Re: Selenium Rectifier / Metal Rectifier queries

copper oxide rectifiers don't deteriorate and can withstand an indefinite short circuit - but in exchange for that ruggedness they have a very high forward voltage drop which rises as they heat up - I tried them once and discovered that they are very much not a precision piece of equipment

Metal rectifiers are still used in things like elevators and radio transmission facilities, I believe. I think they're selenium. There's also the mercury arc rectifier -- although that's not a solid state device. :)

I've heard that copper oxide diodes were superior in that they didn't decay with age like their selenium counterparts (as those of us working old radio receivers know).

Stephanie Weil KC2TJB Holbrook, NY