Radiation hazards from inefficient microwave oven?

[[email protected]]

Hello,

My microwave oven is old, and has had the usual abuse (spills,
occasional sparks because of foil, etc).

After a few years, I notice that it heats up a cup of water slower than
it used to. Several explanations are possible, but I'm wondering about
this one:
Is the radiation likely to be leaking out into the rest of the kitchen?
Or is it probably something more benign, such as less power being fed
to the oscillator?

Thank you very much!

Ted Shoemaker

 

[Homer J Simpson]

After a few years, I notice that it heats up a cup of water slower than
it used to.

Bigger cup? Colder water? I got a tester at the dollar store - no leakage.

 

[[email protected]]

Hello,

My microwave oven is old, and has had the usual abuse (spills,
occasional sparks because of foil, etc).

After a few years, I notice that it heats up a cup of water slower than
it used to. Several explanations are possible, but I'm wondering about
this one:
Is the radiation likely to be leaking out into the rest of the kitchen?
Or is it probably something more benign, such as less power being fed
to the oscillator?

Thank you very much!

Ted Shoemaker

Probably magnetron emission falling. Its worth giving it a good clean
out though, especially where the microwaves enter the cooking caivty,
in case theres some piece of carbon glowing hot somewhere.

Leakage is not likely on modern ovens, unless the cooking cavity is
rusted right through or its been seriously abused.


NT

 

[Jamie]

Hello,

My microwave oven is old, and has had the usual abuse (spills,
occasional sparks because of foil, etc).

After a few years, I notice that it heats up a cup of water slower than
it used to. Several explanations are possible, but I'm wondering about
this one:
Is the radiation likely to be leaking out into the rest of the kitchen?
Or is it probably something more benign, such as less power being fed
to the oscillator?

Thank you very much!

Ted Shoemaker

well if you don't see any thing green growing around the
out side of the unit and you haven't developed any unexplainable
cancers while sitting at the breakfast table every more for those
many of years? i would say you most likely have a depleted
magnetron tube..

 

[JANA]

It's common that the magnetron starts to go weak after a number of years.
Also, the main capacitor in the power supply may be starting to fail.

If you are interested to know what is failing, you can take the microwave
oven over to a local service centre to find out.

From experience, once a microwave oven is more than about 4 years old, I
would not invest very much in servicing it.

--

JANA
_____


Hello,

My microwave oven is old, and has had the usual abuse (spills,
occasional sparks because of foil, etc).

After a few years, I notice that it heats up a cup of water slower than
it used to. Several explanations are possible, but I'm wondering about
this one:
Is the radiation likely to be leaking out into the rest of the kitchen?
Or is it probably something more benign, such as less power being fed
to the oscillator?

Thank you very much!

Ted Shoemaker

 

[Sam Goldwasser]

It's common that the magnetron starts to go weak after a number of years.
Also, the main capacitor in the power supply may be starting to fail.

If you are interested to know what is failing, you can take the microwave
oven over to a local service centre to find out.

From experience, once a microwave oven is more than about 4 years old, I
would not invest very much in servicing it.

Hmmmmm. Our Sharp is about 20 years old now and as far as I can tell,
works as well as the day it was bought.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

 

[[email protected]]

Hmmmmm. Our Sharp is about 20 years old now and as far as I can tell,
works as well as the day it was bought.

yes, thats more my experience too. Many people have newness disease it
seems.


NT

 

[Homer J Simpson]

Hmmmmm. Our Sharp is about 20 years old now and as far as I can tell,
works as well as the day it was bought.

"Microwaves don't burn out. They rust out". The one I bought in 1985 and
used daily is still running. Two of the little plastic rivets that hold the
spinner cover on cracked, that's all.

 

[default]

Hello,

My microwave oven is old, and has had the usual abuse (spills,
occasional sparks because of foil, etc).

After a few years, I notice that it heats up a cup of water slower than
it used to. Several explanations are possible, but I'm wondering about
this one:
Is the radiation likely to be leaking out into the rest of the kitchen?
Or is it probably something more benign, such as less power being fed
to the oscillator?

