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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Can a microwave oven have its output imited?
Can a microwave oven have its output controlled, limited, by something
like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. Is there any chance I can turn the full power down by 10%, for every use? (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. The old no-name-brand only had one other power level, Defrost, but it made the same noise all the time, and to see how much of the time it was making heat, I had to turn on a nearby AM radio and tune to a weak or no station, and listen to the radiation from the microwave.) |
#2
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Can a microwave oven have its output imited?
On Sat, 14 May 2011 14:35:51 -0400, mm
wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. Is there any chance I can turn the full power down by 10%, for every use? (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. The old no-name-brand only had one other power level, Defrost, but it made the same noise all the time, and to see how much of the time it was making heat, I had to turn on a nearby AM radio and tune to a weak or no station, and listen to the radiation from the microwave.) The "power control" is a "per cent on" control. 90% for one minute means the unit runs at full power for .9 * 60 seconds or 54 seconds, usually in semi-equal segments such as on 18 seconds, off 2 seconds or on 9 seconds, off 1 second. John |
#3
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Can a microwave oven have its output imited?
mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. Is there any chance I can turn the full power down by 10%, for every use? Can you write code for the microprocessor in the control panel? The power function is hard coded into the controller. (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. That is a form of 'Pulse Width Modulation'. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#4
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Can a microwave oven have its output imited?
On Sat, 14 May 2011 16:35:53 -0400, "Michael A. Terrell"
wrote: mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. I can see how this is ambiguous. Is there any chance I can turn the full power down by 10%, for every use? Can you write code for the microprocessor in the control panel? The No. power function is hard coded into the controller. I didn't have in mind changing the power function, but changing the circuit that makes the microwaves. Maybe at the stage at or just before the microwave tube. So they would be weaker. By changing the bias on the output transistor, or something like that. I was hoping there might be a pot there already. The power function would still work, turning the radiation on X% of the time and off 100-X% of the time. (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. That is a form of 'Pulse Width Modulation'. Good to know. Thanks. |
#5
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Can a microwave oven have its output imited?
mm wrote: On Sat, 14 May 2011 16:35:53 -0400, "Michael A. Terrell" wrote: mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. I can see how this is ambiguous. Is there any chance I can turn the full power down by 10%, for every use? Can you write code for the microprocessor in the control panel? The No. power function is hard coded into the controller. I didn't have in mind changing the power function, but changing the circuit that makes the microwaves. Maybe at the stage at or just before the microwave tube. So they would be weaker. By changing the bias on the output transistor, or something like that. I was hoping there might be a pot there already. Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. The power function would still work, turning the radiation on X% of the time and off 100-X% of the time. (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. That is a form of 'Pulse Width Modulation'. Good to know. Thanks. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#6
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Can a microwave oven have its output imited?
On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell"
wrote: mm wrote: On Sat, 14 May 2011 16:35:53 -0400, "Michael A. Terrell" wrote: mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. I can see how this is ambiguous. Is there any chance I can turn the full power down by 10%, for every use? Can you write code for the microprocessor in the control panel? The No. power function is hard coded into the controller. I didn't have in mind changing the power function, but changing the circuit that makes the microwaves. Maybe at the stage at or just before the microwave tube. So they would be weaker. By changing the bias on the output transistor, or something like that. I was hoping there might be a pot there already. Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do. Thanks again. The power function would still work, turning the radiation on X% of the time and off 100-X% of the time. (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. That is a form of 'Pulse Width Modulation'. Good to know. Thanks. |
#7
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Can a microwave oven have its output imited?
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#8
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Can a microwave oven have its output imited?
mm wrote: On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell" wrote: Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do. Thanks again. You're welcome. That's why I have two microwave ovens. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#9
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Can a microwave oven have its output imited?
