On Sat, 03 Dec 2016 16:11:12 -0500, micky
wrote:
In sci.electronics.repair, on Wed, 30 Nov 2016 23:25:52 -0800, Jeff
Liebermann wrote:
On Wed, 30 Nov 2016 18:57:51 -0500, "tom"
wrote:
Stick an old CD in the MW and you can see exactly when the RF power starts.
Good idea. Another way would be to cram a wad of paper between the
door and the oven, and use a microwave leakage detector to measure the
resultant leakage. It there's a slow rise in output, you'll see it on
the meter, which you won't see on the CD.
You can really do that? I did do that with Amana model 2, that had no
door latches, only springs. To check if the microwave detector was
working, and it was. And to check if the oven was leaking and it
wasn't.
Yep, although the choke joint does a good job of blocking RF even with
a gap. I just crammed a few layers of paper into the door of my
Panasonic Sensor 1300U microwave oven. For a leakage detector, I used
an MD-2000 detector.
https://www.google.com/search?tbm=isch&q=md-2000+microwave
and a Micronta (Radio Shock) 22-2001:
http://www.radiomuseum.org/r/radio_shac_micronta_microwave_leaka.html
With about 1/32" wad of paper, and with me shoving my weight against
the door hold it closed, I got about a 5mw/cm^2 indication. There was
also a cup of water inside the oven.
The first time I ran it, it too about 5 seconds for the power to level
off. Repeated tests took less, down to about 2 seconds. Note that
the Panasonic oven uses "inverter technology" which might have
different characteristics than a conventional microwave oven:
http://www.sears.com/articles/appliances/microwaves/what-is-inverter-technology.html
The Micronta 22-2001 meter isn't calibrated, but I assume that
mid-scale is 5mw/cm^2, which is considered the danger level. I had to
play with the orientation for maximum indication, but it read about
2/3 of way up the green part of the scale, and did not go into the
red. Timing was about the same as the MD-2000 at about 3-5 seconds to
reach full power.
The first time I did the wad of paper in the door test was many years
ago on a different microwave oven. The reading was much higher and
the door had a machanical latch. How much higher, I don't recall.
There are plenty of more modern leakage detectors available.
https://www.google.com/search?q=microwave+oven+leakage+meter&tbm=isch
I suspect I could get some RF to leak out of the oven by taking a
length of coaxial cable, strip off 1/4 wavelength (31.3mm) from both
ends, stuff one end in the oven, and measure whatever is re-radiated
from the other end.
BTW, Radio Shack stopped selling its cheap detector years ago. I
suppose it was sold by someone else but I haven't seen it.
No loss.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558