microwave

[Ian Field]

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgskoeFh849U1@mid.individual.net...

On 28/01/2016 6:11 AM, Ian Field wrote:


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgqimnF1cklU1@mid.individual.net...
On 27/01/2016 11:45 AM, Robert wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgq4pcFsiiiU1@mid.individual.net...
On 26/01/2016 3:51 PM, Robert wrote:
I turned an empty microwave on for about 30 seconds. What is the
potential damage I have caused?

**Magnetrons take around 2 seconds to reach maximum output. So, you
have operated the magnetron for 28 seconds with no load. As others
have stated, you have probably not caused fatal damage to the
magnetron (around 1 minute or more will almost certainly cause that)

how do you know that 1 minute is the crucial time?

**My words (note the new emphasis):

"around 1 minute *OR MORE* will almost certainly cause that"

Just for kicks - I jammed the fan on a unit with a low emission mag and
run it empty for the maximum timer duration.

I was sort of expecting something entertaining to happen - instead; the
magnetron recovered to a useable condition.

**SWMBO decided to heat up some sesame seeds. 3 mins on high and magnetron
output was dramatically reduced. I figure that what was a 900 Watt MO was
suddenly a 300 Watt MO. A magnetron swap brought it back to new
performance. Instructions were then issued to ensure adequate quantities
of food and/or water is used in future.

My favourite is an old TV valve - the glass is lossy enough to get red hot
and melt, the vacuum sucks it onto the internal structure like cling film.

 

[Trevor Wilson]

On 28/01/2016 8:53 AM, Ian Field wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgskoeFh849U1@mid.individual.net...
On 28/01/2016 6:11 AM, Ian Field wrote:


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgqimnF1cklU1@mid.individual.net...
On 27/01/2016 11:45 AM, Robert wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgq4pcFsiiiU1@mid.individual.net...
On 26/01/2016 3:51 PM, Robert wrote:
I turned an empty microwave on for about 30 seconds. What is the
potential damage I have caused?

**Magnetrons take around 2 seconds to reach maximum output. So, you
have operated the magnetron for 28 seconds with no load. As others
have stated, you have probably not caused fatal damage to the
magnetron (around 1 minute or more will almost certainly cause that)

how do you know that 1 minute is the crucial time?

**My words (note the new emphasis):

"around 1 minute *OR MORE* will almost certainly cause that"

Just for kicks - I jammed the fan on a unit with a low emission mag and
run it empty for the maximum timer duration.

I was sort of expecting something entertaining to happen - instead; the
magnetron recovered to a useable condition.

**SWMBO decided to heat up some sesame seeds. 3 mins on high and
magnetron output was dramatically reduced. I figure that what was a
900 Watt MO was suddenly a 300 Watt MO. A magnetron swap brought it
back to new performance. Instructions were then issued to ensure
adequate quantities of food and/or water is used in future.

My favourite is an old TV valve - the glass is lossy enough to get red
hot and melt, the vacuum sucks it onto the internal structure like cling
film.

**Sweet. I actually had a guitar amp on the bench one day, where the
plate on one output valve had become so hot that the envelope was sucked
in, to the point where it developed tiny hole in the glass and the
vacuum escaped.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[~misfit~]

Once upon a time on usenet Ian Field wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgsp74Fic3lU1@mid.individual.net...
On 27/01/2016 5:25 PM, Robert wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:66bfb608-92ae-411f-8577-ab9dcd398235@googlegroups.com...
Robert wrote:
"Phil Allison"

** Potentially, it can cause arcing in the wave guide leading to
the > oven enclosure. Then a fuse blows.

However, most microwave ovens are immune from the effect, but
makers > still advise never to do it.

I happen to own one that isn't immune, a Samsung MB245.

I cannot use it to thaw a frozen bottle of lemonade, or it arcs
up.

Mine is a new Samsung ME73M.

What do you mean by 'arc up' ?


** A few seconds after the oven is switched on, a visible and
audible arc starts up at the top of the wave guide - just behind
the mica window. It quickly burns the paint in that area and the
oven must be switched off immediately.


I did hear a loud sound as soon as I switched the oven on while
empty, which is the first time I switched it on. I wouldn't be
surprised if the oven is damaged from what I did.

It seems crazy that just having the oven for a few seconds could
damage it.

**Well, you're feeding something like 1.5kW into the MO, most of
which ends up being used by the magnetron. The energy has to be
dissipated somewhere. Where do you think all that energy should go?

Drawing that much power from the mains usually only gets you about
700 - 800W of cooking power. Half of it produces heat anyway.

Apparently the potential for damage is in standing waves and
reflections within the cooking compartment. There's usually some form
of pin-bearing light alloy vanes to scatter the beam and constantly
vary the "mode" - so its pretty random anyway whether the waves will
be reflected directly back into the waveguide.

