Reduce power of a microwave oven?

Discussion in 'Electronic Repair' started by mike, Jan 18, 2011.

1. mikeGuest

My 27 year old microwave oven was down below 400W output and taking a long
time to heat my coffee.
So, I went out and bought a 1100W one.
Big mistake.
It works fine on coffee, but WAY overcooks small stuff.
Yes, it has a power level setting, but the on-time is 15 seconds
and they modulate the off-time.
I tried to heat a frozen hamburger patty. It boils the liquid around
the outside for 15 seconds, but the inside is still frozen.
This really messes up the cheese stuck to it. If I leave it in
the frozen burger, it comes out awful.

What are my options for reducing power?
Yes, I can stick in a pot of water to absorb energy, but I'm
looking for a more elegant solution.
I assume there's nothing I can do on the primary side, cause of the
filament voltage requirements.
Assuming I can find a switch that can take the voltage and current,
can I switch the value of the big cap? Not much else in there to play with.

Alternatively, there's stuff they put in the bottom of microwave popcorn
that heats up from microwaves. What is that stuff? Maybe I can find a
pan with that in the bottom to average out the energy over time.
There's a "as seen on TV" serving plate that you heat in the microwave.
It's made of granite. What is it in the granite that gets heated?
IF I could find a square of floor tile in ceramic or granite, ceramic is
more easily available, I could stick one of them in the bottom of the oven.

Suggestions?
Thanks, mike

mike, Jan 18, 2011

2. William SommerwerckGuest

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

I always assumed variable power was simple duty-cycle variation --
pulse-width-modulation -- over a fraction of a second. That the "on" time
would be fixed at 15 seconds (!!!), with the off time varied, is absurd. It
would produce exactly the effect you see.

There's also the possibility your sample is defective.

The stuff at the bottom of a microwave-popcorn bag is called a susceptor
sheet. I think it's a ferrite material, but I'm not sure.

http://en.wikipedia.org/wiki/Susceptor

Without any food to absorb heat from the susceptor, it would probably
overheat and burn fairly quickly.

You might try putting a brick on the oven, on the remote chance
fire-hardened clay absorbs microwaves. Bricks made with metallic colorants
might be the best place to start.

William Sommerwerck, Jan 18, 2011

3. mikeGuest

Michael A. Terrell wrote:
> mike wrote:
>> My 27 year old microwave oven was down below 400W output and taking a long
>> time to heat my coffee.
>> So, I went out and bought a 1100W one.
>> Big mistake.
>> It works fine on coffee, but WAY overcooks small stuff.
>> Yes, it has a power level setting, but the on-time is 15 seconds
>> and they modulate the off-time.
>> I tried to heat a frozen hamburger patty. It boils the liquid around
>> the outside for 15 seconds, but the inside is still frozen.
>> This really messes up the cheese stuck to it. If I leave it in
>> the frozen burger, it comes out awful.
>>
>> What are my options for reducing power?
>> Yes, I can stick in a pot of water to absorb energy, but I'm
>> looking for a more elegant solution.
>> I assume there's nothing I can do on the primary side, cause of the
>> filament voltage requirements.
>> Assuming I can find a switch that can take the voltage and current,
>> can I switch the value of the big cap? Not much else in there to play with.
>>
>> Alternatively, there's stuff they put in the bottom of microwave popcorn
>> that heats up from microwaves. What is that stuff? Maybe I can find a
>> pan with that in the bottom to average out the energy over time.
>> There's a "as seen on TV" serving plate that you heat in the microwave.
>> It's made of granite. What is it in the granite that gets heated?
>> IF I could find a square of floor tile in ceramic or granite, ceramic is
>> more easily available, I could stick one of them in the bottom of the oven.
>>
>> Suggestions?

>
>
> RTFM to see how to set the cook power.

Amazing!!!
RTFM reply when I stated EXACTLY how the power setting works.
>
>

mike, Jan 19, 2011
4. mikeGuest

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.
>
> I always assumed variable power was simple duty-cycle variation --
> pulse-width-modulation -- over a fraction of a second. That the "on" time
> would be fixed at 15 seconds (!!!), with the off time varied, is absurd. It
> would produce exactly the effect you see.

