From: John De Armond
Subject: Re: RV Microwave Question
Date: Sat, 26 Jan 2002 19:23:21 -0500
(Bill, I know you revel in ignorance of theory so ignore this post)
The tuning of the fork to get a resonant loop (necessary to get sufficient
voltage for an arc) is fairly critical. You can vary the tuning by either
trimming the tines or simply spreading them. A wavelength at 10.525 ghz (the
approximate operating frequency) is 2.85 cm so if the length around the loop
is kept to a multiple of that, the arcing will be at its best.
It WILL arc. I have a little show that I put on for visitors to my shop that
I call "fun with microwaves". Making a fork arc is one of the tricks. Here's
That's a 1.25 liter glass bulb filled with neon gas and excited by a microwave
oven magnetron operating in free air.
Jim Walker wrote:
> All I can say is that I did get some arcing from a fork when I tried it.
> There was nothing of the kind from a spoon. If your microwave doesn't show
> arcing with a fork, then you should at least see some heating of the tines.
> On the other hand, a spoon will remain cool.
> Jim Walker
> Northern Virginia
> > Ok, I overcame my hesitancy. I put a fork in there with nothing else. No
> > fireworks.
> > --
> > bill
> > Theory don't mean squat if it don't work.
From: John De Armond
Subject: Re: Samsung microwave recall
Date: Mon, 17 Nov 2003 21:04:34 -0500
On 17 Nov 2003 17:05:16 -0800, email@example.com (Ellen) wrote:
>Samsung has issued a recall for some of their microwaves built between
>May 2000 and September, 2003. The ovens turn themselves on and of
>course can overheat and possibly cause a fire. Our microwave started
>up twice before we unplugged it. I hate to think what could have
>happened if this occurred when we were away and our dog was in the RV.
Well, if your dog can operate the microwave, he may have had his first hot
meal in awhile. Otherwise nothing that much matters.
The unit would run until the thermal cutout switch on the magnetron assembly
opens and shuts down the unit. Assuming they use a switch and not a thermal
fuse, the oven will turn back on when it cools off. The controller will have
been reset so it won't start heating until commanded to again.
I torture test microwaves in my restaurant. I perform phase 1 of baking our
potatoes in the microwaves. Phase 2, taking about 15 minutes, is done on the
steam table which finishes the tater and makes it taste like it was baked for
an hour in a regular oven. Anywho, it is not unusual for the bank of ovens to
be turned on in the AM and not turned off all day, baking taters as fast as
possible. I've equipped the ovens with extra cooling fans to help them run
Usually the first failure is the digital control. I rip it all out and
replace it with a spring wound timer. Once this is done the microwave runs
whenever the timer is set and the door is closed. it is not unusual for
employees to remove taters and leave the timer set, turning the oven back on
while empty. Modern ovens can handle this without damage. It gets hot, turns
off, cools and turns back on. With the mechanical timer, if any time remains,
the process repeats. This is what happens without the extra fans. With the
extra fans, the thing usually runs until the timer runs out.
If your microwave is built-in, it will overheat and turn off very fast. I
tried to use the Panasonic built into my Mom's motorhome to help bake potatoes
at a concession event. It overheated and tripped after only about 15 minutes.
Not enough air flow using the factory supplied build-in kit. Some extra fans
to vent the enclosed spaces solved that problem.
hey, until you get your replacement unit, you can have some fun with it. Just
put those AOHell CDs you're always getting into the oven. Then, next time the
oven turns on, it'll give your dog a nice fireworks show!
From: John De Armond
Subject: Re: Ghostly microwave
Date: Thu, 11 Nov 2004 02:23:51 -0500
On Wed, 10 Nov 2004 06:52:10 GMT, firstname.lastname@example.org wrote:
>Twice in the past week our Sharp microwave exhaust vent started up by
>itself, not while the unit was in use. Tapping the appropriate control
>switch had no effect whatsoever, it could not be turned off in the
Is this an over-the-stove microwave with a built-in range hood? Is the
fan switch part of the microwave control panel? It is a real switch or
just a touch key on the panel.
>The first time it happened I tripped the dedicated AC breaker and the
>vent stopped, but the last time I tripped the breaker and it still
>kept running. Tried turning off the main breakers but no joy, and
>finally had to unplug the microwave in order to turn it off.
If you really did hit the right breaker(s), this sounds like a wiring
problem of some sort. By "main breaker" do you mean the electrical
panel's main breaker that would kill the whole RV? If power is getting
around that main breaker somehow, there's a problem.
>Anyone got any ideas how to snuff the gremlin that's running around
>inside there somewhere? New microwaves are not that expensive, so it
>probably would make more sense to buy one rather than call a
>high-priced repairman, but then I'm faced with finding one to exactly
>fit the existing cabinetry.
Until I get answers to the above questions, I don't have any suggestions.