With a big fat turkey in there, all the waves get absorbed - in theory
anyway.

Interesting thread. My thanks to the contributers, I learned a lot about
microwave ovens.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)

 

[Ian Field]

"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:n8bron$52f$1@dont-email.me...

Once upon a time on usenet Ian Field wrote:
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgsp74Fic3lU1@mid.individual.net...
On 27/01/2016 5:25 PM, Robert wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:66bfb608-92ae-411f-8577-ab9dcd398235@googlegroups.com...
Robert wrote:
"Phil Allison"

** Potentially, it can cause arcing in the wave guide leading to
the > oven enclosure. Then a fuse blows.

However, most microwave ovens are immune from the effect, but
makers > still advise never to do it.

I happen to own one that isn't immune, a Samsung MB245.

I cannot use it to thaw a frozen bottle of lemonade, or it arcs
up.

Mine is a new Samsung ME73M.

What do you mean by 'arc up' ?


** A few seconds after the oven is switched on, a visible and
audible arc starts up at the top of the wave guide - just behind
the mica window. It quickly burns the paint in that area and the
oven must be switched off immediately.


I did hear a loud sound as soon as I switched the oven on while
empty, which is the first time I switched it on. I wouldn't be
surprised if the oven is damaged from what I did.

It seems crazy that just having the oven for a few seconds could
damage it.

**Well, you're feeding something like 1.5kW into the MO, most of
which ends up being used by the magnetron. The energy has to be
dissipated somewhere. Where do you think all that energy should go?

Drawing that much power from the mains usually only gets you about
700 - 800W of cooking power. Half of it produces heat anyway.

Apparently the potential for damage is in standing waves and
reflections within the cooking compartment. There's usually some form
of pin-bearing light alloy vanes to scatter the beam and constantly
vary the "mode" - so its pretty random anyway whether the waves will
be reflected directly back into the waveguide.

With a big fat turkey in there, all the waves get absorbed - in theory
anyway.

Interesting thread. My thanks to the contributers, I learned a lot about
microwave ovens.

There's a TV programme called; Brainiac - Science Abuse.

The decided to microwave a bottle of Champaign.

They used a portable generator so they could run the microwave in the middle
of a field, and telephoto lens so the camera crew was out of range of the
shrapnel.

The microwave came apart like a soggy cardboard box - both the inner
compartment and outer casing.

 

[Trevor Wilson]

On 29/01/2016 6:19 AM, Ian Field wrote:

"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:n8bron$52f$1@dont-email.me...
Once upon a time on usenet Ian Field wrote:
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgsp74Fic3lU1@mid.individual.net...
On 27/01/2016 5:25 PM, Robert wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:66bfb608-92ae-411f-8577-ab9dcd398235@googlegroups.com...
Robert wrote:
"Phil Allison"

** Potentially, it can cause arcing in the wave guide leading to
the > oven enclosure. Then a fuse blows.

However, most microwave ovens are immune from the effect, but
makers > still advise never to do it.

I happen to own one that isn't immune, a Samsung MB245.

I cannot use it to thaw a frozen bottle of lemonade, or it arcs
up.

Mine is a new Samsung ME73M.

What do you mean by 'arc up' ?


** A few seconds after the oven is switched on, a visible and
audible arc starts up at the top of the wave guide - just behind
the mica window. It quickly burns the paint in that area and the
oven must be switched off immediately.


I did hear a loud sound as soon as I switched the oven on while
empty, which is the first time I switched it on. I wouldn't be
surprised if the oven is damaged from what I did.

It seems crazy that just having the oven for a few seconds could
damage it.

**Well, you're feeding something like 1.5kW into the MO, most of
which ends up being used by the magnetron. The energy has to be
dissipated somewhere. Where do you think all that energy should go?

Drawing that much power from the mains usually only gets you about
700 - 800W of cooking power. Half of it produces heat anyway.

Apparently the potential for damage is in standing waves and
reflections within the cooking compartment. There's usually some form
of pin-bearing light alloy vanes to scatter the beam and constantly
vary the "mode" - so its pretty random anyway whether the waves will
be reflected directly back into the waveguide.

With a big fat turkey in there, all the waves get absorbed - in theory
anyway.

Interesting thread. My thanks to the contributers, I learned a lot
about microwave ovens.

There's a TV programme called; Brainiac - Science Abuse.

The decided to microwave a bottle of Champaign.

They used a portable generator so they could run the microwave in the
middle of a field, and telephoto lens so the camera crew was out of
range of the shrapnel.

The microwave came apart like a soggy cardboard box - both the inner
compartment and outer casing.

**I really loved Brainiac. Best episode was the one where they were
experimenting with highly reactive metals, water and a bathtub. Lots of
explosions.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Ian Field]

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgv98aF6rthU1@mid.individual.net...