On May 14, 8:49*pm, "Michael A. Terrell"
wrote: mm wrote: On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell" wrote: * Magnetrons don't work that way. *They run at full power over their useful life. *That's why they have to use PWM to control the average power level. Makes sense. *Okay. *I'll give up the plan. *That's one more thiing I don't have to do. Thanks again. * *You're welcome. *That's why I have two microwave ovens. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. I use two. A big sears 800 watts, and little Panasonic inverter 1200 watts. Weird but true. Always use the inverter for frozen dinners. I think you have to wide pulse the magnetron, like many seconds. A little weird, the inverter takes about 3 seconds to fire up after pushing start. Greg |
#10
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Can a microwave oven have its output imited?
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#11
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Can a microwave oven have its output imited?
GS wrote: On May 14, 8:49 pm, "Michael A. Terrell" wrote: mm wrote: On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell" wrote: Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do. Thanks again. You're welcome. That's why I have two microwave ovens. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. I use two. A big sears 800 watts, and little Panasonic inverter 1200 watts. Weird but true. Always use the inverter for frozen dinners. I think you have to wide pulse the magnetron, like many seconds. A little weird, the inverter takes about 3 seconds to fire up after pushing start. The Magnatron filament is turned on and off to pulse the output. It takes a fraction of a second to warm up. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#12
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Can a microwave oven have its output imited?
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#13
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Can a microwave oven have its output imited?
On May 15, 5:37*pm, "Michael A. Terrell"
wrote: mike wrote: wrote: On Sat, 14 May 2011 14:35:51 -0400, mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? * Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. *(So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. |
#14
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Can a microwave oven have its output imited?
On May 14, 11:35*am, mm wrote:
Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? * Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. *(So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. Take it back and buy one that puts out the power level your recipes call for. But bewa we have an 800 watt oven that used to be compatible with recipes, but now all the recipes are for 1100 watts. |
#15
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Can a microwave oven have its output imited?
klem kedidelhopper wrote: On May 15, 5:37 pm, "Michael A. Terrell" wrote: mike wrote: wrote: On Sat, 14 May 2011 14:35:51 -0400, mm wrote: Can a microwave oven have its output controlled, limited, by something like adjusting the AGC on a TV? Or on combo devices, radio, cassette, CD, tv, there is usually a pot on each of those, adjusted so the volume stays the same when one changes functions. I didn't like my old small microwave oven because it was so small, and I also had to cook longer than instructions said, because it was low power. (So I was in the habit of mulitplying the time given by 1.1 or 1.3, but I was hoping not to have to do that anymore.) Now I have a new, one-year old, full-size Sharp microwave -- I can provide the model number if it matters -- and it is too powerful. Things cooked in their packages according to instructions have their water boiling over and taking some of the food with it, and I presume other food is being cooked more than instructions or recipes call for. It has a power control that will lower the power by 10% for every push of the button, but I would have to use that button every time. Is there any chance I can turn the full power down by 10%, for every use? (As an aside, it's interesting that on 90% power, for example, I can tell when the microwave part is functioning because it makes more noise during the 90% than the 10% of the time. The old no-name-brand only had one other power level, Defrost, but it made the same noise all the time, and to see how much of the time it was making heat, I had to turn on a nearby AM radio and tune to a weak or no station, and listen to the radiation from the microwave.) The "power control" is a "per cent on" control. 90% for one minute means the unit runs at full power for .9 * 60 seconds or 54 seconds, usually in semi-equal segments such as on 18 seconds, off 2 seconds or on 9 seconds, off 1 second. John I've got the same problem, but need more like 50%. I'd considered adding another cap at half the value. Not sure how to to the HV switching safely with affordable components. Just program the cook power, or get a smaller oven. The power supply in a microwave can kill you in a heartbeat. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. I was just reading this thread and it brought a question to mind. What if theoretically speaking you dropped the line voltage to the HV circuit but not the control section? This would reduce both the filament voltage as well as the HV secondary voltage on the transformer. The result I would think would be a reduction in output power, wouldn't it? Lenny It will stop oscillating, if you reduce them very much. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#17
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Can a microwave oven have its output imited?
