New microwave: inverter?

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jeffg

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We need a over-the-range microwave and were looking at the Panasonics. If anyone has one, does their inverter technology make much difference in the real-world, I mean apart from the usual marketing hype. :) I read something not long ago about increased magnetron failures on these models, is that true?

Our oven cavity is fairly shallow, we're limited to 16" depth which rules out the best Panasonic models (which are almost 20"D). So if the inverter doesn't matter we'd prefer to go with another brand that fits better. :)

Thanks again!!
 
Good and Cheap!

Here's what I presently own as a driver. I have a couple of vintage Radaranges, but the bottoms of my wall cabinets are so close to my countertop I cannot use the Amanas right now; they're too tall, so they're stored downstairs. Plus the RR-4D needs some work.

What I have is a Magic Chef MCM1110ST, which is a 1000-watt unit. It's mostly black with some stainless trim on the front, and a nicely designed chrome handle for the door. It feels more solid than a lot of today's microwaves, and it looks reasonably upscale; it does not have that cheap, "door buster" look of many inexpensive units. It's one of the few non-vintage things visible in my kitchen, and it coordinates well with my black-and-chrome collectible stuff.

Mine has done everything I've asked of it. It's an even-cooking unit, and the controls are intuitive. It runs about $110 at average retail; Amazon, Best Buy and Walmart all carry it.

A photo and a link to the Magic Chef product page are below.


danemodsandy++10-12-2013-16-45-38.jpg
 
Junk . . .

In my experience the Panasonics cook OK but the quality of the rest is barely above junk. In the last 5 years I've thrown two away because of problems. In the first one a tiny plastic tab in the door assembly broke that holds the latch spring. There are no electronics in the door, it was purely a mechanical problem. I managed to figure another way to mount the spring top and the oven worked for another year or two until one day I opened the door when it was running, reached my hand in and realized it had failed to automatically turn off. Needless so say I removed my hand quickly. The timer had also gone wonky so I assume it had to do with a bad IC chip or something.

 

The second one worked fine for a little more than a year at which point it often failed to turn on unless you slammed the door. After awhile this became so annoying - you had to slam it hard enough to hear it throughout the house - that we just ditched it for a GE. I might add this is an adult household of two people who once had a Radarange last 17 years, so we're not abusers.
 
Have A Panasonic Genius 1300w with "Inverter"

Purchased second hand after our older Sharp micro gave out, and totally love the thing. You can search the archives for our posts relating to the Sharp and subsequent purchase of the Panasonic.

Needed a new microwave right away and as someone in the area was selling a nearly NIB Panasonic for dirt cheap money, picked it up instead of purchasing new.

What one loves about the Panasonic is not having to turn things over when say defrosting and or cooking. Everything comes out "done" and just so buy just placing things in the oven and then using whatever pre-programmed setting or doing things on the fly.

From what one understands rather than cycling off and on full power like most microwaves, the inverter technology allows full use of whatever percentage of power is requested. If you choose "50%" of power, that is what you get, constant. The various cycles move between whatever settings have been pre-programmed.

My unit has sensors as well so again everything comes out well between that and the Inverter tech. Sometimes reheating really dense things like turkey breasts or drumsticks even when set to "more" and using "Sensor Reheat" are still not fully evenly heated. One has learned to either pop things back in for a while or just to set the proper power level and use a timed cycle.
 
I think your problems were related to the door latch switch. We replaced one on an older (1980) non-inverter Panasonic and they're beyond cheap. Our symptoms were similar to yours (unit not recognizing that the door was closed, the oven staying on with the door open(!) etc). The switch is almost entirely cheap plastic and every slam of the oven door is another nail in its coffin. It doesn't take many nails.

Our unit was out of warranty and Panasonic wanted a hundred and something to fix it, we found the switch ourselves for $4 (easy to replace, not easy to find for purchase) and it ran for another 10 years before the new switch failed. Regardless of these problems it's been a great oven. We still have it, it still runs great and cooks very evenly.
 
