Reduce power of a microwave oven?
mike
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
William Sommerwerck
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.
Michael A. Terrell
RTFM to see how to set the cook power.
--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.
mike
Amazing!!!
RTFM reply when I stated EXACTLY how the power setting works.
How about RTFOP?
>
>
mike
> 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?
>
>
David Nebenzahl
> 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.
> How about RTFOP?
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.
Fred McKenzie
mike <spa...@gmail.com> 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
Dave Platt
mike <spa...@gmail.com> 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.
--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Wild_Bill
power levels that suit your needs.
I haven't looked at MWOs lately, but the revolving turntable should probably
be a major consideration.
From many years ago, I found that trying to cook numerous types of foods in
a microwave provided awful results, and never bothered to try them in more
advanced models.
Bacon, eggs, burger were some examples.
The fairly large MWO I use now was given to me a number of years ago, and
suits my needs for the types of foods that I want to be microwaved.
The manual has so many different types of cycles, that I don't even bother
to try to remember them.
I stick with the basic operations, which limits what the MWO will be used
for, but that's not a problem for me.
Typical MWOs aren't a good substitute for an actual range/stove (and
appropriate cookware, talent, time etc).
Also, one generally needs to find the types/brands of processed foods that
provide the user with something desirable to their own tastes.
The top crust of a pot pie should be browned.. the Marie Callendar(?) frozen
pies have a metallic grid made into the top of the box, and the crust always
browns (may not work with low-powered MWOs, I don't know for sure). The
minimum power recommended is marked on the box.
The 1 lb size pies are a decent portion, and taste good.. allow ample time
for cooling.
I don't have them anymore, but at one time I had a set of microwave dishes
with covers that were very useful.
They were a tan bakelite/melmac-type material with metal flakes visible in
the material.. they were a fairly common brand name in the U.S. but I'm not
sure what it was.
Anyway, I could get varied results with lid on , off or turned 45 degrees
(square dishes), which are all common techniques with conventional cooking.
So, the types of accessories and different techniques will yield more
options, and very different results.
I've found certain techniques that produce results which are more to my
personal liking.. such as always wrap/cover a sandwich in paper towel to
heat (prevents the bread/bun from getting hard spots without becoming
soggy), cover cold pizza also with paper towel, or better yet, eat it cold.
There are various options.. placing flat foods between two paper plates, or
tall sandwiches between two paper bowls.
There are various commercial plastic products/accessories for MWO use, but
those require washing.. disposable paper (not plastic/styrofoam) plates and
bowls, and plastic utensils don't.
I never put uncovered liquids or other types of foods that are a combination
of food/liquid in the MWO, I always use a paper plate as a cover. I can't
stand seeing a dirty MWO, and it's far easier to prevent eruptions than to
clean them up.
But then, I generally always wipe the interior down with a paper towel
dampened with 60/40% water/alcohol mixture that has a few drops of liquid
soap added per pint, to wipe out the condensed moisture, every time I use
the MWO.
--
Cheers,
WB
.............
"mike" <spa...@gmail.com> wrote in message
news:ih536g$rco$1...@news.eternal-september.org...
PeterD
Or use the defrost cycle!
William Sommerwerck
>> 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
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.
Lab1
>> 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
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:ih6qf4$6sk$1...@news.eternal-september.org...
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.
Arfa
Arfa Daily
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:ih6qji$7hl$1...@news.eternal-september.org...
I seem to remember that we had this discussion once before some years back.
It depends on how you define the word "cook". Using the traditional
definition of 'preparing food by use of heat' I would contend that this is
exactly what a microwave oven does - or am I missing something ... ? If I
am, then what *is* cooking that a conventional oven does differently ?
Arfa
William Sommerwerck
exactly
> like that - and it was fine when they were the 'standard' 600 or 650 watts
> of a few years ago. However, now they are all 850 / 900 / 1000 watts, it's
a
> crap system of power control. The one I have at the moment, does exactly
as
> the poster's does when set to say 60% power. It's like 15 seconds on at
full
> chat, followed by 20 seconds at full off. 60% is what's needed for heating
a
> can of soup in a reasonable time to a reasonable temperature. And it's ok
if
> it's just a full liquid soup like say tomato. But as soon as you try to do
> it with anything like perhaps vegetable, 15 seconds of microwaves at 850
> watts, is enough to start exploding the peas or beans or barley grains,
all
> over the inside of the rotten thing. 600 watts didn't used to do this. If
> you go to the next step down - ie 40% power - it takes forever to get the
> bulk liquid of the soup up to an edible temperature.