Michael A. Terrell wrote:
GS wrote: On May 14, 8:49 pm, "Michael A. Terrell" wrote: mm wrote: On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell" wrote: Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do. Thanks again. You're welcome. That's why I have two microwave ovens. -- You can't fix stupid. You can't even put a Band-Aid? on it, because it's Teflon coated. I use two. A big sears 800 watts, and little Panasonic inverter 1200 watts. Weird but true. Always use the inverter for frozen dinners. I think you have to wide pulse the magnetron, like many seconds. A little weird, the inverter takes about 3 seconds to fire up after pushing start. The Magnatron filament is turned on and off to pulse the output. It takes a fraction of a second to warm up. Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. |
#18
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Can a microwave oven have its output imited?
Cydrome Leader wrote in
: Michael A. Terrell wrote: GS wrote: On May 14, 8:49 pm, "Michael A. Terrell" wrote: mm wrote: On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell" wrote: Magnetrons don't work that way. They run at full power over their useful life. That's why they have to use PWM to control the average power level. actually,like any other vacuum tube,power output depends on plate voltage and current. If you lower the plate voltage,the magnetron WILL produce less power. that's how the inverter ovens work. But originally,it was too expensive to control plate voltage,so the manufacturers went for duty cycle operation instead.("pulsed") You can do that with a cheap relay and timer circuit. Now,it's cheaper to use an inverter because the heavy iron transformer costs so much more than a smaller HF switcher transformer,and a switcher can control it's output voltage. Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do. Thanks again. You're welcome. That's why I have two microwave ovens. -- You can't fix stupid. You can't even put a Band-Aid? on it, because it's Teflon coated. I use two. A big sears 800 watts, and little Panasonic inverter 1200 watts. Weird but true. Always use the inverter for frozen dinners. I think you have to wide pulse the magnetron, like many seconds. A little weird, the inverter takes about 3 seconds to fire up after pushing start. The Magnatron filament is turned on and off to pulse the output. It takes a fraction of a second to warm up. Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. it's cheaper to switch the transformer side instead of the HV side,and the HV switching probably wears out quicker. -- Jim Yanik jyanik at localnet dot com |
#19
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Can a microwave oven have its output imited?
Some of the older US made units from Litton or Tappan had
a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. |
#20
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Can a microwave oven have its output imited?
William Sommerwerck wrote:
Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. I really liked those older machines. They were easy to use. I still don't get why a microwave oven needs multiple buttons pressed to heat food. It used to just be, turn the timing knob and press start. That's it. |
#21
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Can a microwave oven have its output imited?
"Cydrome Leader" wrote in message
... William Sommerwerck wrote: I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). I really liked those older machines. They were easy to use. I still don't get why a microwave oven needs multiple buttons pressed to heat food. It used to just be, turn the timing knob and press start. That's it. My GE has six instant-start buttons, for one through six minutes. |
#22
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Can a microwave oven have its output imited?
William Sommerwerck wrote: "Cydrome Leader" wrote in message ... William Sommerwerck wrote: I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). I really liked those older machines. They were easy to use. I still don't get why a microwave oven needs multiple buttons pressed to heat food. It used to just be, turn the timing knob and press start. That's it. My GE has six instant-start buttons, for one through six minutes. Mine cycles over 10 seconds. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#23
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Can a microwave oven have its output imited?
William Sommerwerck wrote:
"Cydrome Leader" wrote in message ... William Sommerwerck wrote: I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). If you like switching a kilowatt sized transformer on and off every second, power to you. Same for a reed relay rated at kV at hundreds of mA. It would obviously be easier with one of those switching power supply microwaves, but that's not how the old microwaves worked. |
#24
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Can a microwave oven have its output imited?
"Cydrome Leader" wrote in message
... William Sommerwerck wrote: What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). If you like switching a kilowatt sized transformer on and off every second, power to you. Same for a reed relay rated at kV at hundreds of mA. It would obviously be easier with one of those switching power supply microwaves, but that's not how the old microwaves worked. As far as I know, my 10-year-old GE is a "newer" model. This has become one of those "inquiring minds want to know" questions. There are leakage meters, which would show changes in level. Does anyone make a power meter you can place in the cavity? |
#25
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Can a microwave oven have its output imited?
