This is why we make prototypes
I have had a few "blue smoke moments" when testing prototypes. One of the worst was when testing a power supply for endurance at full load. It took hours for the thing to warm up, then "boomf!". I took the lid off, and there was a bit of a crater in the PCB. A few power devices had died. It looked like there had been a short, perhaps due to bad soldering. I thought this because our regular technician was busy at the time, so the production engineer did the soldering. The board was patched, and the dead parts replaced. Switch on, load up, and wait. A few hours later -- "boomf!". OK, this was not bad assembly. Something was overheating. I eventually tracked it down to a device that needed a higher voltage rating, in order to reduce leakage current that caused thermal runaway. I should have known about this, but the data that would have warned me was somewhat buried in the component datasheet. "Every day is a school-day", as my boss said at the time.
This faffing about with repeated lengthy tests delayed the product launch somewhat, but you have to consider what may have happened otherwise. Say we shipped hundreds of PSUs in the winter, and they did not overheat at that time. Come the summer, and they start going "boomf!" all over the country. Multiple callouts at our expense, and all profits wiped out.
Biting the hand that feeds IT
