sci.electronics.repair@googlegroups.com

Today's topics:

* Whirlpool RF0100 electric stove trips breaker. - 3 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/88c59b94b9023959?hl=en
* Sometimes, a sledge - hammer is the right tool ... :-) - 2 messages, 2
authors
http://groups.google.com/group/sci.electronics.repair/t/2bc7695b4fb03244?hl=en
* Popularity of the small and medium-size Adidas Porsche Design - 1 messages,
1 author
http://groups.google.com/group/sci.electronics.repair/t/aff5e6c77b3dfa0e?hl=en
* Good LED TV repair men in San Diego County area? - 1 messages, 1 author
http://groups.google.com/group/sci.electronics.repair/t/4ed1121fdbf133bb?hl=en
* Testing SMPS - 2 messages, 2 authors
http://groups.google.com/group/sci.electronics.repair/t/1cc72f0926af56cc?hl=en

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TOPIC: Whirlpool RF0100 electric stove trips breaker.
http://groups.google.com/group/sci.electronics.repair/t/88c59b94b9023959?hl=en
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== 1 of 3 ==
Date: Thurs, Oct 21 2010 5:06 pm
From: "David Farber"

>
> "David Farber" <farberbear.unspam@aol.com> wrote in message
> news:i9och8$tn3$1@news.eternal-september.org...

>> This Whirlpool electric stove, model number RF0100, appears to be an
>> older model. If you were wondering what blasted the ground lead of my
>> Kill-A-Watt
>> meter which I posted about two days ago in the thread about the
>> Phillips security screw, this is the culprit. The schematic is here:
>> http://members.dslextreme.com/users/farberbear/Repair/Electric-stove.jpg
>> as
>> I photographed it from the back of the stove.
>>
>> I used to have the stove hooked up to a 240 volt circuit as
>> indicated in the
>> schematic and it worked ok. But, now I don't have a 240V line. Or at
>> least not yet. I was trying to at least get it to work on 120V
>> because only the oven will be used and at very low heat, probably
>> around 200 degrees to cook
>> some ceramics. The stovetop and broiler wires have been disconnected
>> because
>> they are not needed. This particular model does not have a light or a
>> clock
>> as shown in the schematic. I wired it so that L1 went to hot
>> (black), L2 went to N (white), and N to ground (green). The load
>> across the electric plug, hot to neutral, with the oven switch on,
>> is 17 ohms. That makes sense
>> to me. However the impedance reading from neutral to ground makes no
>> sense to me. I've tried two different dvm's and they both give
>> bizarre results. When starting at the 2M ohm range, the meter starts
>> at about 700k and counts
>> down to about 300k and holds there. When I move the switch over to
>> the 20M ohm range, the meter starts at about 2.3M ohm and counts up.
>> The other meter
>> which is a portable meter counts backward too and then the minus sign
>> appears on the meter as if current is coming into the meter. From
>> what I can
>> see, there aren't any capacitors or semiconductors interfering. The
>> oven thermostat has a thermocouple wired to it which for some reason
>> is not shown
>> in the schematic. I opened the thermostat and found an interesting
>> mechanical coupling that moves a slider bar that depresses either
>> the oven element switch, the broil element switch, or both. Then
>> there is the thermocouple wire which is wrapped(?) internally around
>> the rotating control
>> that selects the oven temperature. I don't usually open oven
>> thermostats so
>> I'm not sure what exactly is going on inside because once you open
>> the thermostat,
>> there is a spring inside the device which displaces everything. In
>> any case, at room
>> temperature, there is a connection from L1 to the bake and broil
>> terminals so I know
>> it's sending power through to those elements.
>>
>> Not trusting anything about these electrical readings, I first
>> plugged the oven into my Sencore PR57 isolation transformer. The
>> transformer can only supply about 300 watts but I was more
>> interested in measuring leakage current. No surprise when the low
>> side leakage to the metal frame measured full deflection even with
>> the power off to the oven. Not exactly the best situation. The high
>> side leakage was zero. I turned up the voltage slowly and the
>> current seemed to rise proportionately to the 17 ohm load until I
>> stopped at about 300 watts. I should mention that the heating
>> element did not seem to get warm. Also, the heating element
>> impedance matched the load across the power plug so that seemed like
>> a good sign. Then I plugged it directly into the wall outlet via the
>> Kill-A-Watt
>> meter. I
>> turned on the oven switch and an instant trip of the circuit breaker
>> at the
>> sub panel occurred. So where is all this extra current coming from
>> to cook the ground plug on my Kill-A-Watt and trip the breaker? I
>> must be missing something very obvious.
>>
>> Thanks for your reply.
>> --
>> David Farber
>> Los Osos, CA

