[TheForge] Microwave Question OT

Tue Feb 17 17:30:05 2004

Standard resistors have very low Voltage ratings.  For example, a RCR07
resistor has only a 250 Volt rating. =20

Also, if the resistor breaks, if it doesn't discharge, you are fried.

However, we do use resistors in our automatic chickenstick circuits for =
that
exact reason.  And, it's easier on the capacitors in the circuit also.

-----Original Message-----
From: [email protected] =
[mailto:[email protected]]
On Behalf Of Darrell
Sent: Tuesday, February 17, 2004 4:17 PM
To: [email protected]
Subject: Re: [TheForge] Microwave Question OT

A 10K ohm 10 Watt resistor in the ground lead on the chicken stick will
eliminate the big pop and only add a couple of seconds to the discharge
time. Darrell

http://www.machinemaster.com
----- Original Message -----=20
From: "David E. Smucker" <[email protected]>
To: <[email protected]>
Sent: Tuesday, February 17, 2004 11:10 AM
Subject: Re: [TheForge] Microwave Question OT

> Grover -- thanks for the information.
> First I understand about the half wave rectifier -- and that explains=20
> the hum at the breaker panel. Think I will just swap out the breaker=20
> because that is very easy for me to do.  (32 years of industrial=20
> construction experience -- and I wired this
new
> house and the new  shop.)  That is also why I know there is nothing=20
> else
on
> this breaker.  That being said -- I think it is more likely that it is =

> a microwave capacitor that is going bad.  It is just a lot easier to=20
> swap
the
> breaker first.  My industrial trouble shooting says that unless you=20
> are
damn
> sure of a cause -- do the easy one first before you do the brain=20
> surgery.
>
> The clunk is right at the very start -- and that is also when the=20
> breaker trips.  I can hear the fan start, and the softer hum of the=20
> transformer
and
> then hear the louder hum as the  magnetron filaments have warmed up. =20
> Yes, this seem to be a loud hum.  What doesn't seem to make sense to =20
> me is why it only does it sometimes?  The only time it will trip=20
> except at the very start is when using it to "defrost" and I have only =

> seen this once or
twice
> and it was when the magnetron was cycled back on.  We are the type of
folks
> that mostly use the microwave to heat up coffee or tea, heat leftovers =

> and defrost things.  We very seldom use the mid range settings that=20
> cycle to give a lower average output the way the defrost does.
>
> Thanks for the warning about the chicken stick -- just like going into =

> the high voltage section in the days when we used to work on TV's.  (I =

> never worked on TV's but my Dad did a lot in the good old vacuum tube=20
> days of
the
> 50's and 60's.)  Always good to know that your capacitor has been=20
> discharged.  Oh and for what it is worth Dad always called them=20
> condensers -- that is the way he learned it in school.  He was an EE,=20
> 1933 University of Illinois.
>
> Again Thanks and work safe,
>
> Dave Smucker
> ----- Original Message -----
> From: "Grover Richardson" <[email protected]>
> To: <[email protected]>
> Sent: Tuesday, February 17, 2004 10:13 AM
> Subject: RE: [TheForge] Microwave Question OT
>
>
> Hi there.  Just got to email.
>
> Well, microwave ovens have a fuse inside, under the cover. If that=20
> fuse isn't blowing, the oven likely is ok.
>
> A microwave oven is a half wave rectifier.  So, it AVERAGES 13.6 Amps, =

> but actually it's one half cycle of nothing, and one half cycle of=20
> 27.2 Amps. So, the breaker could be going soft, or there might be=20
> other items on the breaker that are adding up the current.
>
> An easy thing to do, would be to swap that breaker with another one of =

> the same rating to see if it's the breaker, and at no cost.  This is=20
> if you
know
> electrical panels sufficiently well to not fry yourself, or know=20
> someone
to
> do it for you.
>
> Now, having said that. Your description tells more.
>
> If it clunks exactly when you start, then there is a good possibility=20
> that the capacitor is going bad.  Does the oven hum loudly?  This=20
> would also indicate a soft capacitor.  Normally when you turn one on,=20
> you have the
fan
> cut on, and you get a small hum from the transformer.  Then, in about=20
> 2 seconds, when the magnetron filaments have warmed up, you will hear=20
> the
fan
> slow down and the transformer hum get louder.
>
> Built ins can be difficult to work on (only worked on 2, and they both
were
> boogers<G>).
>
> If you can get the front off, I can tell you more on troubleshooting.
>
> DANGER WILL ROBINSON.  You will need what we call a "chicken stick." =20
> This is a screwdriver with a ground wire attached.  This way you can=20
> ground everything you are about to touch, before you touch it.
>
>
> -----Original Message-----
> From: [email protected]
[mailto:[email protected]]
> On Behalf Of David E. Smucker
> Sent: Monday, February 16, 2004 3:43 PM
> To: [email protected]
> Subject: [TheForge] Microwave Question OT
>
>
> Grover -- this is not about the heavy metal session OT but about my=20
> home microwave.
>
> It is new, less than a year old, rated at 1100 watts, max current 13.6 =

> --
> yet we are having trouble with it knocking out the breaker  rather =
often.
It
> is on a 20 amp breaker, no. 12 wire, with nothing else on that breaker =

> so
it
> should not trip.  I have not yet changed out the break to see if it is
going
> bad but it was new too -- same age as the microwave.  (new house)
>
> It does not always trip -- maybe every 10 to 15 times it is started. =20
> Also the microwave kind of "clunks" when starting?  can the magnetron=20
> be loose? Also I get a heavy hum (60 hertz) at the breaker when=20
> starting.
>
> I know I can change out the breaker, and also open up the microwave to =

> see it something is loose but it is a build-in and so far I have been=20
> too lazy to do either.
>
> Just wondering if you ever ran into this.
>
> Dave Smucker
> ----- Original Message -----
> From: "Grover Richardson" <[email protected]>
> To: <[email protected]>
> Sent: Monday, February 16, 2004 10:14 AM
> Subject: RE: [TheForge] microwave heavy metal session OT somewhat
>
> SNIP
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