Fascinating. (In the correct Spock sense... "Fascinating I reserve for the
unexpected.")
I have a high-power GE microwave oven cum exhaust hood. Many foods -- such
as soup or oatmeal -- must be heated at half power (give or take), or you
get localized boiling, sometimes very quickly. I've never seen this happen
with reduced power. The oven always acts as if the magnetron is being
rapidly pulsed.
May I publicly apologize for believing that manufacturers ever use the least
bit of common sense when designing products?
William Sommerwerck
news:7qEZo.371$S16...@newsfe20.ams2...
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
It was filed for in 1975.
http://ip.com/patent/US4041267
PeterD
let's face it, most cooking is just heating.
PeterD
<grizzle...@comcast.net> 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.
William Sommerwerck
>> 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
> 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.
Jeff Layman
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
Michael A. Terrell
Why do things right, when you can whine online? ;-)
Michael A. Terrell
Then stick a damn glass of water in the oven to adsorb some of the
energy.
Wild_Bill
cooked means different things in different contexts.
Not raw.. safe to eat.
Beef color changed from pink to grey.
Internal temp of 180 F.
Cooked, meaning not raw, is hardly properly prepared to taste. A piece of
beef could be boiled to an internal temp of 180 F, and it's cooked, but I
wouldn't care to eat it prepared that way.. some people do.
If beef doesn't sear from being in contact with blazing hot air/reflected IR
heat (real oven), metal and/or fire, ya might as well be eating soy.
Beef roasted in a real oven will brown on the top/outside, but not in a
typical MWO.
For my tastes, the searing/browning of meats is what gives them good flavor,
not so much the seasoning.. with a few exceptions, fried chicken, for
example.
I prefer real oven or covered grill baked potatoes (or roasted in hot coals)
over microwaved potatoes.. it's a matter of preference. I haven't been able
to get crispy skins in a MWO.
Sure, the MWO potatoes are edible, but far less flavorful.
Many MWO dishes are pre-cooked processed stuff anyway.. not good food when
taken out of the package, but better when eaten warm/hot.
--
Cheers,
WB
.............
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:7qEZo.371$S16...@newsfe20.ams2...
>
David Nebenzahl
> 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 ...
larry moe 'n curly
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.
> Suggestions?
Put in a smaller high voltage capacitor?
Get an oven with inverter power control, like a Panasonic?
mike
mentioned that too.
Although, I'd not considered adsorption as a relevant process.
William Sommerwerck
news:4d374867$0$2362$8226...@news.adtechcomputers.com...
> 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.
mike
When I ask a question on line, I go to great lengths to describe the issue
in detail to keep the discussion from running off in all directions.
It rarely works, but I keep hoping that people will actually read the
info before shooting from the hip.
With this, and every other low-end non-inverter microwave oven I've ever
encountered, the power is adjusted by pulsing the magnetron in bursts
of approximately 15 seconds followed by an off-time required to get the
average power you programmed.
The RELEVANT number is the 15 second MINIMUM on-time. Doesn't matter
what buttons you push, you can't get an on-time less than 15 seconds unless
you program a single burst that's shorter.
If 15 seconds is long enough to boil the liquid in part of the payload,
defrosting can make a mess of things.
In this case, the "defrost" button has some algorithm that they don't
disclose
and I've been too lazy to reverse-engineer, but the minimum on-time
is still about 15 seconds.
It's a fundamental property of the design.
Lab1
Reminds me of this interesting video showing how microwave energy is
distributed inside a standard microwave...
http://www.youtube.com/watch?v=kAAXpKdQ-mk
--
-Scott
mike
I don't think there's anything you can do in the primary circuit.
The magnetron filament runs off the same transformer as the high voltage.
If you reduce the average input, you also reduce the average filament
voltage/temperature.
There are two basic issues that I can think of.
1) It takes time for the filament to come up to temperature.
2) The more you thermal-cycle the filament, the shorter the life.