On 29/01/2016 6:19 AM, Ian Field wrote:


"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:n8bron$52f$1@dont-email.me...
Once upon a time on usenet Ian Field wrote:
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgsp74Fic3lU1@mid.individual.net...
On 27/01/2016 5:25 PM, Robert wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:66bfb608-92ae-411f-8577-ab9dcd398235@googlegroups.com...
Robert wrote:
"Phil Allison"

** Potentially, it can cause arcing in the wave guide leading to
the > oven enclosure. Then a fuse blows.

However, most microwave ovens are immune from the effect, but
makers > still advise never to do it.

I happen to own one that isn't immune, a Samsung MB245.

I cannot use it to thaw a frozen bottle of lemonade, or it arcs
up.

Mine is a new Samsung ME73M.

What do you mean by 'arc up' ?


** A few seconds after the oven is switched on, a visible and
audible arc starts up at the top of the wave guide - just behind
the mica window. It quickly burns the paint in that area and the
oven must be switched off immediately.


I did hear a loud sound as soon as I switched the oven on while
empty, which is the first time I switched it on. I wouldn't be
surprised if the oven is damaged from what I did.

It seems crazy that just having the oven for a few seconds could
damage it.

**Well, you're feeding something like 1.5kW into the MO, most of
which ends up being used by the magnetron. The energy has to be
dissipated somewhere. Where do you think all that energy should go?

Drawing that much power from the mains usually only gets you about
700 - 800W of cooking power. Half of it produces heat anyway.

Apparently the potential for damage is in standing waves and
reflections within the cooking compartment. There's usually some form
of pin-bearing light alloy vanes to scatter the beam and constantly
vary the "mode" - so its pretty random anyway whether the waves will
be reflected directly back into the waveguide.

With a big fat turkey in there, all the waves get absorbed - in theory
anyway.

Interesting thread. My thanks to the contributers, I learned a lot
about microwave ovens.

There's a TV programme called; Brainiac - Science Abuse.

The decided to microwave a bottle of Champaign.

They used a portable generator so they could run the microwave in the
middle of a field, and telephoto lens so the camera crew was out of
range of the shrapnel.

The microwave came apart like a soggy cardboard box - both the inner
compartment and outer casing.

**I really loved Brainiac. Best episode was the one where they were
experimenting with highly reactive metals, water and a bathtub. Lots of
explosions.

A lot of motorists will have liked the run of exploding caravans.

The one on fuel for flatulence was a bit of a let down.

 

[Ian Field]

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgssrbFj96uU1@mid.individual.net...

On 28/01/2016 8:53 AM, Ian Field wrote:


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgskoeFh849U1@mid.individual.net...
On 28/01/2016 6:11 AM, Ian Field wrote:


"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgqimnF1cklU1@mid.individual.net...
On 27/01/2016 11:45 AM, Robert wrote:

"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in message
news:dgq4pcFsiiiU1@mid.individual.net...
On 26/01/2016 3:51 PM, Robert wrote:
I turned an empty microwave on for about 30 seconds. What is the
potential damage I have caused?

**Magnetrons take around 2 seconds to reach maximum output. So, you
have operated the magnetron for 28 seconds with no load. As others
have stated, you have probably not caused fatal damage to the
magnetron (around 1 minute or more will almost certainly cause that)

how do you know that 1 minute is the crucial time?

**My words (note the new emphasis):

"around 1 minute *OR MORE* will almost certainly cause that"

Just for kicks - I jammed the fan on a unit with a low emission mag and
run it empty for the maximum timer duration.

I was sort of expecting something entertaining to happen - instead; the
magnetron recovered to a useable condition.

**SWMBO decided to heat up some sesame seeds. 3 mins on high and
magnetron output was dramatically reduced. I figure that what was a
900 Watt MO was suddenly a 300 Watt MO. A magnetron swap brought it
back to new performance. Instructions were then issued to ensure
adequate quantities of food and/or water is used in future.

My favourite is an old TV valve - the glass is lossy enough to get red
hot and melt, the vacuum sucks it onto the internal structure like cling
film.

**Sweet. I actually had a guitar amp on the bench one day, where the plate
on one output valve had become so hot that the envelope was sucked in, to
the point where it developed tiny hole in the glass and the vacuum
escaped.

That wasn't exactly unusual on the old valve CTVs, mostly horizontal output
valves, but I've seen one or two vertical pentodes go the same way.

It sometimes happened to the efficiency diode on the old B&W TVs - they were
seriously thrashed at the best of times, even the ones that didn't fail
catastrophically were heavily shadowed inside the envelope after a few years
use.

 

[Phil Allison]

Ian Field wrote:

There's a TV programme called; Brainiac - Science Abuse.

The decided to microwave a bottle of Champaign.

They used a portable generator so they could run the microwave in the middle
of a field, and telephoto lens so the camera crew was out of range of the
shrapnel.