Yep, that's the way most of 'em work. The problem is the filament in
the magnetron. Much shorter and you don't get any power out cause
the filament ain't hot yet. With enough mass inside the oven, it
averages out pretty well. For a single frozen hamburger at 1100W, not
so much.

Yes, you can buy a microwave with fine-grained setting of continuous
power at most any retailer...for 3X the price.
They have to keep the filament hot while reducing the power. Much more
complicated and not a commodity item >> much higher price.
>
> There's also the possibility your sample is defective.
>
> The stuff at the bottom of a microwave-popcorn bag is called a susceptor
> sheet. I think it's a ferrite material, but I'm not sure.
>
> http://en.wikipedia.org/wiki/Susceptor
>
> Without any food to absorb heat from the susceptor, it would probably
> overheat and burn fairly quickly.

They used to make browning plates with some kind of susceptor in the bottom.
Seems the only place you get 'em today is from TV infomercials at
high prices or on ebay at antique prices.

I do have a microwavable trivet that claims to be made from granite.
Gets hot alright, but it's encased in plastic and not well coupled
to whatever you put on it. A couple of experiments suggest that
while it does divert significant power, it will probably overheat
trying to do what I want.

A cup of water solves the problem, but it's not very elegant.
>
> You might try putting a brick on the oven, on the remote chance
> fire-hardened clay absorbs microwaves. Bricks made with metallic colorants
> might be the best place to start.

There's considerable range of microwave absorbency. I was hoping to find
some kind of commonly available ceramic, like floor tile, that
would work. That's why I asked for input.
Wonder what Home Depot would think if I packed tile samples
into the employee lounge and stuffed 'em into the microwave?
>
>

mike, Jan 19, 2011
5. David NebenzahlGuest

On 1/18/2011 5:55 PM mike spake thus:

> Michael A. Terrell wrote:
>
>> mike wrote:
>>
>>> My 27 year old microwave oven was down below 400W output and
>>> taking a long time to heat my coffee. So, I went out and bought a
>>> 1100W one. Big mistake. It works fine on coffee, but WAY
>>> overcooks small stuff. Yes, it has a power level setting, but the
>>> on-time is 15 seconds and they modulate the off-time. I tried to
>>> heat a frozen hamburger patty. It boils the liquid around the
>>> outside for 15 seconds, but the inside is still frozen. This
>>> really messes up the cheese stuck to it. If I leave it in the
>>> frozen burger, it comes out awful.
>>>
>>> What are my options for reducing power?

[snip]

>>> Suggestions?

>>
>> RTFM to see how to set the cook power.

>
> Amazing!!!
> RTFM reply when I stated EXACTLY how the power setting works.

Mr. Terrell apparently shoots from the hip and never apologizes.

--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

David Nebenzahl, Jan 19, 2011
6. Fred McKenzieGuest

In article <ih536g\$rco\$-september.org>,
mike <> wrote:

> Yes, it has a power level setting, but the on-time is 15 seconds
> and they modulate the off-time.
> I tried to heat a frozen hamburger patty. It boils the liquid around
> the outside for 15 seconds, but the inside is still frozen.

Mike-

Does the new microwave have a Defrost option? If so, does it also cook
for 15 seconds at full power?

I had a small microwave back in the 70s that had a low power setting.
My memory is a little hazy, but I think the low power setting switched a
capacitor in series with the high voltage transformer primary. It acted
as a ballast to reduce magnetron voltage.