The 15-seconds is a compromise that mostly works.
If you want to pulse the anode, you have to have a separate transformer for
the filament to keep it up to temperature while you pulse the anode.
Conceptually trivial, but it adds to the cost.
As I mentioned in the original posting, you probably can change the value
of the secondary cap, but that takes a high-voltage switch.
I'm interested to learn if anybody's done that. Or if there's
any theoretical basis for concluding that it's a bad idea.
mike
A triac can fix the relay issue. The problem is the thermal
time constant of the magnetron filament.
mike
>
> 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.
>
>> Suggestions?
>
> Put in a smaller high voltage capacitor?
Can you be a little more theoretical?
One reference suggested that the cap is actually
sized to resonate with the transformer. That would make
the change of cap value much more sensitive than just a power
ratio.
Relevant input?
Thanks, mike
>
> Get an oven with inverter power control, like a Panasonic?
whit3rd
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.
> 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.
The filament winding is on the same transformer as the HV, so the
filament turns off when the transformer isn't powered; and magnetrons
are a diode, it ONLY has the HV electrode available to control the
power.
If there were separate filament and HV transformers, the price would
reflect this 'feature' in unpleasant ways.
William Sommerwerck
news:f2ff7a8b-88eb-47b8...@a10g2000vby.googlegroups.com...
> The filament winding is on the same transformer as the HV,
> so the filament turns off when the transformer isn't powered;
> and magnetrons are a diode, it ONLY has the HV electrode
> available to control the power.
Ineed, the patent I referred to shows the filament secondary as part of the
main transformer. But the system presumably works.
> If there were separate filament and HV transformers, the price
> would reflect this 'feature' in unpleasant ways.
I can't imagine a separate filament transformer being /that/ expensive.
whit3rd
wrote:
> "whit3rd" <whit...@gmail.com> wrote in message
> Ineed, the patent I referred to shows the filament secondary as part of the
> main transformer. But the system presumably works.
>
> > If there were separate filament and HV transformers, the price
> > would reflect this 'feature' in unpleasant ways.
>
> I can't imagine a separate filament transformer being /that/ expensive.
But, you need to get multikilovolt safety testing on two magnetic
parts,
you need safe wiring in case the 'extra' wires come loose, and you
then require a media campaign to trumpet the added feature, and
a new model number for the finished product, which has to have a
snazzy front-panel rework to distinguish it from the unenhanced
model (which now sells at a different price point)... and the markup
on this $2 technical improvement can easily get you to $120 addon
at the retail store. The marketing department would like that to
be $225.
Yes, it's hard to imagine a separate filament transformer as
expensive.
The marketing department has expert imaginers to do the heavy work
of imagining the price upward. Ever upward. Excelsior!
Fleetie
You're right: Adsorption is definitely not relevant in this context!
Martin
David Nebenzahl
I guess I'm showing my ignorance here, as I don't know much about
magnetrons, but why can't you just let the filament burn while you cycle
the HV, like you'd do with any other ordinary tube? I mean, with other
tubes, it's OK to apply power to the heater without any anode voltage,
right?
Arfa Daily
"mike" <spa...@gmail.com> wrote in message
news:ih7ie4$nb5$1...@news.eternal-september.org...
All correct by my experience, also
Arfa
larry moe 'n curly
mike wrote:
> larry moe 'n curly 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.
> >
> >> Suggestions?
> >
> > Put in a smaller high voltage capacitor?
> Thanks for repeating one of my suggested options.
> Can you be a little more theoretical?
> One reference suggested that the cap is actually
> sized to resonate with the transformer. That would make
> the change of cap value much more sensitive than just a power
> ratio.
> Relevant input?
> Thanks, mike
I thought you meant adding another capacitor and switching between it
and the original.
I doubt the capacitor resonates because years ago someone mentioned a
line of microwaves being identical except for power rating, cavity
size, and the size of the high voltage capacitor, which ranged from
about 0.6uF to 1.0uF.
> > Get an oven with inverter power control, like a Panasonic?
> Simple matter of price ;-)
They're not as expensive as some people implied.
mike
>
> mike wrote:
>> larry moe 'n curly 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.
>>>> Suggestions?
>>> Put in a smaller high voltage capacitor?
>> Thanks for repeating one of my suggested options.
