GE Microwave JVM1540DM3WW Everything but Heat

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

 

[Phil Allison]

<kflook67@gmail.com>

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

 

[Tom Kupp]

On 4/3/2013 23:06, 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

Bad triac?

 

[whit3rd]

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.

 

[Cydrome Leader]

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

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/REPAIR/F_micfaq5.html#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.

 

[Arfa Daily]

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:kjkvtb$hd$1@reader1.panix.com...

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

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/REPAIR/F_micfaq5.html#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

 

[Phil Allison]

"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

 

[Cydrome Leader]

Arfa Daily <arfa.daily@ntlworld.com> wrote:

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:kjkvtb$hd$1@reader1.panix.com...
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

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/REPAIR/F_micfaq5.html#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.

 

[William Sommerwerck]

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?

 

[Cydrome Leader]

William Sommerwerck <grizzledgeezer@comcast.net> 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.

 

[William Sommerwerck]

"Cydrome Leader" wrote in message news:kjmsck$nfl$1@reader1.panix.com...
William Sommerwerck <grizzledgeezer@comcast.net> 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]

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.

 

[Ian Field]

"Cydrome Leader" <presence@MUNGEpanix.com> wrote in message
news:kjkvtb$hd$1@reader1.panix.com...

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

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.

 

[Cydrome Leader]

William Sommerwerck <grizzledgeezer@comcast.net> wrote:

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

 

[William Sommerwerck]

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.

 

[Cydrome Leader]

William Sommerwerck <grizzledgeezer@comcast.net> 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.

 

[Jerry Peters]

William Sommerwerck <grizzledgeezer@comcast.net> 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

 

[hrhofann@sbcglobal.net]

On Apr 6, 3:21 pm, Jerry Peters <je...@example.invalid> wrote:

William Sommerwerck <grizzledgee...@comcast.net> 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.

 

[Leif Neland]

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 křrelys bagpĺ, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.

 

[Arfa Daily]

"Leif Neland" <leif@neland.dk> wrote in message
news:mn.3aef7dd4e0b0753c.130671@neland.dk...

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 křrelys bagpĺ, hvis din bilfabrikant har taget den idiotiske
beslutning at undlade det.