Wild_Bill wrote:
> I'm not really sure which heating element is still connected. Most of
> the elements' wattages are listed on the wiring diagram, but the two
> on the left side (bake, broil) of the diagram aren't (that I could
> see). It could be, that the wattage of the element being used exceeds the
> total wattage of the circuit breaker.
> I would check to see if there are any other loads applied to the same
> AC supply circuit.
>
> Those temperature control symbols may represent the type that have
> internal heated bi-metal type switches in them (dunno what they're
> called in the trade, but commonly used in cooking appliances with
> heating elements). In some Corning laboratory type hot plates that I have,
> these types of
> switches make a fairly distinct sound.. a sort-of "tink" when the
> when the switch's internal heated bi-metal strip opens the switch.
> I believe a cam closes the switch contacts, then the heated bi-metal
> strip opens the switch (a calculated/designed time delay, I guess).
>
> The small bi-metal heater wire (inside the switch(s) will naturally
> have a DC resistance. I wouldn't think that internal heater wire
> resistance would change from just a DMM test lead voltage, but maybe
> they do. If I could get to those lab hot plates, I'd do some checking
> instead of just speculating.

Hi WB,

There's an upper and a lower element in the stove section. The top one is
called the broil and bottom one is the bake. When you turn the stove knob
from off to on, both broil and bake elements get energized. I disconnected
the broil element because I will not be doing any broiling. So what's left
is the bake element at the bottom. That presents about a 17 ohm load which
translates into approximately 850 watts. If the supply voltage were 240V,
that would increase the power to 3,400 watts. I'm not even sure 850 watts
can raise the temperature to 200°F (assuming I can get it working) in a
reasonable amount of time. Regarding the circuit breaker, there was really
nothing else on that circuit at the time it tripped. Even so, why would the
ground terminal be the one to take the hit? There shouldn't be any current
flowing through there, right? The way the stove is wired now is that the
neutral wire of the stove is connected to where L2 was before so the circuit
path is from L1, through the oven switch, through the heating element,
through L2 which is now wired to neutral.

Thanks for your reply.
--
David Farber
Los Osos, CA

== 2 of 3 ==
Date: Thurs, Oct 21 2010 6:40 pm
From: "Brenda Ann"

"David Farber" <farberbear.unspam@aol.com> wrote in message
news:i9qklm$oda$1@news.eternal-september.org...
Regarding the circuit breaker, there was really
> nothing else on that circuit at the time it tripped. Even so, why would
> the ground terminal be the one to take the hit? There shouldn't be any
> current flowing through there, right? The way the stove is wired now is
> that the neutral wire of the stove is connected to where L2 was before so
> the circuit path is from L1, through the oven switch, through the heating
> element, through L2 which is now wired to neutral.
>
> Thanks for your reply.

David,

Is the breaker a GFCI type? That would explain the tripping, as the way you
have the stove wired, there is a large potential between neutral and ground
(in terms of a GFCI).

== 3 of 3 ==
Date: Thurs, Oct 21 2010 7:28 pm
From: "David Farber"

Brenda Ann wrote:
> "David Farber" <farberbear.unspam@aol.com> wrote in message
> news:i9qklm$oda$1@news.eternal-september.org...
> Regarding the circuit breaker, there was really
>> nothing else on that circuit at the time it tripped. Even so, why
>> would the ground terminal be the one to take the hit? There
>> shouldn't be any current flowing through there, right? The way the
>> stove is wired now is that the neutral wire of the stove is
>> connected to where L2 was before so the circuit path is from L1,
>> through the oven switch, through the heating element, through L2
>> which is now wired to neutral. Thanks for your reply.
>
> David,
>
> Is the breaker a GFCI type? That would explain the tripping, as the
> way you have the stove wired, there is a large potential between
> neutral and ground (in terms of a GFCI).

Not a GFCI. The circuit breaker is 20 amps and located in the sub panel.

