The AM Forum

Peter Cooper Hewitt (May 5, 1861 – August 25, 1921) was an American electrical engineer and inventor, who invented the first mercury-vapor lamp in 1901 and mercury rectifier in 1902.

https://en.wikipedia.org/wiki/Peter_Cooper_Hewitt

I'm surprised there wasn't a Google Doodle about him today.

While a brilliant engineer, it reads that his family relations were real headline makers.

Wow. :o

73DG

Peter's daughter, Anna Cooper Hewitt:

https://www.grandcentralpublishing.com/titles/audrey-clare-farley/the-unfit-heiress/9781538753347/
https://youtu.be/lDRPPEoz11s

Very interesting.

Jim
Wd5JKO

Happy Birthday to the inventor of the mercury lamp and rectifier!

The Mercury rectifier is 121 years old on May 5th!

I'll only be 70 on the 11th.

Makes me feel absolutely young! 8)

And yet not so young that you fail to appreciate the warm glow of the 866 or 872!  Especially when they twinkle with modulation.  The world's earliest (monochrome) color organ!

Thanks, OM.

MV's forever, tougher than Silicon!

Therefore this arrangement - the best solution already built and working. Got some real PIV there along with the pulsating blue&UV glowz.

Holiday declared in honor of Peter Cooper Hewitt!

Because it falls on a Sunday this year, everyone will have Monday off to celebrate the appropriate lighting devices, rectifiers, and the glowing, ionized Mercury therein.

Happy Birthday Peter Cooper Hewitt!
Monday, May 5, 2025!

Thanks for the many decades of power, unlimited power!* accompanied by a pretty blue & UV glow!

The Mercury Arc Rectifier is 123 years old!

Invented in 1902 by Peter Cooper Hewitt, mercury-arc rectifiers were used to provide power for industrial motors, electric railways, streetcars, and electric locomotives, as well as for radio transmitters and for high-voltage direct current (HVDC) power transmission.

Mercury rectifiers were the primary method of high power rectification before the advent of  semiconductor rectifiers, such as diodes, thyristors and gate turn-off thyristors (GTOs).

Silicon rectifiers and stacks with similar ratings were mass-produced by the early 1960s and have almost completely replaced mercury-arc rectifiers thanks to their lower cost, maintenance, and environmental risk, and higher reliability.

Unfortunately, these modern replacements deprive the devotee of the benefit of staring into a relaxing cloud of glowing, ionized, metal.

* https://www.youtube.com/watch?v=Sg14jNbBb-8

Ok, i will bite! how did Mercury rectifiers fail and what did that look like? by the late seventies when I started working in broadcasting they were already extinct and replaced by solid state replacements. Seen my share of massive diode stacks and the like but never used a mercury tube although back when I was running a old RCA MX on 160 did think about removing the replacements and stuffing 866 tubes in there.

I'd sure like to see what others have to say on how they go and what they have seen!

The mercury vapor rectifiers I've had fail seemed well-used, and the filament oxide? was bad or flaking off and at some point they would flash over or arc inside the tube, conducting both ways. This should blow the fuses on the equipment.

Reasons could also be possibly because they were not fully warmed up, or because the inside had been contaminated, or because of a gross overload/short on the supply output. I've never had one go quietly. Always flash-overs/arcing.

The topic below shows a melted relay that was on the primary of the plate transformer when a 673 MV rectifier arced over as the plate voltage was turned on without soft start. This happened the first time I was testing the transmitter power supply with the new relays in 2009. There was no hint of an impending problem. The breakers across the fuse holders were 30 or 40A and the breakers didn't trip right away, really too big but that was my fault. The arcing inside the tube lit up the inside of the transmitter cabinet. It was pretty cool!

https://amfone.net/Amforum/index.php?topic=18335.msg127928#msg127928

The arc was blue-ish or a little green in it. Once the tube is removed and looked at, there may be nothing to really show that something happened, but a close look may reveal discoloration, stains inside the glass and loose particles. Or may not!

I learned to look carefully at the rectifiers, look for those tiny little particles, usually grey, or sometimes mixed in the mercury to give what looks like 'dirty mercury globs' loose in the envelope. Those would be stuff that came off the filament or electrodes. The tube might be usable, maybe for a short time, maybe at low voltage/current, or maybe will arc over at once. I won't try to use those tubes, though eventually they willneed to be tested and put up for keeping ot disposed of.