Another Vacuum tube application soon to go solid state?

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Turntables vs. wave strirrers

That's probably not quite the right word for them, but there are two systems for distributing the radiation more evenly.

You know, while technically correct, 'radiation' just isn't working for me. It always leads to 'ionizing' vs. 'non-ionizing' discussions.

Let's say energy.

Turntables have many advantages - they can result in food being really evenly cooked. They have two disadvantages - the closer you get to center, the less well they work, not working at all in the center. Their second disadvantage is that the are by their very nature limited to a smaller size of container than the cavity can hold.

Wave stirrers, done well, let the entire cavity be used and distribute the energy evenly throughout.

Those ancient Montgomery Ward/JC Penny and Sears ovens had wave stirrers and cooked really evenly. I remember them.

 

I don't think anyone expects a magnetron to last indefinitely, but at this point in my life, my anecdotal experience with kitchen electronics versus automotive tells me the things are built to fail.

 
 
My complaints regarding the GE not heating evenly, it always heats the top of things up but not the bottom or sides. No matter if I put it on the edge of the turntable or in the center. Even warming up water it does this.

The wave stirrer makes sense why the old Montgomery Ward worked so well, and without a turntable. My grandma had a small one with a turntable and that heated evenly too, about the same age.

If I was gonna replace the GE right now I would only replace it for something that cooks evenly. Does such a thing even exist in modern microwaves?

P.S.
Hmm, perhaps like the trusty commercial Bunn, one could turn to a commercial microwave?

 
If you don't mind

The short lifespan, Panasonic inverters cook very evenly. The inverter function doesn't work any better than the timed systems, it's just a gimmick, but the high power and the even cooking are the real deal.
 
"[...] The inverter function doesn't work any better than the timed systems, [...]"

Well, that depends a lot on what you need. The Inverter is not actually a continuous power range like you'd get from say, a rheostat, it seems to produce around 3 "bands" of power, and then it chops like the timed system does. It seems to me, for example, that 10% is achieved by a band that produces 30% power and it's then modulated by chopping it.

The results might be identical for some things (defrosting, for example), but make a big difference for others. I've shown many people how to make bread dough rise in the microwave by using 10% power in intervals of nuke/rest, and you can make the dough double in size in about 10-15 minutes this way with the Inverter, but it seems to fail a lot in other nukers -- some you can fix by putting a cup of water alongside the dough, some you can't.

Then again, not everybody wants to bother doing that and prefer to wait the hour or two it takes to rise naturally.
 
Microwave ovens even back to the earliest units always had a wave stirrer to aid cooking uniformity. The wavelength of a common microwave is about 4-3/4" so there will be a number of nodes and anti-nodes across the cavity hampering uniform cooking. The stirrer helps by adding random reflections to try to even things out.

The pity was that the turntable came and basically replaced the stirrer. Since the turntable was a sales "feature" it was quickly adopted in every model, people wouldn't buy one without a turntable... The manufacturers were quick to junk the stirrer when the turntable was added to keep costs down. The stirrer probably also reduced the cavity volume slightly, another thing that became a sales feature.

I had an old Whirlpool microwave years ago that I used one of those Nordicware Micro-Go-Round turntables in. The combination of the stirrer and rotating food cooked far more uniformly then today's turntable only ovens.
 
Yes! Phil, that's right

A good wave stirrer and movement mechanism - some now go side to side - produces very even results.

We won't get better ones until we have solid-state emitters capable of staying on frequency - then we can do several different time and frequency and phase variations, eliminating the need for much of the ultra-high voltage and energy losses we now face.

Given my background in IT, I'm the last person to hold onto a technology which can be replaced with a better one. I just have my doubts that the manufacturers will make any attempt to produce products built to last. The earliest consumer microwave ovens still work after 50+ years because they were too expensive not to be 1)built to last and 2)not be fixed when they failed.
 
Interesting to know that some microwaves still have both stirrers and turntables. Apparently I'm looking at low cost ovens that are pinching pennies.

I never put any merit into the idea that things are intentionally made to fail. I consider that a form of paranoia. BUT, due to the fact that nobody will pay money for reliability anymore, many modern items are far less well made due to cost concerns. Therefore lots of modern stuff has a shorter lifespan, but I am not convinced it is intentional.

The second thing I seem to notice is how much better technology is often made initially. When a technology is new there tends to be a lot over design and safety margin built in. Then as time proves out the design is simplified largely for cost cutting measures. I'd wager that the early solid state RF power microwaves will have some of this dynamic in play. Time will tell but I find it all interesting.
 
Tolivac,

Actually, the way these tubes are run in the Amana's, they only way you're going to kill them is with lots of MW popcorn. There are really three generations of magnetrons used in the entire production run. RR 1/2/3H use the old fashioned electromagnet variety (really a military grade tube). There are lots of RR-2 owners in the club, some used as daily drivers (myself included). The mag won't be the weak point if these ever go.

