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

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?


** Do NOT even dream of fixing your own microwave oven.

The devices are ABSOLUTELY LETHAL !!



..... Phil

On 4/3/2013 23:06, 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

Bad triac?

Microwave ovens have a vacuum tube. If you have a bad tube, or no
filament power, the transformer will hum and no heat is produced.
New microwave ovens aren't a lot more expensive than new tubes
and the labor to put 'em in.

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

Could be a bad heater in the magnetron, or the HV doubler is bad.

I'd not suggest opening a microwave oven for repairs unless you are
familiar with handling the high voltage cap in them. They seem to be the
perfect rating to electrocute folks.

If you're past that, and know how to dischard the filter cap, turn on the
oven and check the HV output of the doubler, it should be around 4kV.

If that's good, check the heater coil of the magnetron, it should appear
to be a short. Check the filament winding on the transformer too. It's
more likely to have bad crimp connections than being burned out, but you
never know.

A fairly detailed (even overly detailed) microwave oven FAQ is here

http://repairfaq.ece.drexel.edu/REPA...tml#MICFAQ_008

Anyways, if the cap or rectifier are bad, it's worth $15 and a trip to
ebay for replacements. They're all pretty generic and the chinese junk off
there is no worse than they build new microwaves with anyways.

If anything else is bad, it's just not worth fixing unless you want to
make a project out of it.

"Cydrome Leader" wrote in message
...
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

Could be a bad heater in the magnetron, or the HV doubler is bad.

I'd not suggest opening a microwave oven for repairs unless you are
familiar with handling the high voltage cap in them. They seem to be the
perfect rating to electrocute folks.

If you're past that, and know how to dischard the filter cap, turn on the
oven and check the HV output of the doubler, it should be around 4kV.

If that's good, check the heater coil of the magnetron, it should appear
to be a short. Check the filament winding on the transformer too. It's
more likely to have bad crimp connections than being burned out, but you
never know.

A fairly detailed (even overly detailed) microwave oven FAQ is here

http://repairfaq.ece.drexel.edu/REPA...tml#MICFAQ_008

Anyways, if the cap or rectifier are bad, it's worth $15 and a trip to
ebay for replacements. They're all pretty generic and the chinese junk off
there is no worse than they build new microwaves with anyways.

If anything else is bad, it's just not worth fixing unless you want to
make a project out of it.


Worth just checking that nothing has come adrift mechanically to block the
waveguide ? I have this dim recollection of something along those lines
happening to a cheapo one that we once owned some years back

Arfa

"Tom Kupp"

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?


Bad triac?


*** If the unit had a faulty triac ( most use relays ) then the transformer
would either:

1. Not hum at all.

2. Blow the supply use immediately.


.... Phil

Arfa Daily wrote:


"Cydrome Leader" wrote in message
...
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

Could be a bad heater in the magnetron, or the HV doubler is bad.

I'd not suggest opening a microwave oven for repairs unless you are
familiar with handling the high voltage cap in them. They seem to be the
perfect rating to electrocute folks.

If you're past that, and know how to dischard the filter cap, turn on the
oven and check the HV output of the doubler, it should be around 4kV.

If that's good, check the heater coil of the magnetron, it should appear
to be a short. Check the filament winding on the transformer too. It's
more likely to have bad crimp connections than being burned out, but you
never know.

A fairly detailed (even overly detailed) microwave oven FAQ is here

http://repairfaq.ece.drexel.edu/REPA...tml#MICFAQ_008

Anyways, if the cap or rectifier are bad, it's worth $15 and a trip to
ebay for replacements. They're all pretty generic and the chinese junk off
there is no worse than they build new microwaves with anyways.

If anything else is bad, it's just not worth fixing unless you want to
make a project out of it.


Worth just checking that nothing has come adrift mechanically to block the
waveguide ? I have this dim recollection of something along those lines
happening to a cheapo one that we once owned some years back

Arfa

I promised to count the number of screws on my old (1981) samsung
microwave oven. This was back when they were overbuilt. There's actually
20 stainless torx screws in the front door inner bezel just to hold the
glass in place. It's amazing.

