Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old June 18th 20, 06:45 AM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

On 18/06/2020 09:50, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:

[...]
I'd follow these steps too, but I also have the test equipment for doing
so, but OP says they have an inverter microwave. That should scratch the
#2s off the list, which is really easy for for a traditional half-doubler
microwave oven. They have no way to test the HV section safely. Microwaves
are truly the most dangerous electronic appliances to play with.


If you don't know what you're doing, don't have sufficient experience,
can't follow advice, and are afraid of high voltage, perhaps you
really shouldn't be fixing microwave ovens?


It is worthwhile pointing out, at every opportunity, that the electric
shock hazard of working on microwave ovens is extreme, and that
rigourous precautions are necessary. No other appliance that I can think
of has the combination of high enough voltage to shock severely through
clothing and dry skin, enough current to certainly kill someone, yet
some current limiting and isolation from the mains such that a RCD or
circuit breaker will not trip to save you.

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Old June 18th 20, 08:08 AM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:

Jeff Liebermann wrote:
On Mon, 8 Jun 2020 00:02:34 +0100, Andrew wrote:

Hi, I have an NN-A554W and the transformer on the inverter board has
blown. Microwave wouldn't start cooking so I ran it for a moment with
the cover off, transformer did a light and smoke display and now it
smells like fireworks.

Impressive. I know how you feel:
http://www.learnbydestroying.com/jeffl/pics/drivel/#burned-yam.jpg
That's what happened when I cooked a yam (potatoe) for 16 minutes
instead of 6 minutes. It was glowing bright red inside just before I
opened the door. The inside of my Panasonic NN-S533WF (Sensor 1300w)
microwave oven changed from white to yam colored. I tried to clean
it, but the yam color is permanently baked into the paint. The S/N
label says made in 2003. I think I received it as a present in 2005,
making it 15 years old. It works as well today as it did in 2005 with
no change in output level. That's one of the benefits of an inverter
oven.


Lol, I've wondered about the "sensor" in these things. I know can't be
related to any sort of device that measures anything. Must be marketing
speak or a weirdly translated word.


It's a humidity sensor. When whatever you're cooking gets hot enough
to vaporize water, the "sensor" detects the water vapor and shuts off
the oven, usually after a short delay. The alleged advantage is that
you don't need to enter the cooking time or power level, but you do
need to enter the type of food:
https://www.youtube.com/watch?v=__tYa70kRHY
I've only used the sensor feature a few times. No opinion on whether
it's useful, or yet another useless feature.

I used it couple times years ago. It may also function when using slower
cooking mode, not sure. My display gets dimmer and foggy but keeps on
working.

Greg

I'd follow these steps too, but I also have the test equipment for doing
so, but OP says they have an inverter microwave. That should scratch the
#2s off the list, which is really easy for for a traditional half-doubler
microwave oven. They have no way to test the HV section safely. Microwaves
are truly the most dangerous electronic appliances to play with.


If you don't know what you're doing, don't have sufficient experience,
can't follow advice, and are afraid of high voltage, perhaps you
really shouldn't be fixing microwave ovens?

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Old June 18th 20, 02:26 PM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

Cydrome Leader wrote:
Say there is a moisture detector in ther sniffing the air being pulled
from the cavity. It doesn't prevent a frozen pot pie from burning, it
doesn't prevent anything from overcooking. It doesn't seem to know when a
frozen sausage is transitioning from thawing to outright cooking. I really
have no idea what it's doing. It's too mysterious to take seriously.
Really old microwaves sometimes had the temperature probe- that made
sense, assuming you were into cooking a turkey in the microwave oven for
30 minutes.


I had one of those in the shop at Clybourn, the probe had a 1/4" jack which
plugged into the interior wall. Was made by Sharp. Never used the probe
though.

Only reason I mention it is because I bought that from a store that only
sold microwave ovens. Nothing else, just microwave ovens and cookware for
microwaves. Guess those died out with laserdisc stores.

