GE Microwave JVM1540DM3WW Everything but Heat

[Phil Allison]

"Arfa Daily"

Doing that, I discovered my microwave, labeled 900w, actually delivered
250w.


Then it was either faulty, or your maths is suspect. The quoted power on a
microwave oven is its output power, which is different from its line input
power, which will be quoted separately on the item's rating plate.

** Correct.

A couple of things will tend to under rate the actual heat power delivered
by a microwave oven tested with a vessel of water.

1. An unsuitable vessel can absorb much of the energy.

2. Heat is lost to the surrounding air during the test.

3. The thermometer will usually under read the actual temperature rise.

So, use at least half a litre of water in a thin walled plastic container
and heat the water to no more than 60 degrees C.

Be damn quick with the thermometer and even then allow 10% for losses.



..... Phil

 

[amdx]

On 4/5/2013 3:16 PM, William Sommerwerck wrote:

I'd love to see what a large wedge would do to a modern
microwave oven, other than go right though the entire thing,
like a cup of to-go soup when the lids comes loose and it
instantly dissolves the paper bag you were holding seconds
earlier.

I have a near-end-of-American-manufacture LItton that's built like a
tank. Haven't used it in a few years, but it'll still be working when
I'm dead. Only problem is that the cavity's on the small side.

I have a working Frigidaire microwave that was manufactured in 1983.
The specs say 1.38 KW 120V 60HZ, a little odd, now it would be amps not
KW. Don't know about the output power, nothing on the unit, and the
owners manual says nothing about the power. The model number is MC800M,
I would think 800W is to low for the output power. But, I'm curious what
is the efficiency of a magnetron?
Mikek

PS. The owners manual says " If you move or sell the microwave to
another person please report the change so we can update our records.
Hope I'm not in trouble, I've moved 5 times without reporting.

 

[amdx]

On 4/5/2013 7:29 PM, William Sommerwerck wrote:

It's digital but you have to enter cooking times in this format
[time button] [enter the time] [time button] then [start]
It may be built around a soviet RPL calculator chipset.

It sounds as if whoever wrote the code didn't want to have to keep a
running calculation of the number of seconds -- just do it once with the
second [time button] press. Of course, it could have been done at
[start] just as well.

The GE Jet in my range hood has a simple and easily understood entry
system.

I'm amazed how many microwave ovens have confusing and complex
systems.

No kidding, just give me a knob that I can spin to the minutes I want.
Mikek

 

[amdx]

On 4/7/2013 5:31 AM, Leif Neland wrote:

Ian Field skrev den 05/04/2013:


With the cost of parts & labour these days compared to what new ones
cost, it may not be worth throwing good money after bad! I have the
advantage of living in a block of flats, where a microwave gets left
in the bin room every so often - if I don't need a replacement I
simply strip it for spares. That way I have a selection of magnetrons
with the various flange configurations.


Another thing to consider is the resulting effect of the microwave.

Using these formulas:

1 Ws = 1J

4.184 J for the temperature of one gram of water to increase 1 degree
Celsius (°C).

Then take the time for 100g=1dl tap-water to boil from tap-temperature,
perhaps 10C, it is easy to calculate the resulting effect.

(And here you see the advantage of using metric, instead of units based
on the length of king X's thumb and the volume of his bladder or
whatever )

Doing that, I discovered my microwave, labeled 900w, actually delivered
250w.

I don't know if it still takes 900w from the mains, but I discarded it
and replaced it.

technically, you might have called it "working"

Leif


Is it necessarily true that all the microwaves leaving the magnetron

are being focused in your bowl of water?
Mikek

 

[William Sommerwerck]

Is it necessarily true that all the microwaves leaving the
magnetron are being focused in your bowl of water?

Those that miss the bowl bounce around until they're absorbed.

 

[Ian Field]

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:asd5ueF3s83U1@mid.individual.net...

"Arfa Daily"

Doing that, I discovered my microwave, labeled 900w, actually delivered
250w.


Then it was either faulty, or your maths is suspect. The quoted power on
a microwave oven is its output power, which is different from its line
input power, which will be quoted separately on the item's rating plate.


