Thursday, July 02, 2020

Cooking By Short-Wave

     The twelve-year-old microwave oven failed last week.  Tam bought it not too long after she moved in; my dinky 700-Watt zapper with a balky mechanical timer wasn't enough oven to keep her fed.  She got a modern one, 1100 Watts and big enough to warm up a whole ham.*  It worked well for years.

     Last week, the microwave finished failing: the "buttons" on the control panel have been gradually dying for a couple of month.  It's a problem Litton and Amana solved in the 1970s, with non-tactile glass-surface touch controls -- but the solution didn't stick.  Membrane switches are cheaper to produce and less finicky.

     But they do fail.  The "1" and "6" buttons when first, then the whole left half of the number panel and, slowly, all but the rarely-used controls at the top and the "start" and "stop" buttons.  It wasn't much of a problem, really.  On that model, pressing "start" calls up a thirty-second run and additional presses add thirty more seconds, up to a total of five minutes.  If you're mainly using the microwave to bake potatoes and defrost leftovers (the "defrost" button worked until the last), it's not a problem.

     Then the "start" button died.  Punching around, the only one that still worked was "popcorn," a three-minute, 100% power cycle.  That was usable but it was clearly time.  I ordered a new microwave and it showed up yesterday.

     Why didn't I fix the old one?  Membrane switches is why.  It'll be a bespoke layout, conductive material screen-printed and fused onto plastic.  If it peels apart -- not all will -- you can clean them up, even paint new conductive goop over the old pads, but it's a short-term fix.  There's not much to work with there and nothing will hold up as well as the original.  It's a hundred-dollar-or-less consumer good.   The part that does the actual microwaving?  That's all working fine.

     The Amana RR9 chassis I remember fondly from having been a tech in the factory of a subcontractor that built the controllers for them, way back before the not-yet-public Internet snuck off college campuses?  That thing cost as much as a crummy used car.  The limitation was magnetron life, and those were field-replaceable.  The controller interface was simple -- power in, switched power out, and a pair of leads for a temperature probe in the higher-end models, all on a Molex connector.  In a pinch (or, say, a test equipment maintenance shop), you could replace the controller with a toggle switch; add a pushbutton in parallel to pulse the tube to make popcorn.  Sell a family one of those ovens, and they'd have a microwave for thirty years -- if they could afford to buy it in the first place.  Which is possibly why cheaper, overseas-made ovens displaced them from the market.
* This is not to imply that Tam considers a whole ham a proper snack.  My old microwave, though, wouldn't even fit a some dinners.



Cop Car said...

Ah, yes, lamentations over the genesis of our throw-away culture. I am in the process of replacing an old dishwasher, not because I can't remove/replace the drain pump that has failed but because I know the membrane switches are probably not are not far behind and, at my age (82), I don't ever want to have to play around with a broken dishwasher, again. (Nor do I want Hunky Husband to have to worry about one after I'm gone.)

Fortunately, the much-more-often-used microwave, at 20+ years of age, does nothing worse than fail to heat on rare occasion. Re-setting the (membrane switch) controls, so far, makes the microwave remember why it exists.

Blackwing1 said...

Just a quick typo-check...I think maybe you meant "eleven-hundred Watts" rather than "a hundred Watts".

rickn8or said...

One of my biggest regrets is replacing a 30-ish year-old washer that did what I told it with a newer, more-fragile-ey made one that does what it wants and "I'll unlock the lid when I think it's proper or 60 seconds after the last rotation on the spin cycle."

And the only reason I replaced the old one was because the tub had rusted through a weld seam at the top and would occasionally wet down the floor.

Artaxus Blackriver said...

My family bought one of the first Amana RadarRange microwave ovens back in the 70's.
Twist-dial timer, and mechanical buttons. It was HUGE. 2.5 cubic feet, easily.
Back then, they didn't know how powerful the thing needed to be, so there was no wattage listing. Had it tested in 2000 (yes, it still worked!) when I had to have a door hinge repaired. 1800 watts!

I gave it away at a charity event in 2005 to a needy family. It still worked perfectly!
For all I know, that thing is still buzzin' along, making food hot.

Maybe I should have kept it; I don't think that monster will ever die...

Gewehr98 said...

I miss my old commercial stainless steel Amana Radarange! It got handed down to somebody starting a new home, I'll bet it is still running to this day...

New Jovian Thunderbolt said...

I am sorry for you loss.

Jay said...

My dad bought a 1st generation Amana from a friend who sold restaurant appliances and had used it as a demo, THEN in his house for 3 years after he got a 3rd generation for demo and put the gen2 in his house. $1k USED in ~1980. I got it when I got married. Donated it to the commuter lounge at my university when theirs died (I was 30 and working on my Masters - this was in 1994). It was still in the commuter lounge when my oldest went to the same school - in 2001!

And yes, it was about 2000 watts with just a mechanical timer and a door lock/on-off switch.