However I can offer some experience.
I've bought literally several dozen ovens for my restaurant and
concessions operation. I've found that the electronic controls are VERY
sensitive to power quality, much more so than other appliances or even
computers. They generally don't like generator power, particularly when
the generator is stopping or starting. I've analyzed several different
control boards. Without getting technical, the cheap-sh*t board design
relies on good clean 60 hz sine wave electricity for proper function.
I got tired of fighting the problems so on the ovens that are likely to
run on generator power, I remove the electronics and install a simple
spring-wound timer. Problem solved. Too bad they don't make a high
powered microwave with a mechanical timer anymore.
Point I'm making is, if your microwave is operating on generator power or
if there is inverter power reaching it then it is probably having a
problem with the power and the microprocessor onboard is acting up.
Anything in the rig that generates a significant amount of EMI can also
probably cause a problem. Something like a high powered solid state
About the unattended turn-on problem with Sharp ovens that spurred the
recall. When that hit the news I checked into the details of the problem,
as most of mine are Sharp brand. Before investigating, my first thought
was "here we go with another unintended acceleration" panic again. Turns
out the problem was real but probably is unrelated to your problem.
The problem was that the touch pad keyboard was of inferior quality. The
little dome spring inside the button would weaken or crack and sometimes
make contact from vibration or whatever. Normally not a problem because
it takes several different keystrokes to turn on the oven. With one
exception. The "add a minute" button. A single operation of this button
would put a minute on the timer and turn the oven on. A weak spring
responding to vibration could rack up many minutes on the timer.
I've noticed on the last couple of Sharp microwaves I've purchased in the
last year that they've changed things a little. The "add a minute" button
still adds a minute but it doesn't start the oven. The START key has to
be pressed. Sad homage paid to the blood sucking lawyers, I'm afraid.
Too bad. I really liked the original function.
Before someone asks what I do with so many ovens, I bake massive
quantities of baked potatoes. Here's a process I developed that makes
baked potatoes that taste just like they've been in the oven for a couple
Put one or two 50-count (1 lb) potatoes in the 1100 watt or higher oven
and cook for 9 minutes per potato. Then place the potato on a steam table
(moist 212 deg heat) and leave it for 15 minutes or so to allow the
starches to fully convert. At home, wrapping the spud in foil and putting
it in a 250 deg oven does about the same thing. Potatoes processed this
way are just as fluffy and sweet as when baked for hours in a conventional
oven. The spud will stay fresh on the steam table for up to an hour.
I have 3 wheeled carts set up with 6 ovens per cart. I roll these carts
out to catering event, connect each one to a generator and start mass
production of spuds. I can crank out 36 spuds every 18 minutes with this
setup and they all taste like they just came out of an oven.
Customers are so funny. Had a lady come in about a year ago and tell a
waitress that she wanted one of our delicious genuine baked potatoes, that
she really hated those microwaved potatoes other restaurants serve. I
just grinned and gave her what she wanted :-)
From: John De Armond
Subject: Re: Ping Neon John
Date: Wed, 19 Sep 2007 00:45:59 -0400
>-> Hey John,
>-> I've got a Panasonic microwave that popped the internal 18A fuse last
>-> night; went troubleshooting this AM w/a new 20A fuse and the first thing I
>-> noticed on this little jewel, rated 120V 12A, is that it is drawing
>-> 1950-2000 watts per my KAW!
>-> Any ideas other than saving a few parts and buying a new one?
My experience in fixing a BUNCH of microwaves is that the voltage doubler capacitor
is usually the first thing to blow, followed by the doubler diode. Yours sounds like
a bad cap. Is it making any heat?
Those caps are fairly expensive (~$25 range) but all microwaves use one of about 3
values so if you can find an old one to rob or maybe a used appliance store that has
one in the boneyard, you can fix it. Otherwise a new microwave is probably the
Save the goodies. You can do neat stuff like this:
That's me holding a neon-filled globe near the antenna of a 600 watt magnetron. The
camera doesn't do the brightness of that globe justice!
I've been wanting to build a sulfur lamp. This lamp uses a microwave oven magnetron
to drive a small quartz globe filled with argon and elemental sulfur. It is one of
the brightest and most efficient light sources going. I just need to source a quartz
globe of the proper diameter. I can fill and evacuate it here.
A bare magnetron makes an excellent hand warmer. That's what I use the one in the
photo for (after mounting it in a box with a fan). Just hold your hands out at arm's
length about 6-8" away.
The bare radiator is eye-safe at arm's length (yeah I have a microwave survey meter
and have measured) but one would need to be careful if any sort of reflector or other
wave guide were in the vicinity.
I have another little gadget that I've been playing with off and on for awhile. 4
magnetrons feeding a large feedhorn. A very effective tool to shut down loud
stereos..... :-) A microwave oven is a delightful electronic warfare tool :-)