Inverter Power

 
The main thing I *hate* about my GE Profile OTR unit (other than that it's OTR) is the power profiles.  The cycling is too long.  If set for 1 minute at 50% for example, it kinda mostly runs the magnetron for 30 seconds on then 30 seconds off (maybe not that bad, but close enough).  I have to either cover *everything* when reheating, or cut down to 30% or 40% power to avoid explosions.  None of my previous microwaves were so bad about causing messy explosions when reheating.

I'm assuming the inverter power method is more graceful.
 
Kenmore

I currently have a Kenmore Sensorwave OTR unit. It is a smooth operator and doesn't cycle the magnetron tube to achieve lower power levels. It is about to be replaced with a GE Advantium unit.

We had a Panasonic unit at work. It self destructed one day and has been replaced with Whirlpool ovens.

Malcolm
 
Panasonic used to make some decent stuff (I really like some of their 1970s stuff, it was nothing fancy but they had nice design and features) but not anymore... The only "newer" thing I have seen from them that hasn't experienced an early failure is a 10-15 years old GAOO TV set that a friend of mine has (and it's on almost 12 hours every day!).

 

A friend of mine has an expensive over-the-range Inverter and it needed a $178 repair after it made a loud bang just after the warranty ended... I had cordless phones that weren't very good either and I still have a VHS-DVD recorder combo with a DTV tuner and I on the rare occasions I want to use it (it's been over a year since I used it), I usually have to press on the reset button and disconnect it as it bugs and it won't even turn off by itself when it happens... 
 
We've got a big Panasonic convection microwave.

There are Four things that make it the best we've ever had

1) Defrosting - Works perfectly evenly, no cooking, no constant turning
2) Auto Menu's - For Rice, Fresh Veg, Potato's, just select the item and when it stops it all perfectly cooked
3) Auto Reheat - Put last nights leftovers in and press go, it tells you when to stir and then stops before it over cooks them.
4) Minimal spattering when reheating - If you set the power to Medium, nothing spatters, it just gradually gets hot, no blast of microwaves to make it spit and then nothing until the next blast.

Under warranty we had the cooling fan for the inverter replaced, but its now 5 years old and not had another issue. It did cost $800 however and is still made in Japan.

Regards

Nathan
 
The inverter PRINCIPLE is sound, lower constant power vs. full power cycled on and off. But in the same time as inverter was invented and implemented, gross cost reduction in ALL appliances was also implemented. So the inverter may work better, but not for the 30+ years my GE/Toshiba has worked.

Besides boiling water for tea, I use the machine mostly on power 3 or 4. Even so, it does cause localized boiling/exploding and I keep things covered to minimize cleanup.
 
Microwave oven still operating with the door open??How this is -a mystery-this SHOULDN'T happen-All microwave ovens made to use in the US have to meet BRH standards-this includes what is called the door interlock monitor circuit.If the oven tries to run with the door open-the monitor circuit is supposed to blow an internal fuse in the oven disabling it right away.The oven then has to be taken apart-bad interlock switch or whatever issue caused to door problem to be repaired and the internal fuse replaced.That is a good reason why so many disfunctional microwaves are thrown out-the door interlock monitor circuit did its job.The average customer doesn't know that.A repairman could fix the machine-probably at low cost-less than a new one.
The invertor system in the Panasonic ovens rectifies the incoming line voltage-then converets it to a higher frequency-the oven magnetron transformer resembles a TV flyback transformer rather than an iron core conventional transformer.The efficiency is better-transformer is smaller and lighter in weight-and the invertor controls the voltage going to the transformer more precisely.There is also thought that the magnetron tube gives better efficiency when run at the higher invertor frequency.HV experimentors salvage the invertor HV unit from old junked Panasoic ovens as a variable HV voltage power supply for HV experiments.But if you use the supply in this manner-its output HV voltage is LETHAL!
 
Inverter supplies

Fascinating thread. I have a 'redundant' inverter supply which I will play with when I have time. (don't panic, Tolivac, I already have a 100KV laboratory supply which also doesn't give second chances!!!). If I read correctly, Hydraulique stated that he had 'bodged' the door interlock (reply #3), so that it had jammed in the 'door closed' position.