** Correct.

A couple of things will tend to under rate the actual heat power delivered
by a microwave oven tested with a vessel of water.

1. An unsuitable vessel can absorb much of the energy.

When I heat a cup of water - even in a glass cup, I have to put the cup in
the corner just inside the door, with the handle tucked right into the
corner - or the handle gets hot.

I picked up one or two blisters before I learned that lesson!

When I repaired microwaves for a living, I invariably got a few otherwise
working but not fit for sale - I enthusiastically tested a few of these to
destruction with things that shouldn't be put in the microwave.

Glass conducts electricity quite well when its hot enough to glow red.

 

[Ian Field]

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:kjrs6o$dpo$1@dont-email.me...

Is it necessarily true that all the microwaves leaving the magnetron are
being focused in your bowl of water?

Those that miss the bowl bounce around until they're absorbed.

Some ovens have a "pin-pivot" set of vanes hidden behind a low dielectric
ceramic panel, the microwaves bouncing off the vanes pushes them round; thus
causing a constantly varied angle of incidence for the waves to bounce
around the compartment.

 

[William Sommerwerck]

I've not seen this in years, or goofy stuff like temperate
probes either.

I prefer the intemperate ones... Much more fun.

Who really cooks a turkey in the microwave?

No one in their right mind.

Microwave ovens don't actually cook anything. They just heat it.

 

[Phil Allison]

"amdx"

I have a working Frigidaire microwave that was manufactured in 1983.
The specs say 1.38 KW 120V 60HZ, a little odd, now it would be amps not
KW. Don't know about the output power, nothing on the unit, and the owners
manual says nothing about the power. The model number is MC800M,
I would think 800W is to low for the output power. But, I'm curious what
is the efficiency of a magnetron?

** My Samsung MB245 is rated at 1000W and has a nameplate consumption of
1650W.

The AC current draw is 7 amps at 240V.


..... Phil

 

[Cydrome Leader]

Ian Field <gangprobing.alien@ntlworld.com> wrote:

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:kjrs6o$dpo$1@dont-email.me...
Is it necessarily true that all the microwaves leaving the magnetron are
being focused in your bowl of water?

Those that miss the bowl bounce around until they're absorbed.


Some ovens have a "pin-pivot" set of vanes hidden behind a low dielectric
ceramic panel, the microwaves bouncing off the vanes pushes them round; thus
causing a constantly varied angle of incidence for the waves to bounce
around the compartment.

I've not seen this in years, or goofy stuff like temperate probes either.

Who really cooks a turkey in the microwave?

 

[Cydrome Leader]

amdx <amdx@knologynotthis.net> wrote:

On 4/5/2013 3:16 PM, William Sommerwerck wrote:
I'd love to see what a large wedge would do to a modern
microwave oven, other than go right though the entire thing,
like a cup of to-go soup when the lids comes loose and it
instantly dissolves the paper bag you were holding seconds
earlier.

I have a near-end-of-American-manufacture LItton that's built like a
tank. Haven't used it in a few years, but it'll still be working when
I'm dead. Only problem is that the cavity's on the small side.

I have a working Frigidaire microwave that was manufactured in 1983.
The specs say 1.38 KW 120V 60HZ, a little odd, now it would be amps not
KW. Don't know about the output power, nothing on the unit, and the
owners manual says nothing about the power. The model number is MC800M,
I would think 800W is to low for the output power. But, I'm curious what
is the efficiency of a magnetron?
Mikek

Mine has a spec sheet indicating input power of 1.25kW and 14.5A and
output power of 70 to 700W in 10 steps, or 56% efficient as a whole. I'd
hope new ones are slightly better than this. This thing also has a listed
weight of 80 pounds which is without question, accurate. The manufacture
date is June, 1981. It's possible the 700W is optimistic, but at least
more honest than the numbers you see on vacuum cleaners, like 6
horsepower.

PS. The owners manual says " If you move or sell the microwave to
another person please report the change so we can update our records.
Hope I'm not in trouble, I've moved 5 times without reporting.

