This is an article series whose purpose is to shine a comprehensive light on one important aspect of technology that only gets passing mention: Our ability to determine how long a component or system can function based on the engineering decisions made in the interests of monetary consideration and/or reliability. This is especially germane today, as decisions about discarding a technology item at “end of life” now impinge on how much toxic waste we are loading the environment with. ( I have yet to find an “obsolete” cellphone or computer that didn’t work perfectly when discarded, for other than mechanical or liquid immersion damage. ) The definition of obsolete depends on who you ask. The new smartphone you buy today is only a few percent actual new technology compared to the old smartphone your are discarding.
So we seem to have uncovered the operating model that most companies producing and selling technology have adopted:
The model for tech from approximately the 1920’s to today involves having key components in your product which have a known MTBF ( mean time before failure ). Thus you can predict a known replacement rate for your product. Start a second product stream offering replacement parts for the ones you know are going to predictably fail.
Unless or until the majority of your users are technically savvy enough to realize this is a way to keep selling products in a saturated market, one is assured of continuing and predictable sales and profit
We start with old technology.
One could argue that vacuum tubes were inherently unreliable, so they made them as robust as possible and just accepted their limitations. This turns out to be a bit wide of the truth.
In a step-wise fashion, the manufacturing process evolution for the vacuum tube went something like this:
- The first vacuum tubes were handmade with limited production.
- As soon as production ramped up to feed demand, it was inevitable that the manufacturer would tweek the processes used to make a vacuum tube to minimize the amount of time it takes to assemble the finished product from raw materials, to ready to assemble, and assemble (using hands, jigs, and other production equipment).
- As soon as all of relevant costs have been driven out of the system of producing vacuum tubes, the manufacturer rightly looks to other means to make a profit. (Process tweaks and labor input reductions) Sooner or later the ecology of manufacturers who produce vacuum tubes reaches an equilibrium which, despite their best efforts, doesn’t allow any greater profitability.
- Product lifetime now looms large. Sell more product over time, make more profit.
( Note: this describes the manufacturing process evolution for most “tech” products. )
Ways To Sell More Vacuum Tubes
- I only learned about this particular lifetime determinant recently. It seems that in order to get the filament temperature high enough for electron emission, the tungsten had to be alloyed with thorium, which raises the melting point to that of a tungsten/thorium alloy (well above the temperature where the alloy emits electrons. The amount of alloying is directly proportional to the time a DC current-over-time applied in a plating tank. The tube life is directly proportional to the time it takes for the thorium to boil off. More thorium – More lifetime. As the final boil-off occurs, the filament temperature is rises above the melting point of tungsten which results in the filament overheating and burning out. Vacuum tubes manufactured for the US Military were larded up with thorium, and thus met the extended lifetime specifications the US military demanded.
- A getter is a deposit of reactive material that is placed inside a vacuum system, for the purpose of completing and maintaining the vacuum. ( https://en.wikipedia.org/wiki/Getter ) The quality and amounts of various elements is adjustable by the manufacturer and will determine vacuum tube life. I addition, you can get a short lifetime tube just by eliminating the getter. (We have plenty of examples without getters)
- In order assure that parts were available as they wore out “normally”, the tube manufacturers put a tube tester (stocked with replacement tubes ) in every convenient location throughout a geographic area. (Drug and hardware stores typically)
- Make and sell more end products using the same (or slightly improved) technology. This is accomplished by the “Longer, Lower, Wider” paradigm used by the auto industry (and now applied to radios, televisions, etc)starting around the 1940’s. This involves making a greater variety of the same (or slightly modified) product in a different package year to year. Anyone who has read those old ads can see this methodology in action.
Some of the environmental results of the vacuum tube era were:
- Mounds of glass along with refined metals (tungsten, thorium, steel, and others) and minerals (mica) added to landfills. It is unclear if any of the glass was recycled.
- Some of the metals and minerals were leached into the ground by rain.
- Large amounts of scrap-metal ( chassis ) and wood ( cabinets ) ended up in landfill and were either recycled or rotted into the ground.