RE: [TCML] Off topic, but hoping....

["Ralph W5JGV" <sparks@xxxxxxxxxxxxxx>]

> A while back, I was repairing microwave ovens for a living, and
> to aid my endeavors in that, I constructed a small magnetron tester
> that I saw in a repair manual.

The tester in the diagram will indicate the DC anode current in amperes the
magnetron is drawing.  Unfortunately, a gassy magnetron may draw apparently
normal power, but fail to produce proper RF output.

A much better test is to see what the RF output actually is.  This is done
by absorbing the power using a known volume of water and measuring the
temperature rise.

Here is the procedure which I unabashedly swiped from the internet:

"Alan & Susie Canton, Professional Home & Building Inspection Consultant,
Fort Worth, Texas
817 - 572-3300
Amateur Radio Operator N5GKY & N5GKX

MICROWAVE OVEN POWER OUTPUT TESTING

Q: How can I tell if my microwave oven is heating properly? (Original
Question sent to me)

A: Without a major investment in test equipment, the following test method
is amazingly accurate for checking the wattage output: The temperature rise
in 63 seconds, of 1 liter of water, (times 39) = the wattage output of the
microwave oven.


Measure up exactly 1 liter of water in a microwaveable container (thick
glass measuring cups tend to absorb more heat resulting in a lower reading).
Let the container of water (preferably plastic) stand until the water
measures room temperature on an accurate thermometer. Remove the thermometer
and place the liter container of water in the microwave oven. Close the door
and activate the microwave oven on High for 63 seconds. Immediately (be
carefully) measure the temperature of the heated water. Subtract the water's
original room temperature reading from the higher "heated" temperature
reading. This will equal the temperature rise (Delta T). Now take the
temperature rise and multiply it times 39. This figure will be the
approximate output wattage of the oven. There should be a nameplate on the
oven {{ Wattage Output 900 }} for example. Don't confuse this with the input
power, which for 900 watts output will be about 1.5 KW input. Perform the
test several times for an average, but don't be surprised if the reading is
150 watts lower than the nameplate. Remember a microwave oven is a Radio
Frequency (RF)Transmitter commonly around 2450 MHz (microwave band).  This
high of a microwave radio frequency causes the molecules of water, meat,
etc. to vibrate and generate heat. The Magnetron RF Output Tube emissions
(power out) will decrease with age. Professional servicing should be
considered with reading consistently 400 watts below the oven's nameplate
output rating."

73,

Ralph  W5JGV - WD2XSH/7

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