Thank you very much!

Ted Shoemaker

Unlikely it is leaking. More likely the magnetron isn't working as
well or cap or diode bad. They all seem to get weaker over time.

You should be able to calculate the power and how long it should water
to boil - I did come across a reference to that as a test some time
ago when I had the same problem.

 

[William R. Walsh]

Hi!

Is the radiation likely to be leaking out into the rest of the kitchen?

No, probably not. If you aren't sure, go buy a microwave radiation tester
and follow the directions included with it to find out. Keep in mind that
while they aren't the most accurate thing around, they will detect serious
problems.

As some have mentioned, the magnetron tube may be wearing out. However, I
think you'll find the trouble may be elsewhere. Just about all microwaves
have an electric fan inside that cools the magnetron to keep it from
overheating.

If this fan is sticky, gummy or can't get up to full speed, this may be the
only problem. Even if the fan sounds fine, it's worth taking a look at the
vents on the unit to be sure they are not plugged.

If the oven checks out, look at your household wiring. Perhaps the circuit
you've got the oven plugged into cannot deliver the power needed to make the
microwave work efficiently.

William

 

[Michael A. Terrell]

It's common that the magnetron starts to go weak after a number of years.
Also, the main capacitor in the power supply may be starting to fail.

That is an oil filled film HV capacitor. When they "Start to fail"
they don't waste your time. They are generally either good, open, or a
dead short. All the bad ones I've seen were a dead short, but i had a
nice pile of good used ones from scrap ovens. A lot of controller boards
die here in Florida with all of the lightning, so I save the
transformers, Magnetrons and HV parts. Come to think of it, I've never
had a new microwave oven, and the most I've paid for one was $2 for one
with a shorted interlock switch. I have three working units right now
that were given to me, all in like new condition.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[[email protected]]

No, probably not. If you aren't sure, go buy a microwave radiation tester
and follow the directions included with it to find out. Keep in mind that
while they aren't the most accurate thing around, they will detect serious
problems.

those are pointless. A visual inspection to ensure no rust holes and
the door closes is the only leakage test relevant to modern ovens. For
30+ year old ovens things are different, and the best advice is to dump
them.

As some have mentioned, the magnetron tube may be wearing out. However, I
think you'll find the trouble may be elsewhere. Just about all microwaves
have an electric fan inside that cools the magnetron to keep it from
overheating.

If this fan is sticky, gummy or can't get up to full speed, this may be the
only problem. Even if the fan sounds fine, it's worth taking a look at the
vents on the unit to be sure they are not plugged.

that wouldnt affect cooking power delivery afaik.

If the oven checks out, look at your household wiring. Perhaps the circuit
you've got the oven plugged into cannot deliver the power needed to make the
microwave work efficiently.

smoke or flames coming outta the wall socket would indicate that
problem. Otherwise the oven will be getting the power it wants.


NT

 

[Dan_Musicant]

:
::
:> After a few years, I notice that it heats up a cup of water slower than
:> it used to.
:
:Bigger cup? Colder water? I got a tester at the dollar store - no leakage.
What kind of tester did you get for a buck?

 

[Dan_Musicant]

On Mon, 04 Sep 2006 05:26:50 GMT, "Michael A. Terrell"

:JANA wrote:
:>
:> It's common that the magnetron starts to go weak after a number of years.
:> Also, the main capacitor in the power supply may be starting to fail.
:
:
: That is an oil filled film HV capacitor. When they "Start to fail"
:they don't waste your time. They are generally either good, open, or a
:dead short. All the bad ones I've seen were a dead short, but i had a
:nice pile of good used ones from scrap ovens. A lot of controller boards
:die here in Florida with all of the lightning, so I save the
:transformers, Magnetrons and HV parts. Come to think of it, I've never
:had a new microwave oven, and the most I've paid for one was $2 for one
:with a shorted interlock switch. I have three working units right now
:that were given to me, all in like new condition.