All best

Dave T
 
DaveTranter-Interesting how someone else here deals with HV supplies-Deal with them here at work in the transmitters-and the primary voltages that run the transmitters are deadly as well-we take NO chances out here-4160V 3ph primary power,and 5Kv,6Kv,12Kv,15Kv DC power supplies and one at 30KvDC @30A.one of the transmitters here has killed one man and just about another-so were are very careful here-and the RF energy is something to respect-250Kw and 500Kw of SW energy is nothing to laugh at-makes the microwave oven supply a toy-of course a dangerous one.
 
"Microwave oven still operating with the door open??How this is -a mystery-this SHOULDN'T happen"

Rex, we still have the unit, and you are more than welcome to visit and we'll demonstrate. :) When the original latch switch failed the thing ran regardless of whether the door was open or closed, and it does the same thing now that the replacement switch has failed.
 
I use one of three of these Panasonic Inverter based microwaves from time to time. For a low cost standalone oven they have proved quite decent overall. They sure are lightweight though! The Inverter power control is much more sophisticated and well modulated then any of the old Triac control of the old 60Hz transformer HV supplies. They sure outperform the old 1984 Whirlpool I have at work.

About a year ago I repaired the 10+ year old oven that belongs to Annette's parents. That oven is run a LOT, a several hours a week, mostly defrosting and some water heating. The inverter had a failure, I created a thread on the repair in case you want to look under the hood:

http://www.automaticwasher.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?43694

The inverter has gone through a couple design changes and they uprated the fan at one point. The one I repaired is an original design and finding the transistors was tricky as they were at end of life already. I have a friend that manages a ex-Panasonic repair shop and he can attest to the newer inverters being more reliable. I wanted to see if I could make this one run again and so far it is holding up. If it ever fails again I will just buy a new inverter kit for the oven to get the new design and bigger fan.

There is no service information for the inverter as Panasonic doesn't want anyone messing with them. They have a 3500+ volt @ 1/2 amp output so I can understand why they don't want the usual tech messing with them. Luckily there are a few hams out there that have been using the oven inverters as HV power supply for medium power tube RF amplifiers. There is some documentation and reverse engineering on the web from them.
 
DaveTranter . . .

Please re-read my earlier post. I did not "bodge" the door interlock on the oven, in fact I never opened the oven body up or messed with the interlock or any electronics. I would never defeat any safety device on a microwave or advocate that someone do that.

 

What I did was remove the door - easy enough to do without tools as it is designed to be removed for cleaning - and then opened the door assembly up to repair a broken spring perch. As noted, there are no electronics in the door. What is in there is the typical plastic vertical slide that is molded in unit with the two tongs that protrude into the oven body when the door is closed. At the bottom of this slide is a little coil spring much like in a ballpoint pen. It's attached to a tiny little plastic hook molded with the side of the door frame. That hook broke and thus the spring bottom was no longer attached and the the door wouldn't stay closed. All I did was to drill a little hole in the bottom of the door and insert a nylon threaded bolt through that so the top of the bolt was at the same vertical location as the broken hook. I then hooked the spring bottom through a tiny hole I drilled in the bolt and reassembled it. The spring was in exactly the same location as before and nothing else had been damaged.

 

With the spring fix everything worked normally for a couple of years until the incident when I reached in and realized the oven was still running. At that point I had no more interest in that oven - this being the second failure - but wanted to wait until the weekend to find one on sale. For safety I then plugged the oven into a switched spike bar so I could be absolutely sure it was off before opening the door. This worked for another day until the display went wonky and the oven wouldn't work at all, hence my feeling that this was a problem in an IC chip or something as the door interlock shouldn't affect the display. It didn't give an error message, just gibberish.

 

I gave Panasonic a second chance with the second oven, but once that started requiring two or three hard slams of the door to work it just wasn't worth my time to study up on how to safely and correctly open it up and service it.  It went into the trash at 13 months of age and I'm buying no more Panasonic appliances.  Obviously my experience with Panasonic isn't unusual from some of the other posts here.
 
Looks great, but at 20" deep we'd be bonking our heads constantly trying to use it as an OTR.

I've heard commercial microwave ovens are better shielded. True?
 

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