Concerning the display chips and the FT301D.? It was perhaps two years after obtaining my 301D in 1977 that my first display chips failed.? I ordered some new replacements and corrected the problem.? I found that if the rig was used day after day the display chips lasted several years.? I noticed when the rig was shut down for an extended period of several months to several years there were always segments out when I repowered the rig.? Then I began to notice that even a few of the brand new chips had defective segments.? This got me wondering; could "whiskering" which was a fairly common problem of the 1970's area be the culprit?? Some materials in chip, pcb, and discrete component production would grow little bitty whiskers that would short and take out delicate electronics.? NASA and others lost a number of satellites due to whiskering problems in space.? The US military loss due to this is still classified.? The little whiskers can be inside components, outside components, around pcb traces and so forth.? Why else would brand new TIL chips that hadn't been in circuit nor had they suffered any heat mysteriously show up with the same kind of segment problems as the ones operating for several years installed in the rig?? Fortunately I have enough spares on hand that I can sort through them to get enough good ones operating correctly.? I picked up a stock of them back in the day "just in case."? :-)? This is open for discussion but I think the problem was a manufacturing defect perhaps the well known whiskering problem and not related to burn out and so forth.? Parts don't burn out that are sitting in storage, but whiskers do grow while in storage and sitting on the shelf.
https://nepp.nasa.gov/whisker/reference/tech_papers/2006-Leidecker-Tin-Whisker-Failures.pdf