Mine mentions not to put the temperature probe into frozen food as
breakage can occur, and that you should not dry clothing or wet newspapers
with it.

When did they start to plastic bag newspapers?

 

[Trevor Wilson]

On 4/4/2013 2:06 PM, kflook67@gmail.com wrote:

Everything operates correctly, except no heat. I can hear a transformer hum, come and go while it acts like it is working, like it is trying to run, but nothing heats. I understand electrical systems and have read considerable about troubleshooting and repair. I just wanted to ask before undertaking this task. Based on the circumstances with the on and off hum, what do you think?

Thank you ...Ken

**Commonly, the fault is that the magnetron has failed. HOWEVER, as PA
mentioned, inexperienced people should NEVER attempt to repair a
microwave oven. Even after switching off, sufficient energy may be
stored in the main filter cap to kill a human. When powered up, the
danger is further magnified. 2,000 Volts at 0.5 Amp will easily kill.

--
Trevor Wilson www.rageaudio.com.au

 

[Ian Field]

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:asgo5oFsorjU1@mid.individual.net...

On 4/4/2013 2:06 PM, kflook67@gmail.com wrote:
Everything operates correctly, except no heat. I can hear a transformer
hum, come and go while it acts like it is working, like it is trying to
run, but nothing heats. I understand electrical systems and have read
considerable about troubleshooting and repair. I just wanted to ask
before undertaking this task. Based on the circumstances with the on and
off hum, what do you think?

Thank you ...Ken


**Commonly, the fault is that the magnetron has failed. HOWEVER, as PA
mentioned, inexperienced people should NEVER attempt to repair a microwave
oven. Even after switching off, sufficient energy may be stored in the
main filter cap to kill a human.

Utter rubbish! - the mains filter cap is insignificant, its the hefty cap in
the doubler circuit that could be dangerous.


The transformer secondary delivers 2kV at enough current to guarantee
lethality, it can strike an arc to your hand through a cracked screwdriver
handle and kill you!

The capacitor in the doubler is typically 0.9uF - 1uF and can remain charged
upto some proportion of 2kV.

 

[Trevor Wilson]

On 4/9/2013 7:11 AM, Ian Field wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:asgo5oFsorjU1@mid.individual.net...
On 4/4/2013 2:06 PM, kflook67@gmail.com wrote:
Everything operates correctly, except no heat. I can hear a
transformer hum, come and go while it acts like it is working, like
it is trying to run, but nothing heats. I understand electrical
systems and have read considerable about troubleshooting and repair.
I just wanted to ask before undertaking this task. Based on the
circumstances with the on and off hum, what do you think?

Thank you ...Ken


**Commonly, the fault is that the magnetron has failed. HOWEVER, as PA
mentioned, inexperienced people should NEVER attempt to repair a
microwave oven. Even after switching off, sufficient energy may be
stored in the main filter cap to kill a human.

Utter rubbish! - the mains filter cap is insignificant, its the hefty
cap in the doubler circuit that could be dangerous.

**I said:

"...the MAIN filter cap..." Not MAINS filter cap (whatever that is). I
did not assume a SMPS, rather a linear supply. The cap in question can
store several kV.

The transformer secondary delivers 2kV at enough current to guarantee
lethality, it can strike an arc to your hand through a cracked
screwdriver handle and kill you!

**Of course.

The capacitor in the doubler is typically 0.9uF - 1uF and can remain
charged upto some proportion of 2kV.

**That is exactly what I stated.


--
Trevor Wilson www.rageaudio.com.au

 

[William Sommerwerck]

"Cydrome Leader" wrote in message news:kjvhv6$9ch$1@reader1.panix.com...
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

Microwave ovens don't actually cook anything. They just heat it.

They are unsurpassed for stuff like frozen burritos or fresh broccoli.

And they're perfect for bacon. The microwave oven is the bachelor's friend.

 

[Cydrome Leader]

William Sommerwerck <grizzledgeezer@comcast.net> wrote:

I've not seen this in years, or goofy stuff like temperate
probes either.

