Hi David, I was a civilian Electrical Engineer with the US Army before the FAA stint. We absolutely required the components used in critical systems to be operated well below the "rated" thresholds. I did HV substation design for places such as Marshall Space Flight Center and Redstone Arsenal - the Army missle development center where the original Redstone rocket was developed to launch the USA's 1st satellite in 1958. I was bombarded by manufacturers wanting us to use the 'latest' electronic versions of the substation protective relaying systems in the 1990's which until then had been totally analog. I refused to allow that then, primarily because they relied on electrolytic capacitors in their 'power supply' & 'transient bypass' systems (internally to the relay). The electrolytic caps were the weak link. A 161Kv substation is no place for components sensitive to transients & guaranteed to fail after 10 yrs or so. Those same caps have destroyed more PC motherboards, HD TV sets, etc. than any other cause. I have a ESR meter which allows one to check PC board caps in circuit - It uses an AC low level voltage which will not cause semiconductors to activate, & which gives ESR values for the caps. We used to try to repair expensive PC boards in the FAA systems rather that "board changing". That way we could keep one good spare & fix the failed one when replaced, keeping it as the spare. Electrolytic Cap's were the main culprits in the failures. Thanks for the reply! 73 Gill
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