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Why did repeated heating and cooling cause vacuum tubes to fail?
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vacuum technology
Diagram of a McLeod gauge.
In the context of vacuum technology, repeated heating and cooling cycles cause vacuum tubes to fail due to thermal fatigue.1
When equipment is switched on and off, the internal components of the tube undergo constant expansion and contraction. Over time, this process leads to physical fractures within the tube's interior structure, ultimately resulting in device failure.1
Beyond thermal fatigue, vacuum tubes also fail due to the degradation of the cathode caused by residual gases present within the tube. These inherent limitations, along with the time required for tubes to "warm up," were key factors that motivated the development of the transistor as a more reliable, solid-state alternative.1