On Thu, 20 Jan 2011 21:50:04 -0800, isw wrote:

In article ,
David Nebenzahl wrote:

On 1/19/2011 12:55 PM mike spake thus:

PeterD wrote:

On Wed, 19 Jan 2011 05:55:03 -0800, "William Sommerwerck"
wrote:

Can you return the oven? You can use the argument that it's
not fit for its intended purpose. Which it isn't.

Nope, my inability to forecast the consequences is not the
fault of the seller.

If your description is correct, the oven is grossly misdesigned.
You do not implement variable power by turning the magenetron on
for 15 seconds, then letting it sit for a minute! I've /never/
seen a microwave oven that works that way. My home GE works fine,
as do all those I've seen where I've worked.

Huh? Virtually all the ones I've seen do just that: run a 10 to 15
second on/off time cycle. The magnetron is turned on with a relay,
so rapid cycling just begs to blow that relay.

It's worse than that. A triac can fix the relay issue. The problem
is the thermal time constant of the magnetron filament.

I guess I'm showing my ignorance here, as I don't know much about
magnetrons, but why can't you just let the filament burn while you cycle
the HV, like you'd do with any other ordinary tube? I mean, with other
tubes, it's OK to apply power to the heater without any anode voltage,
right?

Not sure about the ones used in uwave ovens, but with some magnetrons,
once they get going, the filament power has to be reduced (sometimes to
zero) because the filament is heated by the impact of accelerated
electrons banging into it.


Neat trick since the filament emitts teh electrons...