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
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.
internal crystal-controlled clock,and temperature variations change it's
and they often are not calibrated properly right from the factory.
just imagine how the guy in a clock store feels. ;-)
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
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
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.
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
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.
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
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