Say it's real. Do the just modulate the cooing duty cycle? It doesn't seem
to speed up or slow anything down, ot at least I've not found a mode that
isn's still time based.

What were the delicious things you could pull off with the sensor as sous
chef that just don't work with the magic chef?


Well, I only used it for reheating leftovers. Things like yesterdays mashed
potatoes or vegs (corn, peas or string beans) would come out evenly cooked
(hot all the way through) and not over cooked. When I tried the mashed in the
Magic Chef, I figured 2 minutes at full power would be enough being it only
takes 3 minutes to cook from the fridge but no, was cold in the middle.

I'm not saying the reheat mode with moisture detection is an end-all
solution but it worked correctly most of the time. Several times I put
something in there and it just didn't work, after 3 minutes or so it would
beep with "Sensor failure" on the display panel. Then it did a 30 second
countdown and end.

Even things like a leftover half corned beef sandwich came out good.

The sensor/reheat function just eliminated the guess work for time and duty
cycle (power level). It just gets you into the ballpark.

Any parted out ones on ebay? No real need for "new" as long as it works.


I didn't see anything but since I'd starve around here with a microwave I
didn't put a lot of effort in besides the appliance parts places on the web.
Home Depot (cash and carry, no delivery schedule to mess with) basically had
only 3 in stock, 2 of the Magic Chef and one Panasonic for double the price.
Since I plan on replacing the overhead one at some point soon, I just didn't
see a reason to spend the money on the Panasonic (although it did have a
sensor).

I was approached with a friend asking how to fix their above range
microwave oven too. I want to help, but until they can read me the model #
off the door, I can't do much with suggestions on what the next move is.


If you are bored mine is a JVM1653WH01 but I don't think it's wise to put
that much money into a 16 year old unit. The control board for a similar
vintage dishwasher that went out a couple years ago was fetching $150 and
up, used. Being I replaced the whole thing with a brand new one for a little
over $300 (and no interest for 12 months), whats the point.

One weird thing about that microwave which I mentioned once on chi.general,
when you set the time, the first entry it wants is the month, day and year.

Now being there is no advanced timer like putting in a potato and telling it
to cook it this saturday at 4pm (or a year from this saturday), you figure
the mm/dd/yy would be for the daylight savings switch.

But no, even before they changed the dates for dst/std, it never would
adjust the time by itself. Weird.

-bruce


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Old June 18th 20, 03:22 PM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

On 18/6/20 9:50 am, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:
Lol, I've wondered about the "sensor" in these things. I know can't be
related to any sort of device that measures anything. Must be marketing
speak or a weirdly translated word.


It's a humidity sensor. When whatever you're cooking gets hot enough
to vaporize water, the "sensor" detects the water vapor and shuts off
the oven, usually after a short delay.


The vapor pressure of water rises very rapidly above 60 degrees C.
So presence of vapor is a good indicator of the outside temperature of
your food, even before the water starts to boil.

CH
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Old June 18th 20, 07:10 PM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

On Thu, 18 Jun 2020 23:22:57 +1000, Clifford Heath
wrote:

On 18/6/20 9:50 am, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:
Lol, I've wondered about the "sensor" in these things. I know can't be
related to any sort of device that measures anything. Must be marketing
speak or a weirdly translated word.


It's a humidity sensor. When whatever you're cooking gets hot enough
to vaporize water, the "sensor" detects the water vapor and shuts off
the oven, usually after a short delay.


The vapor pressure of water rises very rapidly above 60 degrees C.
So presence of vapor is a good indicator of the outside temperature of
your food, even before the water starts to boil.

CH


Yep, but there's a little more to it. The 1978 Panasonic patent
agrees that it's the surface temperature that's important.
"Apparatus for controlling heating time utilizing humidity sensing"
https://patents.google.com/patent/US4097707
See "Description" section:
...it has been known to sense the temperature of the food
or degree of heating by measuring the change of humidity
which takes place as the food is heated. For example, in
most foods, water included therein abruptly evaporates
when the temperature of the food reaches 100 C and a
large amount of water vapor appears in the oven. By
detecting such change of humidity by a humidity sensor,
the time at which the humidity abruptly changes can be
related to the time at which the food has reached 100 C.

