Another Vacuum tube application soon to go solid state?

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kb0nes

kb0nes

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The LDMOS-FET technology continues to march on. Most radio and many TV transmitters today are being made solid state, and thanks to increases in frequency soon the microwave oven may no longer have a magnetron.

It will likely be a few years as Asian magnetron's are darned inexpensive but there are advantages to going solid state too.

A magnetron is a high power oscillator which simply starts to oscillate when it is energized. The frequency is determined by it's physical construction and really isn't all that stable. When the load in the oven cavity changes the frequency will drift around. Using a solid state power source the frequency is derived by a low power frequency variable oscillator then is amplified up to cooking power levels by these new transistors. Operating frequency is completely stable and can be varied over a relatively wide range.

All common microwave ovens have some form of carousel or stirrer to attempt to break up the standing waves in the cavity which cause hot and cold spots. By using a solid state power source the frequency could be varied at will which will cause the nodes and anti nodes in the cavity to vary. No stirrer needed.

Different foods could potentially benefit from being able to alter the frequency of the heating energy too. Frozen foods may respond better to a different frequency then microwave popcorn for instance.

This link is an interesting look as a number of ways that solid state power could improve microwave cooking.

http://www.electropages.com/2016/12/six-ways-to-improve-microwave-cooking-solid-state-devices/

Will be interesting to see how this technology progresses!

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I'm on board whenever it happens!  I'm easily annoyed by burnt popcorn before all kernels have popped, which is how my Panasonic inverter likes to render it -- on the "Popcorn" setting to add insult to injury.

 

Yes, I own a fabulous space age avocado Penncrest popper and it does a beautiful job, but microwaving is so much faster and provides a disposable container.  Besides, if I'm going to invest that amount of time and trouble, I might as well toast up some blanched almonds.
 
TV transmitters have been solid state for the past 25yrs in the low and high band VHF.Only UHF is still tubed-Klystrons,and Klystrode tubes.Harris made the first solid state TV transmitters in anolog-now digital.The klystron type tubes handle powers for each tube-from 20Kw to 65Kw.And the tube only needs 5w to drive it to full power.The solid state "magnetron" s very interesting-will have to see how this come out and how soon.Maybe those UHF TV transmitters then will be SS.
 
If they have the lifespan

Then, great - the power loss to run a magnetron is easily 30-40%.

BUT - we've all seen the super short lifespans of so many appliances. I'd want a SS microwave oven to last longer than the two years max. we have gotten out of the Panasonic Inverters.

 
 
Keven - I'd surmise that these should have a longer lifespan then a magnetron assuming decent design. Solid state electronics don't wear out so they could last. Of course the life span of a magnetron is pretty impressive too. The bane of any magnetron design is the need for >3Kv high voltage. In the olden days when it was done with a big transformer the HV supply was very reliable, but heavy, inefficient and expensive. The early model Panasonic inverters have proven to be a little fragile, but this was due to the HV instability in the inverter itself. The later models have been better judging from the ones I have worked on.

John - While a resto-mod would be cool it would wreck that classic. That needs to have a fully functioning original RF system to preserve the history.

Rex - Take a look at www.gatesair.com Fully solid state LDMOS UHF TV transmitters are available NOW. Except for the highest frequency/power applications I can't imagine any station buying a tube any longer today.
 
GatesAir has made improvements in their TV transmitter designs-now you can get high power SS UHF.So goodbye to Klystrons and Klystrode tubes.Normally I don't like SS transmitters because they can be more complex than tubed models and have higher parts count-those GateAir mode3ls show promise.Have seen earlier then Harris SS Platinum analog TV transmitter on Ch#8 in Richmond,VA.These newer GatesAir ones are much more advanced.If I were shopping for a transmitter would consider this.SW transmitters are adiffrent matter-they STILL have tubes!
 
Audiophile types often still prefer tubes for audio equipment. And so...I wonder if a solid state microwave will find acceptance in audiophile circles. Or will audiophile types feel magnetron microwaves have warmer, smoother food?

 

LOL

 

Although.. more seriously, one tube amp maker has used the example of microwaves to show that tube technology isn't dead. So much for that example. LOL
 
BUT - we've all seen the super short lifespans of so many appliances. <strong> I'd want a SS microwave oven to last longer than the two years max. we have gotten out of the Panasonic Inverters.</strong>

 

Yes, we have seen how long things last. Or don't last.

 

Being cynical, I personally won't expect a new solid state microwave to last a long time. It might be marketed as potentially longer lasting since there is no longer a magnetron tube, of course, but would companies improve overall quality to match the longer potential life? I doubt it. Not in this era. And being fair to makers of microwaves, there is the problem of getting normal people to pay extra for better build quality. Most people want the cheapest price possible at Walmart or Target. Even I am somewhat like that--although for me it's cynicism that "nothing here will last, so might as well get the cheapest choice!"

 
 
Reliability versus planned obsolescence

One of the greatest advances in computing was the replacement of vacuum tubes with solid-state switching components.

Not only did things speed up, the reliability also went through the roof.

Great!

One of the greatest advances in audio recording came about when sound engineers figured out that those of us with absolute pitch weren't making it up and the manner in which SS clips versus the way tubes clip is relevant to dynamic range...and, in short order SS recordings sounded really good.