>> Can you be a little more theoretical?
>> One reference suggested that the cap is actually
>> sized to resonate with the transformer. That would make
>> the change of cap value much more sensitive than just a power
>> ratio.
>> Relevant input?
>> Thanks, mike
>
> I thought you meant adding another capacitor and switching between it
> and the original.
Yes, that's what I had in mind. All you need is a switch that can
handle that much volts safely...and maybe some means to make sure
that switching a charged cap doesn't explode the diode or the switch.
Some months ago, I had to replace the diode in my old one.
Hooked a resistor to a couple of clip leads and hooked them to the cap.
I never did find any of the resistor pieces. May have gotten swept up
when I cleaned up the puddle I made. ;-)
>
> I doubt the capacitor resonates because years ago someone mentioned a
> line of microwaves being identical except for power rating, cavity
> size, and the size of the high voltage capacitor, which ranged from
> about 0.6uF to 1.0uF.
>
>>> Get an oven with inverter power control, like a Panasonic?
>> Simple matter of price ;-)
>
> They're not as expensive as some people implied.
It's all relative. Paid $80 for mine. I did visit a few stores and the
inverter ones seemed to be almost 3x that and they don't go on sale
often. Knowing what I know now, I might have gone with the inverter.
Spilt milk now...
Arfa Daily
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4d3796cb$0$2374$8226...@news.adtechcomputers.com...
> On 1/19/2011 12:55 PM mike spake thus:
>
>> PeterD wrote:
>>
>>> On Wed, 19 Jan 2011 05:55:03 -0800, "William Sommerwerck"
>>> <grizzle...@comcast.net> 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?
>
In general, with indirectly heated types, no, it may not be ok. It has been
said that it can lead to cathode poisoning and sometimes cathode stripping.
In the good old days, HT standby switches often used to have a resistor
across them to keep a small bleed current running through the tubes,
however, I must admit that most modern amps that I see have no such
arrangement, so perhaps modern tubes are better at standing up to this sort
of abuse, or else it has become just a forgotten technique? Or maybe, it was
one of those 'myth' things that some manufacturers believed in, but wasn't
actually the case ? Eimac have published booklets about applying voltages in
the correct order and with the correct delays, to their RF Power
transmitting tubes, so I guess that there must be something in it,
somewhere. Are magnetrons indirectly heated ? I had a feeling that I had
seen somewhere that they weren't, and that the modulation introduced by the
AC on the filament, was insignificant compared to the output power at the
frequency of interest, so was ignored.
Arfa
Michael A. Terrell
mike wrote:
>
> Yes, that's what I had in mind. All you need is a switch that can
> handle that much volts safely...and maybe some means to make sure
> that switching a charged cap doesn't explode the diode or the switch.
>
> Some months ago, I had to replace the diode in my old one.
> Hooked a resistor to a couple of clip leads and hooked them to the cap.
> I never did find any of the resistor pieces. May have gotten swept up
> when I cleaned up the puddle I made. ;-)
You exceeded the maximum voltage rating of that resistor.
David Nebenzahl
> mike wrote:
>
>> Yes, that's what I had in mind. All you need is a switch that can
>> handle that much volts safely...and maybe some means to make sure
>> that switching a charged cap doesn't explode the diode or the switch.
>>
>> Some months ago, I had to replace the diode in my old one.
>> Hooked a resistor to a couple of clip leads and hooked them to the cap.
>> I never did find any of the resistor pieces. May have gotten swept up
>> when I cleaned up the puddle I made. ;-)
>
> You exceeded the maximum voltage rating of that resistor.
Gee, ya think?
Another incredibly useful 1-line post from the shoot-from-the-hip master ...
Michael A. Terrell
David Nebenzahl wrote:
>
> On 1/20/2011 4:44 AM Michael A. Terrell spake thus:
>
> > mike wrote:
> >
> >> Yes, that's what I had in mind. All you need is a switch that can
> >> handle that much volts safely...and maybe some means to make sure
> >> that switching a charged cap doesn't explode the diode or the switch.
> >>
> >> Some months ago, I had to replace the diode in my old one.
> >> Hooked a resistor to a couple of clip leads and hooked them to the cap.