Further down the "Description" section, the patent explains how the
cooking time is extrapolated from the 100 C point and the target
temperature. Apparently, the humidity sensor is only interested in a
single point, where the air abruptly transitions from low humidity to
high humidity at 100 C. Everything else is done by temperature curve
extrapolation. Crude, but effective.





--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


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Old June 23rd 20, 04:50 AM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

Jeff Liebermann wrote:
On Thu, 18 Jun 2020 23:22:57 +1000, Clifford Heath
wrote:

On 18/6/20 9:50 am, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:
Lol, I've wondered about the "sensor" in these things. I know can't be
related to any sort of device that measures anything. Must be marketing
speak or a weirdly translated word.

It's a humidity sensor. When whatever you're cooking gets hot enough
to vaporize water, the "sensor" detects the water vapor and shuts off
the oven, usually after a short delay.


The vapor pressure of water rises very rapidly above 60 degrees C.
So presence of vapor is a good indicator of the outside temperature of
your food, even before the water starts to boil.

CH


Yep, but there's a little more to it. The 1978 Panasonic patent
agrees that it's the surface temperature that's important.
"Apparatus for controlling heating time utilizing humidity sensing"
https://patents.google.com/patent/US4097707
See "Description" section:
...it has been known to sense the temperature of the food
or degree of heating by measuring the change of humidity
which takes place as the food is heated. For example, in
most foods, water included therein abruptly evaporates
when the temperature of the food reaches 100? C and a
large amount of water vapor appears in the oven. By
detecting such change of humidity by a humidity sensor,
the time at which the humidity abruptly changes can be
related to the time at which the food has reached 100? C.

Further down the "Description" section, the patent explains how the
cooking time is extrapolated from the 100? C point and the target
temperature. Apparently, the humidity sensor is only interested in a
single point, where the air abruptly transitions from low humidity to
high humidity at 100? C. Everything else is done by temperature curve
extrapolation. Crude, but effective.


Hmm, sort of shocked there wasn't a "fuzzy logic" spin on all of that in
1988 or whenever that annoying as hell fad came out.
  #27   Report Post  
Old June 23rd 20, 04:57 AM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

Chris Jones wrote:
On 18/06/2020 09:50, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:

[...]
I'd follow these steps too, but I also have the test equipment for doing
so, but OP says they have an inverter microwave. That should scratch the
#2s off the list, which is really easy for for a traditional half-doubler
microwave oven. They have no way to test the HV section safely. Microwaves
are truly the most dangerous electronic appliances to play with.


If you don't know what you're doing, don't have sufficient experience,
can't follow advice, and are afraid of high voltage, perhaps you
really shouldn't be fixing microwave ovens?


It is worthwhile pointing out, at every opportunity, that the electric
shock hazard of working on microwave ovens is extreme, and that
rigourous precautions are necessary. No other appliance that I can think
of has the combination of high enough voltage to shock severely through
clothing and dry skin, enough current to certainly kill someone, yet
some current limiting and isolation from the mains such that a RCD or
circuit breaker will not trip to save you.


That's a good point too. All the service tech microwave oven deaths in the
US I'm aware of were people getting dead from the capacitor, with the unit
off. apparently those caps are perfectly sized to just stop your heart.
You'd get noticed about who croaked last in the trade bulletin/sales
"newsletters" that got mailed out every few months.

No doubt if you were getting electrocuted off a running microwave, the
fuse would never blow. I have a large transformer for what I'm told is an
industrial microwave something device. The transformer doesn't even have
shunts and outputs a full 4kV at a couple kW. It makes for one of the
fiercest jacob's ladders I've thrown together.