The microwave came apart like a soggy cardboard box - both the inner
compartment and outer casing.

** Here it is:

https://www.youtube.com/watch?v=IBfCUi494Sc

The fact that Champaign bottles are very strong and the cork is capped & wired down allows the pressure to build up an enormous level.

Mythbusters did something similar with modified electric hot water systems, launching them hundreds of feet in the air.


..... Phil

 

[Ian Field]

"F Murtz" <haggisz@hotmail.com> wrote in message
news:56aebe93$0$24106$c3e8da3$460562f1@news.astraweb.com...

~misfit~ wrote:
Once upon a time on usenet F Murtz wrote:
~misfit~ wrote:
Once upon a time on usenet Ian Field wrote:
"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:n8ejm7$c5k$1@dont-email.me...
Once upon a time on usenet Trevor Wilson wrote:
On 29/01/2016 11:31 AM, ~misfit~ wrote:
Once upon a time on usenet Ian Field wrote:
"~misfit~" <shaun.at.pukekohe@gmail.com> wrote in message
news:n8bron$52f$1@dont-email.me...
Once upon a time on usenet Ian Field wrote:
"Trevor Wilson" <trevor@SPAMBLOCKrageaudio.com.au> wrote in
message news:dgsp74Fic3lU1@mid.individual.net...
On 27/01/2016 5:25 PM, Robert wrote:

"Phil Allison" <pallison49@gmail.com> wrote in message
news:66bfb608-92ae-411f-8577-ab9dcd398235@googlegroups.com...
Robert wrote:
"Phil Allison"

** Potentially, it can cause arcing in the wave guide
leading to the > oven enclosure. Then a fuse blows.

However, most microwave ovens are immune from the effect,
but makers > still advise never to do it.

I happen to own one that isn't immune, a Samsung MB245.

I cannot use it to thaw a frozen bottle of lemonade, or
it arcs up.

Mine is a new Samsung ME73M.

What do you mean by 'arc up' ?


** A few seconds after the oven is switched on, a visible
and audible arc starts up at the top of the wave guide -
just behind the mica window. It quickly burns the paint in
that area and the oven must be switched off immediately.


I did hear a loud sound as soon as I switched the oven on
while empty, which is the first time I switched it on. I
wouldn't be surprised if the oven is damaged from what I
did. It seems crazy that just having the oven for a few
seconds
could damage it.

**Well, you're feeding something like 1.5kW into the MO, most
of which ends up being used by the magnetron. The energy has
to be dissipated somewhere. Where do you think all that
energy should go?

Drawing that much power from the mains usually only gets you
about 700 - 800W of cooking power. Half of it produces heat
anyway. Apparently the potential for damage is in standing
waves and reflections within the cooking compartment. There's
usually some form of pin-bearing light alloy vanes to scatter
the beam and constantly vary the "mode" - so its pretty
random anyway whether the waves will be reflected directly
back into the waveguide. With a big fat turkey in there, all the
waves get absorbed -
in theory anyway.

Interesting thread. My thanks to the contributers, I learned a
lot about microwave ovens.

There's a TV programme called; Brainiac - Science Abuse.

The decided to microwave a bottle of Champaign.

They used a portable generator so they could run the microwave
in the middle of a field, and telephoto lens so the camera crew
was out of range of the shrapnel.

The microwave came apart like a soggy cardboard box - both the
inner compartment and outer casing.

I've never liked the sort of show that tries to drag in viewers
with sensationalism - I often find them insubstantial, catering
to the lowest common denominators in the audience they pull with
their title and previews of explosions.

That said if both you and Trevor watch it I might grab a few
shows from somewhere and check it out - I could likely put up
with that presentation style if I'm learning stuff.


**Some of the shows were pretty ordinary, but the presentation
style is hugely amusing.

Thanks for the further input. I have an odd sense of humour. A
large amount of what /most/ people find amusing I find boorish and
juvenile. (I haven't wathced TV 'comedy' in a dog's age.) I know,
I'm a freak.
Watching someone run on a pool full of custard was
a hoot.

Ahh, a demonstration of a dilatant substance? Coincidentally just
last week I used the term to explain to a friend how I knew that
the slurry coating of McDonalds fry-pies is cornflour based.

If you mix up some corn starch and put it in an ultrasonic cleaner;
it rises up like vertical tendrils.

Interesting. However I don't have an ultrasonic cleaner so....

I do will it hurt it?

From what I know about the devices it would be best to put some
cornflour
paste into a small bowl - perhaps a yoghurt container or similar and
float
that in the liquid in the cleaner rather than putting it in directly.

I have had it for about 5 years, bought it on special on impulse, have
never used it,

The proper industrial small bench top ultrasonic cleaners would take it in
their stride - but not many people pay those prices.

The cheap Ł15 ones found in discount stores might struggle a bit.