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Posted 2010-09-23 20:04:26
I have a 5-year old Daewoo 800-watt microwave oven. It seems to take longer to cook/heat things than it did when it was new.
IIRC I used to heat two cups of water for my coffee in about 5 minutes, but now I need to take 7 or more minutes. (I use filtered tap water, and just for peace of mind, I like the water to boil for at least 60 seconds).
I don't often cook in the microwave, but I thought I used to be able to cook a couple chicken legs and/or thighs in about 8 or 9 minutes. The other night I put in two chicken legs and after 11 minutes, it was still not well done.
Do microwave ovens gradually start wearing out as I seem to be experiencing, or is there something else wrong, like my memory?
Posted 2010-09-23 20:15:14
do you use every time the same cup?
the thiknes of the cup could influence the heating time
look inside the wave
see any black color ?
Posted 2010-09-23 20:58:50
It's possible your incoming power isn't what it used to be. Or....if you're on village power and trying to run an ac, you're microwave will definitely take longer.
Posted 2010-09-23 21:56:06
Suggest you check the power setting of the oven. In some models, power level can be set to 50%, 70% and 100%.
Posted 2010-09-23 22:20:59
I think microwaves ovens do deteriorate over time. I suspect (although I have absolutely no proof) that they wear out because they gradually cook themselves to death. This could occur if the oven was supplying more energy than the food/drink could quickly absorb. That excess energy could conceivably cook the oven's operating components. (?)
OK, slightly O/T, but while you're waiting for the proverbial water to boil, consider how you could use your microwave oven and a block of cheese to calculate the speed of light. It can be done, and with pretty good accuracy
Posted 2010-09-23 22:39:41
I think I'd go with the iffy power supply post, worth checking your supply voltage with and without the oven operating.
All the ones I've had fail have gone off with a nice solid bang
Posted 2010-09-23 23:50:18
I go along with Crossy 100% and know from personal experience how much reduced/reducing power supply affects Microwaves, electric ovens grills, toasters and electric kettle cooking/boiling times.
As Corssy knows (having offered me much kind and helpful info over a period on my power supply issues)I lived through 1 year of iffy reducing power voltages before the PEA finally added an extra power line after 10 months of nicely asking and chasing.
Please Note I live in the Muang district of Khon Kaen City (so it is far from only villages that find power supplies iffy, as the Electricity company keeps hooking up new homes on over worked lines PLUS people's increasing electrical needs(such as Air cons which can really drain voltage on overstretched supply lines)
Posted 2010-09-24 21:14:21
Power output is quite sensitive to the AC input - there is no regulation. A 10% drop in line voltage is likely to reduce microwave power output by more than 20%
Magnetrons, the device that creates the microwaves, like other vacuum tubes, can weaken with age and use. An oven that sees daily use may indeed weaken over the course of several years.
My microwave suffered a drop in power over a period of time until one day it wouldn't heat a thing but before chucking it out I decided to see if it was something other than a dead magnetron. What I found was a dry joint that had developed over some time on the relay contact that controlled power to the magnetron. Resoldering fixed it, but you would need someone who knows microwave oven servicing to check it. If you are of a non-technical nature I wouldn't suggest to anyone to open a microwave unless they're 100% confident of what they are doing as there is around 5 to 7 Kv around the magnetron and there is a capacitor inside charged to lethal voltages.
If in any doubt get a new microwave.
Posted 2010-09-24 22:07:00
My microwave oven is about 15 years old. It definitely has gradually lost "power" over the years (still works though).
Posted 2010-09-24 23:27:39
I don't know for sure, but guessing the 1/2 life of a magnatron is about 100 times that of a single guy in LOS.
Posted 2010-09-25 15:52:34
Oh, my. Such a variety of responses!
I use the same cup every time, I don't want yet another device (kettle) cluttering my small kitchen counter, the power setting (by default) is set to 100%, and haven't a clue how to measure the supply voltage.
Guess I'll just set the old range for 20 minutes per piece of chicken and 40 minutes to boil my coffee water. (just kidding!)
One variable that I did consider was the temp of the water before submitting it for boiling, and even when it's "warm from the tap" (due to the outdoor tank heating up with the daytime sun), it seems to take too long.
Thanks for all the input!
Posted 2010-09-29 01:41:51
Mine totally quit heating one day...found online that a diode can go out. It's near where power cord comes inside and one end grounds to the frame. Amorn shop had the diode replacement 60 baht.... Was an easy fix
careful though like previous posts warned. Deadly voltages to stay away from..
Posted 2010-09-29 07:17:36
No idea about your model.
Years ago in the UK my Microwave 'Brothers' Combi appeared the same, took the cover off and there was 2 heating elements, 1x white the other was black, took it out and went to buy another...... In UK that is a NO NO, sure the shop had one but they would not sell.. can only be fitted by an engineer, must be tested and have an approved stamp etc + cost the earth...
Last year my Panasonic Microwave here also took a lot longer, was the same 1x heating element was black, no problem in buying hear, replaced both while I was at it myself.... must get round to take the cover off again as the light has stopped working
Posted 2010-09-29 08:09:09
I would like to reiterate the warnings about having the back off your microwave.
Several components remain LETHAL even when the unit is off and the plug removed, there are no second chances when dealing with the power levels living inside these units.
Please take care.
Posted 2010-09-29 08:24:45
The problem is almost certainly that you are looking at the microwave while the water is cooking. By the way a 250mil cup should take 2 minutes in most ovens.
I would say they probably do wear out over time. The are actually very high freaeincy radio transmitters tuned to vibrate the water molecules in food. Just as with old radios a slight change in an old capacitator will change the frequency slightly so that it is not optimum.
Posted 2010-09-29 08:36:06
Would add the caution in regard to microwave ovens it is not just the voltage that is a danger but the case is designed to trap the radiation inside the oven and the case is an integral part of the process so must be put back together exactly right to keep it intact. You do not want extra radiation in your kitchen over the long term.
That said I would not let the local TV repair man here do the job either. In this case believe the warnings to leave service to factory trained techs is valid.
Posted 2010-09-30 15:38:48
If you want to check the power output of a microwave oven it can be quite easily done as long as you have a fairly accurate thermometer and a timer. To check do the following;
1. Pour exactly 1000 milliliters (mL) of cool tap water into a microwave-safe container. Using the thermometer, stir the water for about 10 seconds, then measure and record the temperature.
2 Place the container on the center of the oven cooking shelf. DO NOT leave the thermometer in the container. The cooking shelf (tray) or turntable must be in place
3 Heat the water for 62 seconds at full power. Use an accurate digital timer or stop watch if the oven has a mechanical timer.
4 After the heating time is completed, immediately remove the container, stir the water for about 10 seconds, re-measure and record the temperature of the heated water.
5 Subtract the starting water temperature (step 1) from the ending water temperature (step 4) to obtain the temperature rise.
6 To determine the output power in watts, multiply the total temperature rise by a factor of 70.
Starting temperature (T1) = 16.0 deg C<li>Ending temperature (T2) = 33.0 deg C<li>Subtract T1 from T2: 33.0 - 16.0 = 17 (temperature rise)<li>Multiply temperature rise by 70: 17 x 70 = 1190 watts