourised grease and clag from the food that's been cooked in
it - especially if it is a combination type that has a conventional oven in
it as well. This can result in substantially reduced microwave cooking
efficiency.

Absobloominglutely

The first thing to do with an oven which appears to have lost
perfomance, is to give the cavity a good clean, including the inside
glass of the door and the waveguide cover and to check that there`s no
nasty carbonised gunk up the waveguide. Simply replacing the waveguide
cover perks them up a bit.

It`s also important to check the spade connectors on the magnetron,
these sometimes become loose and erode away making intermittent contact
for the heater current. My own Panasonic was suffering from this - about
one in four cookings would fail, replacing the spade connectors cured
the problem.

It is possible (IME) for magnetrons to lose power over time, sometimes
the antenna cap gets eroded away and sometimes you find cracks in one of
the magnets.

Ron

Microwave oven
 

Ron Johnson wrote:

It is possible (IME) for magnetrons to lose power over time, sometimes
the antenna cap gets eroded away and sometimes you find cracks in one
of the magnets.

Ron

Yes they do loose power over time ! It depends upon how fast the
filament/cathode looses the ability to produce electrons. Often
Thoriated Tungsten is used in the heater ! If it gets hammered it
rapidly looses emission.

--
Best Regards:
Baron.