I found a MW oven in the street a few weeks ago and brought it home
thinking it either works or I'll tear it open and salvage the magnets.

It seemed dead, but yesterday I opened it up and the fuse tested dead
(250v, 15amp). I had a 125v 15 amp fuse and putting it in, the oven
appears to work.

Two questions:

1. Can I leave that fuse in there or should I get a 250v 15 amp instead?

2. A MW oven troubleshooting site says:

NOTE: Fuses do not usually blow on their own. A fuse may blow because of
problems with the interlock switches or with high voltage circuitry. It
is also possible, though rare, that a power surge will cause a fuse to
blow.

I have a MW oven I prefer, and figure to store this in my garage for
that day when my current one dies (they always seem to eventually). What
are the interlock switches and can I fix a bad one? Or is it possible I
could fix a high voltage circuitry problem? TIA for some help.

Dan

 

[Andy Cuffe]

I found a MW oven in the street a few weeks ago and brought it home
thinking it either works or I'll tear it open and salvage the magnets.

It seemed dead, but yesterday I opened it up and the fuse tested dead
(250v, 15amp). I had a 125v 15 amp fuse and putting it in, the oven
appears to work.

Two questions:

1. Can I leave that fuse in there or should I get a 250v 15 amp instead?

2. A MW oven troubleshooting site says:

NOTE: Fuses do not usually blow on their own. A fuse may blow because of
problems with the interlock switches or with high voltage circuitry. It
is also possible, though rare, that a power surge will cause a fuse to
blow.

I have a MW oven I prefer, and figure to store this in my garage for
that day when my current one dies (they always seem to eventually). What
are the interlock switches and can I fix a bad one? Or is it possible I
could fix a high voltage circuitry problem? TIA for some help.

Dan

I've seen quite a few microwaves that had blown fuses for no apparent
reason. There's a chance of an intermittent problem, but it is
probably fine. If it blows again, there is a definite problem that
needs to be repaired. A 125v fuse is fine as long as it's a 120v
microwave.
Andy Cuffe

[email protected]

 

[Michael A. Terrell]

On Mon, 04 Sep 2006 05:26:50 GMT, "Michael A. Terrell"

:JANA wrote:
:>
:> It's common that the magnetron starts to go weak after a number of years.
:> Also, the main capacitor in the power supply may be starting to fail.
:
:
: That is an oil filled film HV capacitor. When they "Start to fail"
:they don't waste your time. They are generally either good, open, or a
:dead short. All the bad ones I've seen were a dead short, but i had a
:nice pile of good used ones from scrap ovens. A lot of controller boards
:die here in Florida with all of the lightning, so I save the
:transformers, Magnetrons and HV parts. Come to think of it, I've never
:had a new microwave oven, and the most I've paid for one was $2 for one
:with a shorted interlock switch. I have three working units right now
:that were given to me, all in like new condition.

I found a MW oven in the street a few weeks ago and brought it home
thinking it either works or I'll tear it open and salvage the magnets.

It seemed dead, but yesterday I opened it up and the fuse tested dead
(250v, 15amp). I had a 125v 15 amp fuse and putting it in, the oven
appears to work.

Two questions:

1. Can I leave that fuse in there or should I get a 250v 15 amp instead?

2. A MW oven troubleshooting site says:

NOTE: Fuses do not usually blow on their own. A fuse may blow because of
problems with the interlock switches or with high voltage circuitry. It
is also possible, though rare, that a power surge will cause a fuse to
blow.

I have a MW oven I prefer, and figure to store this in my garage for
that day when my current one dies (they always seem to eventually). What
are the interlock switches and can I fix a bad one? Or is it possible I
could fix a high voltage circuitry problem? TIA for some help.