Starting with the RR-4 you have a more conventional PM design. I've sold a few replacements of this tube, but I suspect this might have more to do with the rise in popularity of the RR and the price drop around '74. These machines are everywhere.

If you really want a life-long Radarange, go for a model 8A/9TA/10 or newer. These would be in the '77/78 timeframe, have the revised cooling design that doesn't rely on a couple foam strips, and uses the same Hitachi mag that's still in use today and can be bought brand new. Not bad for a machine that's 40 years old.
 
Phil

Your mention of the Micro Go Round just jogged my memory. My grandmas little Montgomery Ward microwave didn't have a turntable it had one of those but it was broken and she just kept it in there anyway. So it must've had a wave stirrer, I know it cooked evenly albeit slower than ours at home.
 
There is no way I will have faith in an older RR oven that is 40yrs old+The tube is bound to go sooner or later.And---can you still get replacements-often when the magnetron goes-other items can go with it.I can remember the electromagnetic magnetrons-same idea as the old electromagnetic speakers.I used to have a service manual on microwaves-lent it out-never saw it again-was an exclllent book!from Tab Publications.They printed all types of service manuals on various devices.
 
BRIEF Topic Hijack!

"Absolute pitch" - I'd love to experience that just to know what it's like. It's a brain thing, not an ear thing. I've seen people with almost no usable hearing rip their hearing aids out and/or run out of a room because someone is singing (VERY loudly, obviously) off-key, flat, etc. What's funny is that they can't fathom how people with normal hearing are able to stand it.

"Of course there's another aspect to this - since Reagan killed the middle-class rise up the ladder, [people] can't afford to pay more for better quality."

Thank you! Thank you! Thank you! It's a major pet peeve of mine to hear consumer behavior (or any behavior, really) framed as though preferences, desires, etc. are the only relevant factors.... as if the majority of consumers aren't forced to work within parameters they do not set and cannot change.

I now return you to your regularly scheduled forum discussion:-)

Jim
 
Two aspects of hearing don't fade with age/old magnetron

Transient response and perfect (absolute) pitch.

 

Jim, you're welcome to my perfect pitch. It's a curse, a congenital disease and a major source of nausea and headaches.

 

It's why I defend Andrea Bocelli when my non-dilettante music loving friends decry my 'taste' in singers. It's why I was forced to play the violin as a child/teen/student even though I'm horrid at at. Can you imagine the agony of playing in an orchestra filled by people who can't discriminate pitch closer than an octave who are playing fretless instruments?

 

The stupid discussions about how it's all cultural and tempered scales 'prove' blah, blah, blah.

 

Pass. Totally, completely, pass. If only I could. In my next life, no freckles, skin and hair colour besides pink and orange and normal hearing. 

 

As to the lifespan of vacuum tubes - it's all over the place. Just like transistors - we now know that silicium atoms wander out of of place (a lot like Teflon creep or aluminium flow, though the process is, of course, totally different) and that's that for a lot of solid state devices which we once believed were going to last indefinitely.

 

I'd expect a 40 year old magnetron to be coming to the end of it's life, too - but I know a few real Amana RR that are still running perfectly well from that long ago, so - who knows? The transformer, capacitor, diode and tube are all still available so, worst case, it's all repairable.

 

For that matter, there's youtube clips on repairing the most typical Panasonic Inverter failures on all three generations, and all the repairs are pretty easy. It's mainly (shocking, I know) discreet components which go. So, maybe I'll think about one again. I sure do miss the 1350 Watts....
 
Tolivac, you might have missed it in my response, but yes, you can still get the '78 and up magnetron brand-new from just about any source- amazon, ebay shops, your local dealer through a WP #, there's millions of them. The only other parts in the power supply on these are a combo filament/power xformer, diode and cap. Diode and cap are also readily available and the xformer has overcurrent protection to fail safe. You've also got two thermal cutouts on these models, and those parts are available, too. Door springs and glass trays are the biggest weakness, and they're easy to replace.

Should anyone have an old RR they'd like to keep running for the next 50 years, do a google search and I'll pop up. At any given time I've got 50+ Radaranges here, some in the collection, some as parts machines and some under repair for others. I also do board-level work on panels for '76-'84 models. As long as I'm around, there'll be parts.
 
Speaking of microwaves, talking about repairs jogged my memory.  I'd guess it was mid 70's we bought a Litton microwave - huge thing just barely fir in the 18" between the counter top and the upper cupboards, had to be 26-28" wide.  Had a basic touch panel, nothing special.  Worked for years.  then the panel died.  I was adventurous so I bought the latest model control panel - it was the same dimensions, and replaced the old controller with the then high tech model with lots of extra options.  The guts of the machine were the same, but we did gain some functionality. Lasted a number of years after that to be replaced in the late 80's with an OTR GE unit that survived another 15 years.
 

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