Usual failure modes of magnetrons?

Greetings All,
I have a Sharp brand "Half Pint" 400 watt microwave oven my wife and I
bought new in 1986. The thing still works like new. I use it now in
my shop because we have bought more powerful microwave ovens over the
years to use in our house. We have bought more than one because the
magnetrons in the others failed. At least I think the magnetrons
failed because there was still really high voltage going to the
magnetrons and the other oven functions worked (timer, digital
display, etc.). So I was wondering why my old Sharp Half Pint oven
still works and how magnetrons failed.
Thanks,
Eric

 

Magnetrons are still vacuum tubes with heaters in them. They are
probably made in China and quality control is letting crap out the door.

Paul

 

How did you measure the "really high voltage going to the magnetron"???

 

Sorry, you are wrong. CE aka China Engineering aka Crap Enforcement
doesn`t let quality in, so there is no quality production :]



Saludos Wolfgang

 

Yes, that is true, in some cases. On the other hand, I buy GPS receiver
assemblies, complete with antenna, by the thousands from China and have
never had a bad one.

Paul

 

Good to hear, that not every product is controlled by Crap Enforcement






Saludos Wolfgang

 

"Paul Drahn"

** Magnetrons for Sharp microwave ovens made in China back in 1986 ????

That was the era when Japan and Taiwan were dominant.



..... Phil

 

"Jim Yanik"

** Must be some cases of loss of vacuum.

Affects lots of valves, big and small.



..... Phil

 

I've dissected a few microwave ovens to salvage
transformers and for fun.

I've found cracked magnets on a few magnetrons.

I don't know if a cracked magnet would cause the
failure of a magnetron, if that was the root cause
of the failures or if some other failure caused
the magnets to crack.

--Winston

 

wrote:

(...)

I wonder if a cracked magnet could cause low microwave
output?

Sounds like a chicken and egg problem.
Excessive power dissipation in the magnetron might
cause a magnet to crack. (Line transient perhaps?)
The cracked magnet would push the magnetron
away from cutoff, forcing it to dissipate more
power which heats the magnets, etc.

--Winston

 

The new planned obsolescence.