How do you account for the large potential between neutral and ground? Since
there is no oven light or clock, the neutral wire in the schematic doesn't
really connect to anything except the chassis ground. Though I do agree with
you that in order for that circuit to trip and burn out the ground pin,
there is some major current flowing. I'd just like to be able to follow it
from beginning to end.

Thanks for your reply.
--
David Farber
Los Osos, CA

==============================================================================
TOPIC: Sometimes, a sledge - hammer is the right tool ... :-)
http://groups.google.com/group/sci.electronics.repair/t/2bc7695b4fb03244?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Oct 21 2010 5:30 pm
From: "Arfa Daily"

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:i9pn2m$52j$1@news.eternal-september.org...
> I'm not sure "sledgehammer" is quite the right term.
>
> It would be more correct to say that you handed the device sufficient rope
> to hang itself.
>
>

It was the right term for me. I was trying to conjour the image of a piece
of delicate electronic equipment, dealt with (successfully) by the use of a
bludgeoning and completely inappropriate 'tool' ...

Probably one of those east - west humour things again.

Arfa

== 2 of 2 ==
Date: Thurs, Oct 21 2010 5:56 pm
From: "William Sommerwerck"

>> I'm not sure "sledgehammer" is quite the right term.
>> It would be more correct to say that you handed the
>> device sufficient rope to hang itself.

> It was the right term for me. I was trying to conjour the
> image of a piece of delicate electronic equipment, dealt
> with (successfully) by the use of a bludgeoning and
> completely inappropriate 'tool' ...

We're having some fun, so don't anybody get too serious...

I don't see what was inappropriate about the tool, nor do I consider what
you did "bludgeoning". If anything, it was quite the opposite -- not unlike
handing a man with a leg injury a cane so he could stand up. Once he's
standing, you can more-easily locate the injury.

==============================================================================
TOPIC: Popularity of the small and medium-size Adidas Porsche Design
http://groups.google.com/group/sci.electronics.repair/t/aff5e6c77b3dfa0e?hl=en
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== 1 of 1 ==
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==============================================================================
TOPIC: Good LED TV repair men in San Diego County area?
http://groups.google.com/group/sci.electronics.repair/t/4ed1121fdbf133bb?hl=en
==============================================================================

== 1 of 1 ==
Date: Thurs, Oct 21 2010 7:04 pm
From: "Michael Kennedy"

"Keith" <keithdlee2000@gmail.com> wrote in message
news:i9npfh$hqe$1@news.eternal-september.org...
> All:
> Does anyone know of a safe, reliable, and honest LED TV repairman in the
> San Diego County area? If so,
> please email or post me here.
>
> Keith

First of all, how has it failed? If it has failed due to impact damage and
the screen is broken, it isnt econoical to fix it. As others have stated it
should be covered under the manufacturers warranty still.

Mike

==============================================================================
TOPIC: Testing SMPS
http://groups.google.com/group/sci.electronics.repair/t/1cc72f0926af56cc?hl=en
==============================================================================

== 1 of 2 ==
Date: Thurs, Oct 21 2010 7:31 pm
From: "Michael Kennedy"

I am finally getting back to working on this Plasma TV that occasionally
shuts down.

I would like to isolate the power supply to be certain that it is where the
problem lies. I have tried powering it up using 2 100V light bulbs as a load
on the 60v and 80v rails to no avail. It doesnt attempt to power up unless
it is attached to the Y-sus board.

Im guessing it gets some kind of ok signal from the VSS line?? Or is the
150W light bulb not enough of a load?

== 2 of 2 ==
Date: Thurs, Oct 21 2010 9:11 pm
From: "circuit"

Usually with a ticking problem, I will pull the cathodes of each diode one
at a time that are located on the secondary side of the SMPS xfmr, and power
up. When the ticking stops, then you have found the DC line causing the
problem.

"Michael Kennedy" <mike@com> wrote in message
news:qLudnW4o9Jhha13RnZ2dnVY3goydnZ2d@giganews.com...
>I am finally getting back to working on this Plasma TV that occasionally
>shuts down.
>
> I would like to isolate the power supply to be certain that it is where
> the problem lies. I have tried powering it up using 2 100V light bulbs as
> a load on the 60v and 80v rails to no avail. It doesnt attempt to power up
> unless it is attached to the Y-sus board.
>
> Im guessing it gets some kind of ok signal from the VSS line?? Or is the
> 150W light bulb not enough of a load?

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