Dan

Was the original 250 V fuse a white ceramic? You do not want a
common 125 V fuse if the circuit requires the sand filled ceramic that
is made to prevent a ball of plasma from melting it the next time it
blows. It can do a lot of damage, or even start a fire.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[[email protected]]

JANA wrote:

:> It's common that the magnetron starts to go weak after a number of years.
:> Also, the main capacitor in the power supply may be starting to fail.
:
:
: That is an oil filled film HV capacitor. When they "Start to fail"
:they don't waste your time. They are generally either good, open, or a
:dead short. All the bad ones I've seen were a dead short, but i had a
:nice pile of good used ones from scrap ovens. A lot of controller boards
:die here in Florida with all of the lightning, so I save the
:transformers, Magnetrons and HV parts. Come to think of it, I've never
:had a new microwave oven, and the most I've paid for one was $2 for one
:with a shorted interlock switch. I have three working units right now
:that were given to me, all in like new condition.

I found a MW oven in the street a few weeks ago and brought it home
thinking it either works or I'll tear it open and salvage the magnets.

It seemed dead, but yesterday I opened it up and the fuse tested dead
(250v, 15amp). I had a 125v 15 amp fuse and putting it in, the oven
appears to work.

Two questions:

1. Can I leave that fuse in there or should I get a 250v 15 amp instead?

2. A MW oven troubleshooting site says:

NOTE: Fuses do not usually blow on their own. A fuse may blow because of
problems with the interlock switches or with high voltage circuitry. It
is also possible, though rare, that a power surge will cause a fuse to
blow.

I have a MW oven I prefer, and figure to store this in my garage for
that day when my current one dies (they always seem to eventually). What
are the interlock switches and can I fix a bad one? Or is it possible I
could fix a high voltage circuitry problem? TIA for some help.

Dan

If it doesnt blow again, fine. If it does, get rid of the cooker. Dont
muck with the interlock stuff unless you properly know what youre
doing, and you dont. The risk versus benefit is not at all worth it. A
wrongly done interlock can cook you, or part of you.

I've read that the very first microwave ovens had no interlock, you
could open the door with them cooking. Basic switches were retrofitted
following injuries.


NT

 

[Michael A. Terrell]

I've read that the very first microwave ovens had no interlock, you
could open the door with them cooking. Basic switches were retrofitted
following injuries.

I find that damn hard to believe, since they were developed by
Litton. Litton had a lot of experience in manufacturing RADAR and
Microwave transmitter parts as well as the safety requirements. These
fields have extreme safety requirements. The RADAR equipment I worked
on had multiple interlocks. The 2 MW pulse RADAR at Ft Rucker had three
sets of keyed interlocks that shut down different parts of the
transmitters. You had to remove the key to open each gate as you went
up the steps to the antenna on the roof. You kept the three keys in
your pocket while you were up there, and had to lock the gates in the
right sequence to turn the system back on.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[James Sweet]

I've seen quite a few microwaves that had blown fuses for no apparent
reason. There's a chance of an intermittent problem, but it is
probably fine. If it blows again, there is a definite problem that
needs to be repaired. A 125v fuse is fine as long as it's a 120v
microwave.

I've had the same experience, microwaves are the only appliance I've
ever encountered where replacing the fuse will truly fix the thing many
times. I think the interlock occasionally will stick for just long
enough to pop the fuse.

 

[James Sweet]

I find that damn hard to believe, since they were developed by
Litton. Litton had a lot of experience in manufacturing RADAR and
Microwave transmitter parts as well as the safety requirements. These
fields have extreme safety requirements. The RADAR equipment I worked
on had multiple interlocks. The 2 MW pulse RADAR at Ft Rucker had three
sets of keyed interlocks that shut down different parts of the
transmitters. You had to remove the key to open each gate as you went
up the steps to the antenna on the roof. You kept the three keys in
your pocket while you were up there, and had to lock the gates in the
right sequence to turn the system back on.

The oldest microwave I've ever used was an ancient Amana RadarRange my
grandparents had, I believe it was early 70's vintage. When I was a kid
we had an enormous Litton 1200W oven from the late 70s, both of those
would stop when the door was opened.

I did encounter an early 80's microwave once that would keep running, it
was obviously a defective interlock setup, I opened the door and it took
a moment to register that it hadn't shut off.