Hi have this 15 year old Amana microwave that, as of late, appears to
run its magnetron continuously for the entire cook time. Where should
I begin looking? How is the cycling of the magnetron controlled?

I found this in the FAQ:

6.22) Oven heats on high setting regardless of power setting


Power levels in a microwave oven are controlled by cycling the
microwave
generator on and off with a variable duty cycle - kind of like slow
pulse
width modulation. For 'HIGH', it runs continuously; for low, it may
run
10% on and 90% off; other settings are in between.

When the oven always seems to be stuck at high power, it is likely to
be
due to one of two possible causes - a faulty relay or Triac, or
controller.
The relay or triac may have failed in the on state. This will probably
show up with ohmmeter tests (with the oven unplugged!) but not always.

Replacements should be readily available. If the problem is is the
controller, it will be more difficult to diagnose as schematics for the
controller are usually not readily available. However, it could be
something
simple like a bad connection or dirty connector.

*******

I was assuming that under normal mode (high?), the microwave cycles,
but apparently, it runs continuously. The problem I am having is that
I used to be able to heat a cup of water to near boil in about 3
minutes. Now when I heat 3 minutes, the water is boiling furiously.
Either the normal mode was doing some cycling and now it is not or the
magnetron is now putting out more energy (is this likely?).

wrote:
Hi have this 15 year old Amana microwave that, as of late, appears to
run its magnetron continuously for the entire cook time. Where should
I begin looking? How is the cycling of the magnetron controlled?

Hi,

No model# posted....but most microwaves use a relay to cycle the power
off and on for the different cooking powers.
Some older units use a triac switch controlled by the board to cycle
the power levels.

jeff.
Appliance Repair Aid
http://www.applianceaid.com/

On 5 May 2006 06:11:11 -0700, wrote:

*******

I was assuming that under normal mode (high?), the microwave cycles,

I don't think so.

but apparently, it runs continuously. The problem I am having is that
I used to be able to heat a cup of water to near boil in about 3
minutes. Now when I heat 3 minutes, the water is boiling furiously.

So how could 100% of the time be hotter than it was before, and the
problem be the cycling?

I know they are different, but I"m sure a cup of water in my
microwave would also be boiling furiously at 3 minutes. This simple
test of yours seems like a good one, but given the confusing result,
it doesn't seem sufficient.

If you want to know when the microwaves are running, put a radio next
to it set to a weak AM station. (Or perhaps a strong AM station but
tuned off-frequency (haven't tried that.))

When you get more static, the magnetron is on.

You can also test other than full power this way. Any power less than
full power will cycle and you can tell by the static in the radio.

Either the normal mode was doing some cycling and now it is not or the
magnetron is now putting out more energy (is this likely?).

That's a neat trick with the AM radio. I wonder if I still own one...

The wife reported that she usually heats her water up to 1.5 minutes
and that lately it seems to get alot hotter. This is at "high," that
is why I asked if there was cycling on high, then a no cycle condition
(stuck relay) would explain it. If there is normally no cycling on
high, which I guess is how these things are made, the only explanation
could be that the magnetron is putting out more energy than before, is
this possible? I have had problems in the past with blown fuses, but
replacing them gets the unit working again. Also, some mugs seem to
get real hot, which I am guessing translates in hotter water given the
same cook time.

The unit is actually GE, not Amana Model JE2800 001 made on July 1988.

On 6 May 2006 10:25:16 -0700, wrote:

That's a neat trick with the AM radio. I wonder if I still own one...

How could you listen to AM stations without an AM radio?

The wife reported that she usually heats her water up to 1.5 minutes
and that lately it seems to get alot hotter. This is at "high," that
is why I asked if there was cycling on high, then a no cycle condition
(stuck relay) would explain it. If there is normally no cycling on
high, which I guess is how these things are made, the only explanation
could be that the magnetron is putting out more energy than before, is
this possible?

Maybe. You should contact the Department of Energy. They may be able
to make more of these devices and help solve the energy shortage.

You never said if you can use other power levels to get less power.
If I were you I would find a factor by which either to reduce the time
or reduce the power level, and run with that until the whole thing
fails.

I have had problems in the past with blown fuses, but
replacing them gets the unit working again. Also, some mugs seem to
get real hot, which I am guessing translates in hotter water given the
same cook time.