  #28   Report Post  
Old June 23rd 20, 05:06 AM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

wrote:
Cydrome Leader wrote:
Say there is a moisture detector in ther sniffing the air being pulled
from the cavity. It doesn't prevent a frozen pot pie from burning, it
doesn't prevent anything from overcooking. It doesn't seem to know when a
frozen sausage is transitioning from thawing to outright cooking. I really
have no idea what it's doing. It's too mysterious to take seriously.
Really old microwaves sometimes had the temperature probe- that made
sense, assuming you were into cooking a turkey in the microwave oven for
30 minutes.


I had one of those in the shop at Clybourn, the probe had a 1/4" jack which
plugged into the interior wall. Was made by Sharp. Never used the probe
though.

Only reason I mention it is because I bought that from a store that only
sold microwave ovens. Nothing else, just microwave ovens and cookware for
microwaves. Guess those died out with laserdisc stores.


Weird. Microwaves+? I think they rebranded Batteries+ into something
equally weird like batteries and CFL bulbs and +. There was one in a strip
mall on Clyborn by Armitage or someting like that.

Say it's real. Do the just modulate the cooing duty cycle? It doesn't seem
to speed up or slow anything down, ot at least I've not found a mode that
isn's still time based.

What were the delicious things you could pull off with the sensor as sous
chef that just don't work with the magic chef?


Well, I only used it for reheating leftovers. Things like yesterdays mashed
potatoes or vegs (corn, peas or string beans) would come out evenly cooked
(hot all the way through) and not over cooked. When I tried the mashed in the
Magic Chef, I figured 2 minutes at full power would be enough being it only
takes 3 minutes to cook from the fridge but no, was cold in the middle.

I'm not saying the reheat mode with moisture detection is an end-all
solution but it worked correctly most of the time. Several times I put
something in there and it just didn't work, after 3 minutes or so it would
beep with "Sensor failure" on the display panel. Then it did a 30 second
countdown and end.

Even things like a leftover half corned beef sandwich came out good.


Not trying to mess with you, but these sound easy enough to take care of
with even random presses of the quick minute button. Going to try an
"intelligent" mode for some frozen vegetables now in fact.

The sensor/reheat function just eliminated the guess work for time and duty
cycle (power level). It just gets you into the ballpark.

Any parted out ones on ebay? No real need for "new" as long as it works.


I didn't see anything but since I'd starve around here with a microwave I
didn't put a lot of effort in besides the appliance parts places on the web.
Home Depot (cash and carry, no delivery schedule to mess with) basically had
only 3 in stock, 2 of the Magic Chef and one Panasonic for double the price.
Since I plan on replacing the overhead one at some point soon, I just didn't
see a reason to spend the money on the Panasonic (although it did have a
sensor).

I was approached with a friend asking how to fix their above range
microwave oven too. I want to help, but until they can read me the model #
off the door, I can't do much with suggestions on what the next move is.


If you are bored mine is a JVM1653WH01 but I don't think it's wise to put
that much money into a 16 year old unit. The control board for a similar
vintage dishwasher that went out a couple years ago was fetching $150 and
up, used. Being I replaced the whole thing with a brand new one for a little
over $300 (and no interest for 12 months), whats the point.


Check the prices for the "computer board" for the new washer. Probably
$243 if you get a good price.

One weird thing about that microwave which I mentioned once on chi.general,
when you set the time, the first entry it wants is the month, day and year.

Now being there is no advanced timer like putting in a potato and telling it
to cook it this saturday at 4pm (or a year from this saturday), you figure
the mm/dd/yy would be for the daylight savings switch.

But no, even before they changed the dates for dst/std, it never would
adjust the time by itself. Weird.

-bruce


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Old February 23rd 21, 10:45 PM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

On Tuesday, June 9, 2020 at 8:19:30 AM UTC-4, Peter W. wrote:
1 (800) 211-7262

I entirely understand that this Group exists so that individuals may discuss means-and-methods for doing pretty much anything at all in the hardest possible way, reaching for the least satisfactory results. And that includes reaching around the world for S.W.A.G., anecdotal experiences and arbitrary suggestions.

