A few months ago I bought a new Westinghouse WST3501 microwave oven for
our office "eating area".
The oven itself works fine, but we're annoyed by the time of day clock
losing a couple of minutes a day and having to be reset to the correct
time every few days.
I've never seen this happen on several other microwave ovens I've had in
the office or at home, it's like the clock in this one isn't
synchronized to the 60 Hz line. Other line voltage operated clocks in
our office keep the correct time, unless there's a power failure and
they don't have a battery backup in them.
I'm guessing that the electronics in this "made in China" oven were
designed to run on 50 or 60 Hz power, with just a different power
transformer installed in 230 volt models. And, the clock is timed from a
poorly tuned and/or temperature sensitive crystal oscillator, not the
I e-mailed Westinghouse about this but they put me off to "Fox
International" who thusfar hasn't answered my e-mail about it.
Not an earth shaking problem by any means, but my curious mind wants to
know what's really going on with the clock function in that oven.
I'd just as soon put a pice of tape over the readout and fughedit, but I
can't do that because it's needed for the cooking functions too.<G>.
There could be a jumper on the control board to set 50 or 60 cycle power
as a time base. I've seen new equipment arrive with the wrong country
power plug installed. Products manufactured for the Southern Hemisphere
need electrons that spin in the opposite direction to work properly. You
may be able to obtain an electron spin converter if that's the problem.
I actually thought about a jumper, but if there is one and it's set for
50 Hz operation that damn clock would gain 12 minutes PER HOUR, which
thank G_d it isn't.
Re the spin converter, is it based on something like this?
Back when I was in the Hippies about four decades ago, girls were not
getting tattoos like today, it wasn't a common sight. A guy might get
one earring like a pirate but not the body piercings that are common
in this century. Tattoos didn't become a fad until all the movie and
pop music stars started all that nonsense. I wonder what the children
of the extreme body modification crowd are going to do to shock their
physically modified parents? Perhaps the little tykes will become
extreme, button down, super religious, Republican Conservatives? 8-)
Oh. Here's some more you might find useful:
You're circling the drain,
They gonna be drawin' you in chalk on the sidewalk,
Gave me the stink-eye
He needs flashlight therapy
'Roided up primate
Hold a grudge longer than my ex-wife
The medicine man's gonna be wavin' chicken claws over your ashes
And, when referring to a suspect, the following have been found to be
appropriate: Goblin, Gremlin, Squint, Slope, Miscreant, Do-bad, Slop-sucker,
Solid waste, and Chicken-plucker.
When you exhaust this set, just let me know. I've got a million of 'em.
Could be, but unlikely. The typical mass produced (and cheapest)
plug-in timers use circuits that count line frequency.
connected to 60 Hz AC, I would expect the clock to run fast, not slow.
So the slow clock is not likely to be related to a wrongly placed jumper
or the use of a circuit designed for a 50 Hz supply.
I've had a chronic problem of the opposite kind in my house. Most but
not all of my digital clocks run a few seconds/day fast. I see this
with 1 of my 3 clock radios, both VCRs, my DVR, and the clock I've had
on every microwave (3 of them in about 20 years). There seems to be no
pattern to which home circuit the devices are connected to (happens to
devices connected to either 120V arm of my 240V service). Some of the
devices are 15+ years old, some are much more recent. Some are dual
voltage, some are 120V 60 Hz only. I convinced my electric power
company to come out and run diagnostics. They found absolutely nominal
readings with no evidence of voltage spikes, frequency deviations, RFI
or EMI. The engineer said he had been doing diagnostic work for the
same company for more than 10 years and no other customer has ever had a
similar complaint. I've resigned myself to making it a routine to reset
the time on all of these inaccurate devices at the beginning of each
I hope the problem is restricted to my clocks. I'd hate to think that
something in this environment is also causing my biologic clock to run
fast and causing a shortened life expectancy :-) .
Give me back the old fashioned mechanical hysteresis motors! They never
ran fast or slow. They kept my old tube clock radios running accurately
for decades. I've got only one motor driven clock left, the one built
into my wall oven. Except for my "atomic" desk clock and "atomic" wrist
watch, that oven clock keeps the most accurate time in our house.
using the power line for timing some process.
The question was raised of the accuracy of the line frequency. I got in
touch with a guy in Boston Edison' engineering office.
At that time IIRC the tolerance on the frequency was 1/10 of a cycle. He
pointed out that the root cause of the great Northeast blackout of 1964 was
caused not by a short circuit somewhere but by some undue surges on the
grid so that various generators got out of sync. That precipitated the
generators going off line to protect themselves. You readers who have ever
had a rotating machinery lab and tried to merge two generators together will
recall the caveats of throwing the switch before the two units were in
As another tidbit of our conversation was that the generating facility ran a
standard electric clock of their lines. At about midnight the task was to
slowly bring the clock to agree with the WWV time signal. The customer was
thus assured that they got all the cycles they were paying for.
There fore the best time to set your clock was about 3 am.
I am sure a lot has changed since then what with cesium clocks etc.
Somehow those days were more fun.
working as a DJ at radio station in McAlester, Oklahoma. When they had
the big power black out in the North East their electric clock lost
several minutes of time. So they reset it. Then for a couple of weeks
they had to reset it every day, because it gained time, as the power
companies corrected the power line frequency to bring it back into sync
with the WWV time. The power line frequency is very stable over long
periods. As somebody said up thread the old fashioned electric clock
was extremely accurate over years. The power line frequency over short
periods is not particularly good, but over the long run it is about as
stable as you can get.
On Tue, 19 Oct 2010 14:48:13 -0400, jeff_wisnia wrote:
that'd drift by a factor of 5/6, though.
Interesting fault. I wondered if the clock was on its own oscillator and
is supposed to do a periodic resync against the line frequency (once a
day, say), with the "resync" part busted on yours - but I'm not sure that
makes sense either, because surely the clock would see 0 line pulses all
the time and reset itself to some default time each resync (unless the on-
board smarts say something like "there's obviously a fault with the pulse-
counter, I'll ignore it").
Bad parts, maybe. Perhaps someone goofed and a batch got made with the
wrong frequency crystal oscillator. Not sure if the manufacturer would
ever own up to that, though.
Some IC's have a built in clock that requires an external capacitor to
function. There is a probability of less than accurate cap values being
the culprit. Another thing that someone else posted on about problems
with his clocks and having tests done looking for interference coming
from the AC power. I know that transformers for office buildings had to
be redesigned after problems were discovered when the age of the
personal computer came along. All the switching power supplies were
causing overheating due to the asymmetrical loads put on the
transformers. I came across a simple power supply circuit that puts out
a clock signal from the 60Hz power. I understand that this design used
as a time base for a clock is susceptible to line noise.
The cheapness of many consumer electronics items today leads me to
believe that best practices are not being used in the design of the
circuitry. In an office environment there have got to be all kinds
of harmonics flooding the AC power system. If any of you guys are
like me, you notice things are off and not quite right with things
and can't stand it. I'll be out on a service call somewhere and
notice a loose screw on the door handle and I pull a screwdriver
out of my pocket to tighten up the errant screw. I once notified a
business owner that the toilet in the men's room was leaking and
he should call a plumber to fix it, he didn't think it was important
until he got a thousand dollar water bill. I like things to work
right and find conquering misbehaving systems to be a fun challenge.
Now if I could only figure out a way to repair women. 8-)
If you don't break them, they don't need to be repaired. The key to
successful relationships with women who are important to you is to let
them have their way - or if you are really skillful, convincing them
that they are having their way even if you know better (also known as
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