> >> I never did find any of the resistor pieces. May have gotten swept up
> >> when I cleaned up the puddle I made. ;-)
> >
> > You exceeded the maximum voltage rating of that resistor.
>
> Gee, ya think?
>
> Another incredibly useful 1-line post from the shoot-from-the-hip master ...
And yet another snide, useless post from you.
isw
David Nebenzahl <nob...@but.us.chickens> wrote:
> On 1/19/2011 12:55 PM mike spake thus:
>
> > PeterD wrote:
> >
> >> On Wed, 19 Jan 2011 05:55:03 -0800, "William Sommerwerck"
> >> <grizzle...@comcast.net> 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.
Isaac
PeterD
The filament is a minor current, the main HV voltage is the issue. To
cycle off the transformer rapidly with a relay would likely result in
a relay lifetime of a few weeks at best.
I don't believe there ever was an issue with the filaments.
I agree, a triac could possibly be used, though you are talking about
swtiching as much as 1500 watts, inductive (because of the
transformer). Might be too expensive to find a triac that will take
that kind of abuse and survive!
PeterD
Neat trick since the filament emitts teh electrons...
Arfa Daily
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4d388c93$0$24073$8226...@news.adtechcomputers.com...
> On 1/20/2011 4:44 AM Michael A. Terrell spake thus:
>
>> mike wrote:
>>
>>> Yes, that's what I had in mind. All you need is a switch that can
>>> handle that much volts safely...and maybe some means to make sure
>>> that switching a charged cap doesn't explode the diode or the switch.
>>>
>>> Some months ago, I had to replace the diode in my old one.
>>> Hooked a resistor to a couple of clip leads and hooked them to the cap.
>>> I never did find any of the resistor pieces. May have gotten swept up
>>> when I cleaned up the puddle I made. ;-)
>>
>> You exceeded the maximum voltage rating of that resistor.
>
> Gee, ya think?
>
> Another incredibly useful 1-line post from the shoot-from-the-hip master
> ...
>
>
Actually, I think that it is quite a useful comment, as in my experience in
the electronics service business, many techs - particularly modern ones -
have no understanding that a resistor has a maximum working voltage rating,
and have even laughed at the very idea when I have suggested it to them,
until I have shown them in a component catalogue. I'm willing to bet that
prior to this exchange, there were more than a few reading what Michael
said, and doing just that ...
Arfa
David Nebenzahl
Well, I have to admit that it (maximum resistor voltage ratings) doesn't
often occur to me, simply because I don't work with HV. But the person
Mr. Terrell responded to above was certainly aware of why his resistor
got blown to smithereens. Hence my annoyance.
PeterD
Absolutely they do, but I suspect he also exceeded the power rating of
that resistor by a tiny bit as well... <g>
Michael A. Terrell
> that resistor by a tiny bit as well... <g>
You can exceed the voltage rating, without exceeding the power
rating. Pulse applications can be well below the rated wattage, yet arc
over internally.
Arfa Daily
"PeterD" <pet...@hipson.net> wrote in message
news:3kmlj6lm0h01cfshd...@4ax.com...
Well yeah. That too, I agree ! :-)
Arfa
Arfa Daily
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4d3a729e$0$15850$8226...@news.adtechcomputers.com...
I see that, but some other less experienced people reading the thread, may
well have learnt something from the comment. Still, all sorted now, and
everyone's up to speed on resistor voltage ratings !
Arfa
David Nebenzahl
> "David Nebenzahl" <nob...@but.us.chickens> wrote in message
> news:4d3a729e$0$15850$8226...@news.adtechcomputers.com...
>
>> On 1/21/2011 6:02 PM Arfa Daily spake thus:
>>>
>>> Actually, I think that it is quite a useful comment, as in my
>>> experience in the electronics service business, many techs -
>>> particularly modern ones - have no understanding that a resistor
>>> has a maximum working voltage rating, and have even laughed at
>>> the very idea when I have suggested it to them, until I have
>>> shown them in a component catalogue. I'm willing to bet that
>>> prior to this exchange, there were more than a few reading what
>>> Michael said, and doing just that ...
>>
>> Well, I have to admit that it (maximum resistor voltage ratings)
>> doesn't often occur to me, simply because I don't work with HV. But
>> the person Mr. Terrell responded to above was certainly aware of
>> why his resistor got blown to smithereens. Hence my annoyance.