Rather than going to the Mother Ship and asking there.

Panasonic Customer Service number above.

Then: https://www.justanswer.com/sip/panasonic-help-24-7?r=ppc|ga|27|Tech-CE-SQR-Search-BMM|CE-Panasonic|&JPKW=%2Bpanasonic%20%2Bengland&JPDC=S&J PST=&JPAD=378934176681&JPMT=b&JPNW=g&JPAF=txt&JPRC =1&JPCD=&JPOP=&cmpid=2032112328&agid=76054807163&f iid=&tgtid=kwd-807471796533&ntw=g&dvc=c&gclid=CjwKCAjw5vz2BRAtEiw AbcVIL4IpznzJVHkSJM0UAa4rerYc42_ibvjnkdsd_EkpKG39B sihtcQHsBoC1VcQAvD_BwE
Peter Wieck
Melrose Park, PA


If cost is an issue, then ... I don't know if I'm just hallucinating or not, but at the end of each calendar school year, many university and college dorms have small piles of ... wait for it ... microwave ovens (amongst other gadgets) piled high outside as students are moving out for the summer.
I don't exactly see armed guards surrounding those piles.
  #30   Report Post  
Old February 23rd 21, 11:35 PM posted to sci.electronics.repair
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Default Panasonic microwave, blown inverter board transformer

On Monday, June 22, 2020 at 10:57:49 PM UTC-4, Cydrome Leader wrote:
Chris Jones wrote:
On 18/06/2020 09:50, Jeff Liebermann wrote:
On Wed, 17 Jun 2020 06:55:26 +0000 (UTC), Cydrome Leader
wrote:

[...]
I'd follow these steps too, but I also have the test equipment for doing
so, but OP says they have an inverter microwave. That should scratch the
#2s off the list, which is really easy for for a traditional half-doubler
microwave oven. They have no way to test the HV section safely. Microwaves
are truly the most dangerous electronic appliances to play with.

If you don't know what you're doing, don't have sufficient experience,
can't follow advice, and are afraid of high voltage, perhaps you
really shouldn't be fixing microwave ovens?


It is worthwhile pointing out, at every opportunity, that the electric
shock hazard of working on microwave ovens is extreme, and that
rigourous precautions are necessary. No other appliance that I can think
of has the combination of high enough voltage to shock severely through
clothing and dry skin, enough current to certainly kill someone, yet
some current limiting and isolation from the mains such that a RCD or
circuit breaker will not trip to save you.

That's a good point too. All the service tech microwave oven deaths in the
US I'm aware of were people getting dead from the capacitor, with the unit
off. apparently those caps are perfectly sized to just stop your heart.
You'd get noticed about who croaked last in the trade bulletin/sales
"newsletters" that got mailed out every few months.

No doubt if you were getting electrocuted off a running microwave, the
fuse would never blow. I have a large transformer for what I'm told is an
industrial microwave something device. The transformer doesn't even have
shunts and outputs a full 4kV at a couple kW. It makes for one of the
fiercest jacob's ladders I've thrown together.


I don't know about anywhere else in the world, but in the U.S., there's a dire warning of death with any product you buy, including a Happy Meal. Because of the fear of lawyers, every product gets warning labels no matter how sill it is, so people are now conditioned to totally ignore warnings. Pick up a can of spray paint. The instructions take up 2/3 of the can, and 9/10s of that is warnings of some type.

But yes, microwaves are uniquely qualified to end someone's life. To those who don't know, microwave ovens seem less dangerous than a TV or stereo receiver, so how could they hurt someone?

So, to anyone reading this that is thinking about repairing their microwave: BE CAREFUL. MORE THAN ANYTHING ELSE IN YOUR HOUSE, A MICROWAVE IS CAN KILL YOU EVEN WHEN IT'S UNPLUGGED!


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