I promised to count the number of screws on my old (1981)
Samsung microwave oven. This was back when they were
overbuilt. There's actually 20 stainless torx screws in the
front door inner bezel just to hold the glass in place. It's amazing.

Could their purpose have been to hold the screen so firmly in place that it
could not come loose and permit leakage?

William Sommerwerck wrote:
I promised to count the number of screws on my old (1981)
Samsung microwave oven. This was back when they were
overbuilt. There's actually 20 stainless torx screws in the
front door inner bezel just to hold the glass in place. It's amazing.

Could their purpose have been to hold the screen so firmly in place that it
could not come loose and permit leakage?

the screen is behind the glass, or sheets of glass, where would it even
slip or go? It's not like 20 screws will hold a piece of glass all that
much flatter than 10. I've seen autoclaves with wimpier doors.

Has anybody ever come across a microwave oven that actually has microwave
leakage out the front door or gaskets? We always did the testing, but
never had a reject or a loose door.

"Cydrome Leader" wrote in message ...
William Sommerwerck wrote:

I promised to count the number of screws on my old (1981)
Samsung microwave oven. This was back when they were
overbuilt. There's actually 20 stainless torx screws in the
front door inner bezel just to hold the glass in place. It's amazing.

Could their purpose have been to hold the screen so firmly in
place that it could not come loose and permit leakage?

The screen is behind the glass, or sheets of glass, where would
it even slip or go?

Could the /glass/ slip?

The question is /plausible/ in the context that Samsung wouldn't waste time
and money installing screws it didn't think were necessary. (See following.)


Has anybody ever come across a microwave oven that actually
has microwave leakage out the front door or gaskets? We always
did the testing, but never had a reject or a loose door.

Back in the 70s (I think) the Government set emissions standards. I remember
an Amana commercial (I'm watching "Perry Mason" as I write this -- why
couldn't Barbara Hale have been my mother? Of course, then I would have been
William Katt.) in which a large, sharp-edged weight was slammed against the
oven, leaving a huge gash. Amana claimed that, even with this damage, the oven
still met emissions specs.

William Sommerwerck wrote:
"Cydrome Leader" wrote in message ...
William Sommerwerck wrote:

I promised to count the number of screws on my old (1981)
Samsung microwave oven. This was back when they were
overbuilt. There's actually 20 stainless torx screws in the
front door inner bezel just to hold the glass in place. It's amazing.

Could their purpose have been to hold the screen so firmly in
place that it could not come loose and permit leakage?

The screen is behind the glass, or sheets of glass, where would
it even slip or go?

Could the /glass/ slip?

The question is /plausible/ in the context that Samsung wouldn't waste time
and money installing screws it didn't think were necessary. (See following.)


Has anybody ever come across a microwave oven that actually
has microwave leakage out the front door or gaskets? We always
did the testing, but never had a reject or a loose door.

Back in the 70s (I think) the Government set emissions standards. I remember
an Amana commercial (I'm watching "Perry Mason" as I write this -- why
couldn't Barbara Hale have been my mother? Of course, then I would have been
William Katt.) in which a large, sharp-edged weight was slammed against the
oven, leaving a huge gash. Amana claimed that, even with this damage, the oven
still met emissions specs.

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 just instantly dissolves the paper bag you
were holding just seconds earlier.

If there were strict standards back then, I doubt anbody is testing them
anymore. Those cone shaped Simpson probes were the rage, then there were
the taiwanese cheapo VU meter attached to a diode and a loop of wire
leakage meters. Again, I've never seen any of them ever register anything.

Even the Amana and Tappan units didn't have thousands of screws holding
them together. I've always been really curious about how this oven was
designed or who it was copied from in the first place.

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.


Even the Amana and Tappan units didn't have thousands of
screws holding them together. I've always been really curious
about how this oven was designed or who it was copied from.

It's possible all those screws were needed to compensate for sloppy
tolerances. But without tearing it apart, there's no way to know.