I prefer the intemperate ones... Much more fun.


Who really cooks a turkey in the microwave?

No one in their right mind.

Microwave ovens don't actually cook anything. They just heat it.

they are unsurpassed for stuff like frozen burritos or fresh broccoli.

And also accumulating that microwave oven smell, no matter what's heated
up in them.

 

[Cydrome Leader]

Ian Field <gangprobing.alien@ntlworld.com> wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:asgo5oFsorjU1@mid.individual.net...
On 4/4/2013 2:06 PM, kflook67@gmail.com wrote:
Everything operates correctly, except no heat. I can hear a transformer
hum, come and go while it acts like it is working, like it is trying to
run, but nothing heats. I understand electrical systems and have read
considerable about troubleshooting and repair. I just wanted to ask
before undertaking this task. Based on the circumstances with the on and
off hum, what do you think?

Thank you ...Ken


**Commonly, the fault is that the magnetron has failed. HOWEVER, as PA
mentioned, inexperienced people should NEVER attempt to repair a microwave
oven. Even after switching off, sufficient energy may be stored in the
main filter cap to kill a human.

Utter rubbish! - the mains filter cap is insignificant, its the hefty cap in
the doubler circuit that could be dangerous.


The transformer secondary delivers 2kV at enough current to guarantee
lethality, it can strike an arc to your hand through a cracked screwdriver
handle and kill you!

The capacitor in the doubler is typically 0.9uF - 1uF and can remain charged
upto some proportion of 2kV.

plus you need a good pair of leather gloves just to open them these days.
The sheet metal (foil?) they use, especially the stainless is unbelievably
sharp on the inner edges.

 

[Cydrome Leader]

William Sommerwerck <grizzledgeezer@comcast.net> wrote:

"Cydrome Leader" wrote in message news:kjvhv6$9ch$1@reader1.panix.com...
William Sommerwerck <grizzledgeezer@comcast.net> wrote:

Microwave ovens don't actually cook anything. They just heat it.

They are unsurpassed for stuff like frozen burritos or fresh broccoli.

And they're perfect for bacon. The microwave oven is the bachelor's friend.

I always found microwave bacon creepy.

di you have one of those weird "browning dishes" with the metal oxide
coating?

 

[William Sommerwerck]

And they're perfect for bacon. The microwave oven
is the bachelor's friend.

I always found microwave bacon creepy.

You mean it moves?

You're probably not cooking it enough. You can "blast" it in a microwave
without burning, if you so desire.

Did you have one of those weird "browning dishes"
with the metal oxide coating?

No, I never did. Are they still made?

 

[Ian Field]

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:kjvi8j$9ch$2@reader1.panix.com...

Ian Field <gangprobing.alien@ntlworld.com> wrote:


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:asgo5oFsorjU1@mid.individual.net...
On 4/4/2013 2:06 PM, kflook67@gmail.com wrote:
Everything operates correctly, except no heat. I can hear a transformer
hum, come and go while it acts like it is working, like it is trying to
run, but nothing heats. I understand electrical systems and have read
considerable about troubleshooting and repair. I just wanted to ask
before undertaking this task. Based on the circumstances with the on
and
off hum, what do you think?

Thank you ...Ken


**Commonly, the fault is that the magnetron has failed. HOWEVER, as PA
mentioned, inexperienced people should NEVER attempt to repair a
microwave
oven. Even after switching off, sufficient energy may be stored in the
main filter cap to kill a human.

Utter rubbish! - the mains filter cap is insignificant, its the hefty cap
in
the doubler circuit that could be dangerous.


The transformer secondary delivers 2kV at enough current to guarantee
lethality, it can strike an arc to your hand through a cracked
screwdriver
handle and kill you!

The capacitor in the doubler is typically 0.9uF - 1uF and can remain
charged
upto some proportion of 2kV.

plus you need a good pair of leather gloves just to open them these days.
The sheet metal (foil?) they use, especially the stainless is unbelievably
sharp on the inner edges.

VCRs were just as bad before they started making *EVERYTHING* out of
plastic.