David Lesher writes:

James Sweet writes:



I've never seen one with a ferro-resonant transformer. They use a
standard laminated core power transformer with a pair of magnetic shunts
to regulate the current.

[Johnny Carson voice] "I did not know that...."

All I've ever had to a u-w power supply was to replace the rectifier
stack; or junk the oven because it was clearly smoked...

Someone one mentioned they were F-R, and a casual look seemed to confirm
that, so I never questioned it. A F-R is also current limited; short the
output and it delivers rated current, period..

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

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Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

On Fri, 30 May 2008 01:50:29 GMT, (Fiat Sparks) wrote:

Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/


Don't try to operate that oven from a cheap generator with a less than perfect
sine output. That's another excuse for the blue smoke to leak out. BTDT.

In my case I wasn't about to spend that kind of money to repair an oven that
barely cost that much, especially since I used it in my restaurant always on
high. Therefore I yanked out all those fancy electronics and installed the
transformer/diode/cap assembly from another old oven. I drilled a hole
through that nice touch pad and installed an Intermatic spring-wound timer
from Home Depot.

Viola, good as new and bullet-proof against nasty power.

John

--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com -- best little blog on the net!
Tellico Plains, Occupied TN
The secret to creativity is knowing how to hide your sources -Albert Einstein

(Fiat Sparks) writes:

Sam Goldwasser wrote:

Never seen an FR uwave. Why would they use that when the basic
circuit is adequate and reliable (more or less!)?

Mostly less! :-) My Panasonic inverter unit just released the magic

Sorry, I was referring mostly to the normal transformer/capacitor/diode
circuit.

smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

I finally did find a service manual...in spanish (which I read
poorly,) but it did at least tell me what all the small resistors and
diodes were supposed to be (before they melted.)

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/



--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

(Fiat Sparks) writes:

Mostly less! :-) My Panasonic inverter unit just released the magic
smoke. First the magenetron died, and then after I replaced that, an
IGBT in the switcher shorted and did a fair bit of collateral damage.

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.

(On the Panasonic, settings of "1" and "2" actually run the magnetron at
30% power, using 1/3 and 2/3 on time).

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

Dave

(Dave Martindale) wrote in news:g1pa8d$ljv$2
@swain.cs.ubc.ca:

Conventional microwaves set to "3" run the magnetron about 4.5 seconds
at full power followed by about 10.5 seconds off, and 4.5 seconds of
full power into a single egg generates enough steam for an explosion.



Saw something in a catalogue: a plastic 'Egg' shaped chamber that holds 4
eggs and some water. I am guessing that it is a 'plastic pressure cooker'.
Anyway, they claim you can hard boil eggs in it in a microwave oven.



--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

(Dave Martindale) wrote:

Ouch. We have one that's only a few months old; I hope it does better
than that. I love it because all of the power settings from "3" to "10"
actually vary the magnetron RF output while keeping it on continuously.
At "3", I can cook a single egg in the oven without it exploding.

Mine lasted about eight years with daily use for a family of 5. So,
hopefully you've got a ways to go. I agree, it does cook nicely, which
is why I even bothered to repair it.

So, $100 in parts later, I now have a working microwave again. And, if
I get tired of it, I can sell it on Craigslist for at least $35! :-/

For that much, I'd be tempted to scrap it and buy a new oven.

You know, that's what the wife said! :-)

Had I known it was going to go out again after the magenetron died, I
probably would have. But, my pride was at stake!