Selenium rectifiers

[Findm-Keepm]

Originally Posted by Electronic M

Option B would be to take 7 modern diodes and string them in series as 7*0.7 = 4.9 which should be close enough to 5 to not matter much, and possibly cheaper than a dropping resistor.

He's got two selenium rectifiers in a voltage doubler configuration - best not to use series diodes in his application but they are fine in a straight half-wave configuration.

Of note, I had fun experimenting with an old GE Selenium today - put 40V from one of my Lambda supplies on the anode, and hung a 120 ohm 10 watt resistor off the cathode to ground - got 353 mA through the selenium, and had a volt and a half of loss through the selenium. My guess is they get leaky, and drop less across them as they age. I've got a coffee can full of Sarkes (ST logo) seleniums in the shop at home, and will try one or two later tonight. I think my Sorensen DCR40-40 is up to the task - just gotta get the right load without exceeding the limits of the selenium rectifier, as my shop at home is quite small and I don't want/need a stinkfest again. I had a Silvertone portable give up it's flyback in there last May, and it still smells of burnt flyback.

Cheers,