Fred

Fred McKenzie, Jan 19, 2011
7. PeterDGuest

On Tue, 18 Jan 2011 20:35:49 -0500, "Michael A. Terrell"
<> wrote:

>
>mike wrote:
>>
>> My 27 year old microwave oven was down below 400W output and taking a long
>> time to heat my coffee.
>> So, I went out and bought a 1100W one.
>> Big mistake.
>> It works fine on coffee, but WAY overcooks small stuff.
>> Yes, it has a power level setting, but the on-time is 15 seconds
>> and they modulate the off-time.
>> I tried to heat a frozen hamburger patty. It boils the liquid around
>> the outside for 15 seconds, but the inside is still frozen.
>> This really messes up the cheese stuck to it. If I leave it in
>> the frozen burger, it comes out awful.
>>
>> What are my options for reducing power?
>> Yes, I can stick in a pot of water to absorb energy, but I'm
>> looking for a more elegant solution.
>> I assume there's nothing I can do on the primary side, cause of the
>> filament voltage requirements.
>> Assuming I can find a switch that can take the voltage and current,
>> can I switch the value of the big cap? Not much else in there to play with.
>>
>> Alternatively, there's stuff they put in the bottom of microwave popcorn
>> that heats up from microwaves. What is that stuff? Maybe I can find a
>> pan with that in the bottom to average out the energy over time.
>> There's a "as seen on TV" serving plate that you heat in the microwave.
>> It's made of granite. What is it in the granite that gets heated?
>> IF I could find a square of floor tile in ceramic or granite, ceramic is
>> more easily available, I could stick one of them in the bottom of the oven.
>>
>> Suggestions?

>
>
> RTFM to see how to set the cook power.

Or use the defrost cycle!

PeterD, Jan 19, 2011
8. William SommerwerckGuest

>> 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.

>> I always assumed variable power was simple duty-cycle variation --
>> pulse-width-modulation -- over a fraction of a second. That the "on" time
>> would be fixed at 15 seconds (!!!), with the off time varied, is absurd.

It
>> would produce exactly the effect you see.

> Yep, that's the way most of 'em work. The problem is the filament in
> the magnetron. Much shorter and you don't get any power out cause
> the filament ain't hot yet. With enough mass inside the oven, it
> averages out pretty well. For a single frozen hamburger at 1100W, not
> so much.

I've never heard of varying a magnetron's power by adjusting its filament
voltage! I've always ASS+U+MEd there was some way of turning the tube on and
off by varying an electrode voltage. (Simply pulsing the anode voltage would
produce variable output.)

William Sommerwerck, Jan 19, 2011
9. William SommerwerckGuest

> Bacon, eggs, burger were some examples.

A microwave oven is ideal for bacon, because all it needs is a thorough
heating. Which is all a microwave oven does... It doesn't actully /cook/
anything.

William Sommerwerck, Jan 19, 2011
10. Lab1Guest

On 1/19/2011 2:07 AM, Fred McKenzie wrote:

>> Yes, it has a power level setting, but the on-time is 15 seconds
>> and they modulate the off-time.
>> I tried to heat a frozen hamburger patty. It boils the liquid around
>> the outside for 15 seconds, but the inside is still frozen.

>
> Does the new microwave have a Defrost option? If so, does it also cook
> for 15 seconds at full power?

Many new microwaves have and auto-defrost function (also usually an
auto-reheat) that measures the humidity while firing the magnetron for
short bursts. It runs this cyclically for a preset time based on your
food selection and weight while it calculates the actual time it should
take to defrost the food. Then it usually beeps once and finally runs
the defrost cycle that it calculated.

I find this works quite well once you get the hang of it.

--
-Scott

Lab1, Jan 19, 2011
11. William SommerwerckGuest

> All of the bog-standard microwave ovens that I've owned have worked
exactly
> like that - and it was fine when they were the 'standard' 600 or 650 watts
> of a few years ago. However, now they are all 850 / 900 / 1000 watts, it's

a
> crap system of power control. The one I have at the moment, does exactly

as
> the poster's does when set to say 60% power. It's like 15 seconds on at

full
> chat, followed by 20 seconds at full off. 60% is what's needed for heating

a
> can of soup in a reasonable time to a reasonable temperature. And it's ok

if
> it's just a full liquid soup like say tomato. But as soon as you try to do
> it with anything like perhaps vegetable, 15 seconds of microwaves at 850
> watts, is enough to start exploding the peas or beans or barley grains,

all
> over the inside of the rotten thing. 600 watts didn't used to do this. If
> you go to the next step down - ie 40% power - it takes forever to get the
> bulk liquid of the soup up to an edible temperature.