>
> I see that, but some other less experienced people reading the thread, may
> well have learnt something from the comment. Still, all sorted now, and
> everyone's up to speed on resistor voltage ratings !
Well, point taken.
While we're on the subject, where would one get HV resistors, anyhow?
Any US suppliers?
Arfa Daily
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4d3b7943$0$2711$8226...@news.adtechcomputers.com...
> On 1/22/2011 7:56 AM Arfa Daily spake thus:
>
>> "David Nebenzahl" <nob...@but.us.chickens> wrote in message
>> news:4d3a729e$0$15850$8226...@news.adtechcomputers.com...
>>
>>> On 1/21/2011 6:02 PM Arfa Daily spake thus:
>>>>
>>>> Actually, I think that it is quite a useful comment, as in my
>>>> experience in the electronics service business, many techs -
>>>> particularly modern ones - have no understanding that a resistor
>>>> has a maximum working voltage rating, and have even laughed at
>>>> the very idea when I have suggested it to them, until I have
>>>> shown them in a component catalogue. I'm willing to bet that
>>>> prior to this exchange, there were more than a few reading what
>>>> Michael said, and doing just that ...
>>>
>>> Well, I have to admit that it (maximum resistor voltage ratings)
>>> doesn't often occur to me, simply because I don't work with HV. But
>>> the person Mr. Terrell responded to above was certainly aware of
>>> why his resistor got blown to smithereens. Hence my annoyance.
>>
>> I see that, but some other less experienced people reading the thread,
>> may well have learnt something from the comment. Still, all sorted now,
>> and everyone's up to speed on resistor voltage ratings !
>
> Well, point taken.
>
> While we're on the subject, where would one get HV resistors, anyhow? Any
> US suppliers?
>
>
> --
I haven't seen any *very* high voltage resistors for some time now in
catalogues, although I expect if you went looking for them, they are still
around from specialist manufacturers. Most that are readily available here
in the UK are rated at up to 400v for some, rather less for others. If I am
replacing a resistor that is going to have a lot of volts across it - for
instance a bleed or voltage sharing resistor across a high voltage cap in a
tube amplifier - I tend to make one up from two half-value resistors in
series. Likewise, when replacing some anode load resistors in 12AX7 or
whatever stages, as these are often 100k connected to a rail of up to 400v,
with the actual anode voltage at the other end, two or even three hundred
volts lower than that. Two 47k resistors rated at 250v each, and connected
in series, ensure that the replacement is up to the job, long term.
Arfa
Michael A. Terrell
David Nebenzahl wrote:
>
> On 1/22/2011 7:56 AM Arfa Daily spake thus:
>
> > "David Nebenzahl" <nob...@but.us.chickens> wrote in message
> > news:4d3a729e$0$15850$8226...@news.adtechcomputers.com...
> >
> >> On 1/21/2011 6:02 PM Arfa Daily spake thus:
> >>>
> >>> Actually, I think that it is quite a useful comment, as in my
> >>> experience in the electronics service business, many techs -
> >>> particularly modern ones - have no understanding that a resistor
> >>> has a maximum working voltage rating, and have even laughed at
> >>> the very idea when I have suggested it to them, until I have
> >>> shown them in a component catalogue. I'm willing to bet that
> >>> prior to this exchange, there were more than a few reading what
> >>> Michael said, and doing just that ...
> >>
> >> Well, I have to admit that it (maximum resistor voltage ratings)
> >> doesn't often occur to me, simply because I don't work with HV. But
> >> the person Mr. Terrell responded to above was certainly aware of
> >> why his resistor got blown to smithereens. Hence my annoyance.
> >
> > I see that, but some other less experienced people reading the thread, may
> > well have learnt something from the comment. Still, all sorted now, and
> > everyone's up to speed on resistor voltage ratings !
>
> Well, point taken.
>
> While we're on the subject, where would one get HV resistors, anyhow?
> Any US suppliers?
http://www.caddock.com/
http://www.ohmite.com/cgi-bin/products.cgi
http://www.ohmcraft.com/resistors/
http://www2.eem.com/ is a database of electronics manufacturers where
you should find more. Several brands I used to use are no longer in
busines or at least under their original names.