Usual failure modes of magnetrons?

[[email protected]]

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

 

[Paul Drahn]

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

 

[mike]

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

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

 

[Wolfgang Allinger]

Magnetrons are still vacuum tubes with heaters in them.

They are probably made in China and quality control is letting crap out
the door.

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



Saludos Wolfgang

 

[Paul Drahn]

Magnetrons are still vacuum tubes with heaters in them.

They are probably made in China and quality control is letting crap out
the door.

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

 

[Wolfgang Allinger]

They are probably made in China and quality control is letting crap
out the door.

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

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.

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






Saludos Wolfgang

 

[Phil Allison]

"Paul Drahn"

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

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

That was the era when Japan and Taiwan were dominant.



..... Phil

 

[Phil Allison]

"Jim Yanik"

usually,the MW output drops,perhaps from reduced cathode emission.
or the filament opens,they don't last forever.
or internal arcing causes the PS fuse to blow.

Not much else to go wrong.

** Must be some cases of loss of vacuum.

Affects lots of valves, big and small.



..... Phil

 

[Winston]

"Jim Yanik"


** Must be some cases of loss of vacuum.

Affects lots of valves, big and small.

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

 

[Winston]

[email protected] wrote:

(...)

Every one I have ever salvaged had low magnetron output or a bad HV
transformer. Never seen a cracked magnet. But those old magnets are
great for fooling around with as they ar so strong.

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

 

[josephkk]

Like you we have a small Goldstar oven that we got as an incentive for
visiting a time share back around 1985. The thing has a simple wind up
clock timer that rings a bell when it runs down. It too has worked
flawlessly all these years. I've been repairing consumer electronics
all my life and although I've never heard the term before I firmly
believe that "crap engineering" is in everything today and is
definitely alive and well in China. Lenny

The new planned obsolescence.