Fascinating. (In the correct Spock sense... "Fascinating I reserve for the
unexpected.")

I have a high-power GE microwave oven cum exhaust hood. Many foods -- such
as soup or oatmeal -- must be heated at half power (give or take), or you
get localized boiling, sometimes very quickly. I've never seen this happen
with reduced power. The oven always acts as if the magnetron is being
rapidly pulsed.

May I publicly apologize for believing that manufacturers ever use the least
bit of common sense when designing products?

William Sommerwerck, Jan 19, 2011
12. William SommerwerckGuest

"Arfa Daily" <> wrote in message
news:7qEZo.371\$2...
> "William Sommerwerck" <> wrote in message
> news:ih6qji\$7hl\$-september.org...

>>> Bacon, eggs, burger were some examples.

>> A microwave oven is ideal for bacon, because all it needs is a thorough
>> heating. Which is all a microwave oven does... It doesn't actully /cook/
>> anything.

> I seem to remember that we had this discussion once before some
> years back. It depends on how you define the word "cook". Using the
> traditional definition of 'preparing food by use of heat' I would contend
> that this is exactly what a microwave oven does - or am I missing
> something ... ? If I am, then what *is* cooking that a conventional
> oven does differently ?

Your perfectly logical definition seems sufficiently generic to include
microwave ovens. In practice, "cooking" refers to either immersing
the-thing-to-be-prepared in a cavity full of hot air...

"Yeah, Sommerwerck -- yer mouth."

....(baking, roasting) or applying heat directly to it (frying) or from a
nearby source (broiling, grilling). Microwave "cooking" does none of
these -- it simply heats the-thing-to-be-prepared from the inside.

Oddly, the Wikipedia article claims that microwave cooking heats food more
evenly than any other method, when, in fact, it heats from the outside in,
as does every other cooking method, and can be extremely uneven, if part of
the dish is sitting in a standing-wave node.

William Sommerwerck, Jan 19, 2011
13. William SommerwerckGuest

William Sommerwerck, Jan 19, 2011
14. PeterDGuest

On Wed, 19 Jan 2011 05:57:24 -0800, "William Sommerwerck"
<> wrote:

>> Bacon, eggs, burger were some examples.

>
>A microwave oven is ideal for bacon, because all it needs is a thorough
>heating. Which is all a microwave oven does... It doesn't actully /cook/
>anything.
>

let's face it, most cooking is just heating.

PeterD, Jan 19, 2011
15. PeterDGuest

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.

PeterD, Jan 19, 2011
16. William SommerwerckGuest

>> 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...

> 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.

I could easily test this with frozen bagels. Do you want me to? I'm not much
in the mood.

William Sommerwerck, Jan 19, 2011
17. Jeff LaymanGuest

On 19/01/2011 06:39, Dave Platt wrote:
> In article<ih5hng\$bfu\$-september.org>,
> mike<> wrote:
>
>> Yep, that's the way most of 'em work. The problem is the filament in
>> the magnetron. Much shorter and you don't get any power out cause
>> the filament ain't hot yet. With enough mass inside the oven, it
>> averages out pretty well. For a single frozen hamburger at 1100W, not
>> so much.
>>
>> Yes, you can buy a microwave with fine-grained setting of continuous
>> power at most any retailer...for 3X the price.
>> They have to keep the filament hot while reducing the power. Much more
>> complicated and not a commodity item>> much higher price.

>
> Not that much higher these days, I think. The Toshiba "inverter"
> microwave ovens have a variable power level of this general sort, and
> they're commodity items to the extent of being buyable at Costco and
> probably other big-box stores. They're somewhat more expensive than
> ovens fixed-power magnetrons, but not all that much.
>
> However... I had one, and it died within a couple of years in home
> use. Our previous microwave had lasted for a couple of decades. I'm
> not sure whether this was an odd failure in this unit, or was
> characteristic of Toshiba inverter microwaves in general, or just an
> result of the "race to the bottom, in price and in quality" which
> seems to be affecting the whole consumer-electronics business these
> days.
>
> I bought a fixed-power-output commercial-service Amana as a
> replacement, in the hopes that it'll last rather longer than the
> Toshiba did.
>

My Panasonic has an inverter. Works OK, and and an energy meter
confirmed that it doesn't just cycle from full power to off when running
at lower power levels.