 

I don't quite believe that SS components have indefinite lifespans, there's too much evidence about micro-cracks and silicon atoms wandering, to name but two confirmed limitations.

 

What excites me about replacing magnetrons - better frequency control (wouldn't be hard), fewer mechanical components, higher efficiency (again, wouldn't be hard).

 

What worries me: I've had tens of microwaves through the years and never seen a magnetron failure. Every single time one has had to be replaced it was because the SS electronics had failed, usually a logic component. There's no reason to believe the perfectly awful consumer electronics to which we've all become accustomed in household appliances will improve. None.

 

I look at it this way - once we get past the early 1980s, how often do automotive electronics actually fail? Relatively seldom. Safety related, nearly never. But who amongst us can say the same for electronics in heat, steam, wet, high temperature stress home appliances? 
 
I look at it this way - once we get past the early 1980s, how often do automotive electronics actually fail? Relatively seldom. Safety related, nearly never. But who amongst us can say the same for electronics in heat, steam, wet, high temperature stress home appliances?


 

Unfortunately, I think there is more pressure on car companies to engineer the stuff to last better than a microwave. If a car has massive electronics failure at 5 years old, the PR could sink the company. Few people will complacently replace a $20,000+ car that wears out/has really expensive problems prematurely. It's even worse for a car company if it's a safety issue. Even a minor safety issue recall can hit the news heavily.

 

The problem is...there is no real pressure on appliance makers. If there was some huge safety problem, that might be one thing. But when something wears out earlier than it should, most people just shrug and--at most--say "that's the way things are built these days!" And then they go to Target to buy something of similar quality (or lack of).
 


since Reagan killed the middle-class rise up the ladder, people not only like having appliances cost the same, year in, year out - they can't afford to pay more for better quality.



 



<strong>Quite true. </strong>



 



<strong><strong><strong>I know the quandary of can't afford to pay more. It's something I deal with all the time... Which is one reason I like shopping used--it's a way of getting better quality than I can afford with my new dollar. And when I do buy new, and have to buy cheap, I shudder a bit because I know I'm not able to get something lasting.</strong></strong></strong>



 



<strong><strong><strong><strong><strong>I'm probably not alone. I remember my mother's mixer breaking, and we went to the store to replace it. My mother decided on the $13 mixer. Thirteen was a fitting number, not just the price, but also the luck we had in the long run with the mixer. But at the time, it was appealing, because it was the cheapest thing in the store at a time when my mother's finances were not their most robust. My grandmother tried to talk my mother out it, and get something better, but cheapest mixer won the contest that day.</strong></strong></strong></strong></strong>



 



<strong><strong><strong><strong><strong><strong><strong>That mixer was not very good. It worked, after a fashion, but it was not as good as the mixer it replaced. And it lasted less than two years before it started acting up. The previous mixer had lasted 20 years, and had been more heavily used during at least half those years than the new mixer.</strong></strong></strong></strong></strong></strong></strong>



 



<strong><strong><strong><strong><strong><strong><strong><strong><strong>So...it would have been better to spend more than $13 on a mixer... I think even my mother recognized that at the time (she'd used the "lasts longer" partly to justify buying more expensive coffee makers).</strong></strong></strong></strong></strong></strong></strong></strong></strong>



 



<strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong>Although...my grandmother became very cost conscious herself, given the realities of retirement income in modern America. Towards the end of her life, she bought a new mixer only barely better than our $13 wonder. It probably wasn't $13, but I'm betting it was one of the cheapest mixers in the store. </strong></strong></strong></strong></strong></strong></strong></strong></strong></strong></strong>



 



 

 
Not to derail things too much, but I've always found it odd that people are willing to buy a new microwave, it goes bad in a few years, they buy another, it lasts a few more years, they buy another and on and on instead of just picking up a vintage Radarange.

Yes, the new ones are more powerful, but I'm willing to dial in an extra minute or two for a machine that will literally last my lifetime.
 
Two year lifespan?

 

 

I guess I must have gotten a good one built on a Wednesday or something, LOL.

 

I have a Panasonic 1100 watt inverter microwave oven that was new and came with the house I bought 16 years ago.  I've been really lucky **knock on wood** as it gets used daily and the only thing that's happened is the light bulb inside burned out about a year ago. 

 

Kevin

 
 
Kevin, the Panasonic Inverter model I repaired a few years ago is likely the same vintage as yours. That one is still going strong with lots of usage after the inverter repair.

When I finally pull down the KitchenAid convection OTR microwave I have now, I have a hunch that one of those Panasonics will replace it.

No doubt that the old ovens were tanks though, we have a 1984 Whirlpool MW8550XL here at work and you just can't kill it!
 
RadarRange oven-the machine itself Could last awhile but doubt a lifetime.The magnetron tube will not last your lifetime-and will a replacement be available in the future when the tube fails-if not the Radarrange ends up in the dumpster with the others.
 
We have a GE microwave/convection oven from 2004 that works fine to this day. Thing draws a little over 15 amps in microwave mode. I wish it heated more evenly but it has been reliable.
My parents had a 1990 Montgomery Wards convection oven and the circuit board was always failing, I can't begin to think how many times that thing was serviced. My mother loved it and they used the hell out of it though. I think it microwaved pretty evenly too, even despite not having a turntable.
 

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