William Sommerwerck wrote:
"Cydrome Leader" wrote in message ... William Sommerwerck wrote: What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). If you like switching a kilowatt sized transformer on and off every second, power to you. Same for a reed relay rated at kV at hundreds of mA. It would obviously be easier with one of those switching power supply microwaves, but that's not how the old microwaves worked. As far as I know, my 10-year-old GE is a "newer" model. This has become one of those "inquiring minds want to know" questions. There are leakage meters, which would show changes in level. Does anyone make a power meter you can place in the cavity? You might get by with a cup of water and a light bulb. Neon lights with the leads twisted together was the standard "indicator" for microwaves when I last touched these things. You really want the cup of water as a dummy load when putting weird stuff in a microwave. I just ran at test like that on my made in 1981 samsung microwave. It surprisingly has a digital clock and numeric keypad- space age stuff for the time. This thing was clearly made when they were terrified of microwave leaks. There are a whopping 20 torx screws alone holding the glass in the front door, plus more holding the door together. Anyways, in defrost mode, the magnetron is clearly cycled on and off in 15 second intervals. I could tell when it was on from when the small lightbulb lit up. |
#26
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Can a microwave oven have its output imited?
William Sommerwerck wrote: "Cydrome Leader" wrote in message ... William Sommerwerck wrote: What do you mean by excessive? If a magnetron can be modulated by varying its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO NOT want the magnetron running at full power for "long" periods, followed by even longer periods off (eg, one minute, four minutes off, for 20%). If you like switching a kilowatt sized transformer on and off every second, power to you. Same for a reed relay rated at kV at hundreds of mA. It would obviously be easier with one of those switching power supply microwaves, but that's not how the old microwaves worked. As far as I know, my 10-year-old GE is a "newer" model. This has become one of those "inquiring minds want to know" questions. There are leakage meters, which would show changes in level. Does anyone make a power meter you can place in the cavity? Connect a voltmeter across the power line. You will see the voltage change as the oven switched between a couple Watts to 700-1100 Watts. I can hear a change in the hum from the HV transformer on my oven. -- You can't fix stupid. You can't even put a Band-Aid™ on it, because it's Teflon coated. |
#27
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Can a microwave oven have its output imited?
Cydrome Leader wrote in
: William Sommerwerck wrote: Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. No,it's longer than that. probably a minimum of ~10 seconds. you can tell by the change in sound of the oven,the magnetron loads more when it's cooking. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. I really liked those older machines. They were easy to use. I still don't get why a microwave oven needs multiple buttons pressed to heat food. It used to just be, turn the timing knob and press start. That's it. Maybe it's cheaper to use a digital timer than a mechanical timer. Although ISTR seeing some low-end MW ovens that still had the mech.timer. But people want the flexibility of using their MW for more than simple reheating/cooking tasks. My GE has all sorts of functions I never use,mostly sensor cooking. -- Jim Yanik jyanik at localnet dot com |
#28
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Can a microwave oven have its output imited?
"Jim Yanik" wrote in message
4... 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. The problem -- as I've repeatedly stated -- is that if the "on" part of the variable-power cycle is more than a few seconds -- possibly as short as 5 seconds, and /definitely/ 10 -- you're going to have localized boiling. I occasionally see the oven's lights changing brightness, and hearing various "cycling" noises. I'm going to have to check into this... |
#29
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Can a microwave oven have its output imited?