But it does tempt you to experiment. Even though the guidebook warns
against trying to "boil" a perfectly cooked egg in its shell, I thought
it worth trying using lower power levels. The first egg was perfect,
using a rather complicated cooking schedule. The second was very soft -
barely cooked. The third I'd rather forget, but it took a long time to
clean the oven, and SWMBO wasn't amused as she was standing almost next
to the door when it was blown open. It also took me some time to repair
the safety lock...

--

Jeff

Jeff Layman, Jan 19, 2011
18. David NebenzahlGuest

On 1/19/2011 9:24 AM William Sommerwerck spake thus:

> Oddly, the Wikipedia article claims that microwave cooking heats food more
> evenly than any other method, when, in fact, it heats from the outside in,
> as does every other cooking method, and can be extremely uneven, if part of
> the dish is sitting in a standing-wave node.

.... which should give further pause to those who claim that Wikipedia is
full of good, accurate information ...

--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.

David Nebenzahl, Jan 19, 2011
19. mikeGuest

Michael A. Terrell wrote:
> mike wrote:
>> Michael A. Terrell wrote:
>>> mike wrote:
>>>> My 27 year old microwave oven was down below 400W output and taking a long
>>>> time to heat my coffee.
>>>> So, I went out and bought a 1100W one.
>>>> Big mistake.
>>>> It works fine on coffee, but WAY overcooks small stuff.
>>>> Yes, it has a power level setting, but the on-time is 15 seconds
>>>> and they modulate the off-time.
>>>> I tried to heat a frozen hamburger patty. It boils the liquid around
>>>> the outside for 15 seconds, but the inside is still frozen.
>>>> This really messes up the cheese stuck to it. If I leave it in
>>>> the frozen burger, it comes out awful.
>>>>
>>>> What are my options for reducing power?
>>>> Yes, I can stick in a pot of water to absorb energy, but I'm
>>>> looking for a more elegant solution.
>>>> I assume there's nothing I can do on the primary side, cause of the
>>>> filament voltage requirements.
>>>> Assuming I can find a switch that can take the voltage and current,
>>>> can I switch the value of the big cap? Not much else in there to play with.
>>>>
>>>> Alternatively, there's stuff they put in the bottom of microwave popcorn
>>>> that heats up from microwaves. What is that stuff? Maybe I can find a
>>>> pan with that in the bottom to average out the energy over time.
>>>> There's a "as seen on TV" serving plate that you heat in the microwave.
>>>> It's made of granite. What is it in the granite that gets heated?
>>>> IF I could find a square of floor tile in ceramic or granite, ceramic is
>>>> more easily available, I could stick one of them in the bottom of the oven.
>>>>
>>>> Suggestions?
>>>
>>> RTFM to see how to set the cook power.

>> Amazing!!!
>> RTFM reply when I stated EXACTLY how the power setting works.

>
>
> Then stick a damn glass of water in the oven to adsorb some of the
> energy.
>

You're just DETERMINED NOT TO READ the original posting...where I
mentioned that too.
Although, I'd not considered adsorption as a relevant process.

mike, Jan 19, 2011
20. William SommerwerckGuest

"David Nebenzahl" <> wrote in message
news:4d374867\$0\$2362\$...
> On 1/19/2011 9:24 AM William Sommerwerck spake thus:

>> Oddly, the Wikipedia article claims that microwave cooking heats food

more
>> evenly than any other method, when, in fact, it heats from the outside

in,
>> as does every other cooking method, and can be extremely uneven, if part

of
>> the dish is sitting in a standing-wave node.

> ... which should give further pause to those who claim that Wikipedia is
> full of good, accurate information ...

It is. No one is claiming it's always absolutely perfect.

William Sommerwerck, Jan 19, 2011