"Cydrome Leader" wrote in message
...
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

Could be a bad heater in the magnetron, or the HV doubler is bad.

I'd not suggest opening a microwave oven for repairs unless you are
familiar with handling the high voltage cap in them. They seem to be the
perfect rating to electrocute folks.

If you're past that, and know how to dischard the filter cap, turn on the
oven and check the HV output of the doubler, it should be around 4kV.


Not many people have a meter fit for measuring 4kV, and its pretty dangerous
even for someone experienced with repairing microwaves!

The transformer secondary feeds 2kVAC to the doubler at enough current to
easily guarantee lethality, and even when its switched off there's a hefty
capacitor can give you a nasty belt!

I've heard tell of an apprentice left mucking about drawing sparks with the
tip of a screwdriver while his boss went out to the van for a part - when
the boss returned the apprentice was laying dead on the floor - the
screwdriver had a cracked handle!

As for the fault with the transformer humming but not much else, the
magnetron tube can lose emission (especially if you defrost a lot) or the
heater can go O/C.

IWHT any bad crimps around the secondary side would arc noisily - but not in
the low voltage heater circuit (be sure to discharge the capacitor before
delving in to investigate!).

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.

A slightly odd one came in when I used to repair the things - the fuse had
blown, and a replacement had it going again like nothing had happened, the
usual inspection of the interlock micrswitches showed nothing amis (they
sometimes weld intermittently if the user slams the door a lot) Eventually I
discovered a "pimple" on the capacitor casing - obviously a minor explosion
had occurred between the layers of foil in the capacitor and the flying
debris had dented the can, apparently the capacitor had "self-healed" and
was ready to go once a new fuse had been fitted. Playing safe; I replaced
the capacitor before wrapping up the job.

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 liked the ones that opened like oven doors. The last tappan around here
died when the mechanical timer wore out.

Even the Amana and Tappan units didn't have thousands of
screws holding them together. I've always been really curious
about how this oven was designed or who it was copied from.

It's possible all those screws were needed to compensate for sloppy
tolerances. But without tearing it apart, there's no way to know.

Interesting point. Maybe the glass is what holds the door together.

I'm going to have to take the thing apart. The thing is guest-proof too.
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'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.

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.


Couldn't aggree more. When my mehanical timer microwave went a few
years back I went around to the 4 or 5 different microwave ovens at
work to find the one that was simplest to use, then bought a very
similiar one of the same brand. Key in time, hit start.

Jerry

On Apr 6, 3:21*pm, Jerry Peters wrote:
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.

Couldn't aggree more. When my mehanical timer microwave went a few
years back I went around to the 4 or 5 different microwave ovens at
work to find the one that was simplest to use, then bought a very
similiar one of the same brand. Key in time, hit start.

* * * * Jerry

But you're robbing the design engineers the opportunity to demonstrate
how complicated a system they can design just to heat a bowl of soup.

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 advangage 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


--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

"Leif Neland" wrote in message
...
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 advangage 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.


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.

Arfa



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


--
Husk kørelys bagpå, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

"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

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. :-)

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

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

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.

"Phil Allison" wrote in message
...

"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.

"William Sommerwerck" wrote in message
...
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.

Ian Field wrote:


"William Sommerwerck" wrote in message
...
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?

amdx 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?

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.

"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

On 4/4/2013 2:06 PM, 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

"Trevor Wilson" wrote in message
...
On 4/4/2013 2:06 PM, 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.

William Sommerwerck 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.

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


"Trevor Wilson" wrote in message
...
On 4/4/2013 2:06 PM, 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

Ian Field wrote:


"Trevor Wilson" wrote in message
...
On 4/4/2013 2:06 PM, 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" wrote in message ...
William Sommerwerck 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.

William Sommerwerck wrote:
"Cydrome Leader" wrote in message ...
William Sommerwerck 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?

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?

"Cydrome Leader" wrote in message
...
Ian Field wrote:


"Trevor Wilson" wrote in message
...
On 4/4/2013 2:06 PM, 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.