On May 17, 11:27*am, Jim Yanik wrote:
Cydrome Leader wrote : William Sommerwerck wrote: Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. No,it's longer than that. probably a minimum of ~10 seconds. you can tell by the change in sound of the oven,the magnetron loads more when it's cooking. 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. I really liked those older machines. They were easy to use. I still don't get why a microwave oven needs multiple buttons pressed to heat food. It used to just be, turn the timing knob and press start. That's it. Maybe it's cheaper to use a digital timer than a mechanical timer. Although ISTR seeing some low-end MW ovens that still had the mech.timer. But people want the flexibility of using their MW for more than simple reheating/cooking tasks. My GE has all sorts of functions I never use,mostly sensor cooking. -- Jim Yanik jyanik at localnet dot com I started using my combo oven turbo/microwave and I was disappointed it only had 15 second increments. Later I found out Turing the dial while it's cookin, you can reset the time in fin increments which is really neat, without having to stop and start. In one case I replaced a digital timer with a mechanical timer, which both me and dad really liked. It was just like the old heath kit oven. Greg |
#30
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Can a microwave oven have its output imited?
On May 17, 11:10*am, "William Sommerwerck"
wrote: "Jim Yanik" wrote in message 4... 1 second seems pretty excessive. I don't recall what the timing cycle on the Tappan ones were, but it was less than a minute for sure, but not every few seconds. The problem -- as I've repeatedly stated -- is that if the "on" part of the variable-power cycle is more than a few seconds -- possibly as short as 5 seconds, and /definitely/ 10 -- you're going to have localized boiling. I occasionally see the oven's lights changing brightness, and hearing various "cycling" noises. I'm going to have to check into this... Our Panasonic cycles in the 5 - 15 second range. |
#31
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Can a microwave oven have its output imited?
William Sommerwerck wrote:
Some of the older US made units from Litton or Tappan had a giant reed relay, and the HV was actually switched on and off for the defrost mode. They made a nice sound switching on and off. I'm curious as to how my GE works. If, at 50% (say) you were full "on" for one minute, then off for one minute, you'd be running in that first minute at a power level that would cause localized boiling. (This is a problem with soups and oatmeal.) I do not see that. Therefore, I have (???) to assume that PWM with a cycle of less than one second is used. There are a few things you can do. Use containers with straight vertical sides. The thinnest part of the material boils first in a typical bowl. I've been acquiring HUGE ceramic coffee mugs to cook soup. The other thing you can do is siphon off the energy with a cup of water. Varying the amount of water and the power cycling can accommodate most needs. In some cases, a microwave browning dish can average the long-duration PWM of the oven. I've done some experiments with a dish that looks like a lemon juicer. The donut shape of the liquid gets energy from all sides and can help moderate the edge boiling. You'd really not want any thickness of the subject material to be any thicker than the microwaves can penetrate. |
#32
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Can a microwave oven have its output imited?
"mike" wrote in message
... There are a few things you can do. Use containers with straight vertical sides. The thinnest part of the material boils [???] first in a typical bowl. I've been acquiring HUGE ceramic coffee mugs to cook soup. I use huge ceramic cereal bowls. Heating soup or oatmeal at full power still causes localized boiling. The other thing you can do is siphon off the energy with a cup of water. Varying the amount of water and the power cycling can accommodate most needs. With my oven, simply lowering the power does the trick. A big bowl of oatmeal cooks in 6 minutes at 50% power, with no boilover. I've done some experiments with a dish that looks like a lemon juicer. The donut shape of the liquid gets energy from all sides and can help moderate the edge boiling. You'd really not want any thickness of the subject material to be any thicker than the microwaves can penetrate. It seems to me that's exactly what you want. |
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Can a microwave oven have its output imited?
Percent power may not be related to actual duty cycle. 50% is not 50%
on and 50% off. The ON time may be longer based on service info for a Sharp Microwave, It takes time for the filament to warm up and there may be reduced or no output. This is taken into account. |
#34
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Can a microwave oven have its output imited?
"Ron D." wrote: Percent power may not be related to actual duty cycle. 50% is not 50% on and 50% off. The ON time may be longer based on service info for a Sharp Microwave, It takes time for the filament to warm up and there may be reduced or no output. This is taken into account. Which still results in a 50% on to off output from the Magnetron. Just how long do you think it takes for the filament to reach full operating temperature? We aren't talking about 12 volt tubes with 150 mA filaments that take ten seconds to warm up. -- It's easy to think outside the box, when you have a cutting torch. |
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