how is it possible?

About 3 years ago, I bought a new Frigidaire microwave, and of course it has a digital clock on it. This crazy clock gains approximately a minute every 2 months. Our stove right below it has a digital clock also, it keeps perfect time. It's just maddening to look at both of them, and the time is always different. In this day and age, how is it possible that a digital clock cannot keep time? just crazy
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nefletch wrote:

It can happen if clock component was a cheap origin.
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Somewhere buried in a junk drawer in my house is a cheap digital timer my daughter bought a few years ago. It's alarm is apparently set and when it's very, very quiet in the house (rarely!) I can hear it give off a single beep between 9 and 9:30 PM.
That beep has slowly been "advancing" though the hour and is now about 20 minutes ahead of where it used to be. If it wasn't kind of humorous, I'd spend some time looking for it and throw it away.
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easy; internal crystal-controlled clock,and temperature variations change it's clock rate. and they often are not calibrated properly right from the factory.
just imagine how the guy in a clock store feels. ;-)
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Jim Yanik
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nefletch wrote:

Hummmm looks like you need an inline frequency changer .... shouldn't take to much depending on how you want to do it... I'd convert to 50 cycles and bump it back up 59.93 for a starting point. http://www.behlman.com/products.htm
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On 11/16/2011 1:05 PM, nefletch wrote:

really a huge change, compared to many digital watches I have owned. It could be better, but isn't really bad. The biggest problem is that you have one on stove that is probably synchronized with the power line frequency. The power line frequency is (or has been until recently) very accurately controlled so that the stove clock keeps better time than the average quartz clock. Of course the stove clock may need to be reset after a power outage.
Bill
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On 11/17/2011 8:18 AM, Bill Gill wrote:

I would also think appliances, like microwaves and stoves, would sync to the power line frequency, which has a good long term stability. If the power line frequency average was off both the microwave and stove should be off together. Might be interesting to use something like the clock in a cell phone (which I presume is set by the cell provider and is high accuracy) to see which clock is drifting (might be the stove).
Wouldn't think either clock would use a crystal oscillator, as in Jim's post, but that would explain drift that shouldn't happen with power freq sync. May be the best guess.
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bud-- wrote:

I bought an inexpensive GE microwave oven for the office a year or so and the clock gains about a minute a day.
My suspicion is that they didn't sync to the line frequency because the same circuit board is probably used in the microwave ovens they sell in other parts of the world whare the line frequency is 50 Hz. They prolly use a cheap piezo or xtal oscillator which can't stay right on frequency forever and just change the power xformer to one which accepts a 220 vac line.
Jeff
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wrote:

Also that microwave oven needs a crystal anyway because it has a microprocessor of some kind in it to run it. That needs an oscillator to generate the clock signal that runs it. So, by choosing the frequency for the microprocessor and then dividing that down, they can get the source for the time of day clock for free. How many do that versus use the line frequency as a more accurate source, I don't know. I do know that in the various appliances I have I don't notice any significant drift. I only reset them for daylight savings twice a year or when the power is interrupted.
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nefletch wrote:

Yet another use for duct tape.
Is there anything duct tape cannot fix?
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Red Green wrote:

I agree. Stating the obvious is often silly, but it's a good rhetorical device to separate the wheat from the trees.
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nefletch wrote:

Is it possible the clock of the stove below gets its timing from the 60 Hz AC line while the Frigidaire microwave instead uses its own quartz crystal? 60 Hz AC is usually more accurate than any crystal, but sometimes unplugging the device from the AC for several minutes will help, and I've seen it help with PC motherboards and clock cards that were running wild and gaining or losing a few minutes a day. Sometimes changing crystal (thin 1/4" long silver colored cylinder) is the only solution, and I've found that crystals taken from $1 watches always work, but I've had a few crystals from electronics supplies that didn't.
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