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Nostalgia thread, did you work with Selenium rectifiers?

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schmitt trigger

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My first electronic project that worked, a small audio amplifier, I used a scavenged selenium rectifier.

I also repaired a couple of radios that used them.
On one instance, one blew up and the smoke was nasty.
I later learned that these rectifiers were highly poisonous.

Did you ever came across one?
 

dick_freebird

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I found one in an older ('70s) dirt bike as the main (only) rectifier.

Had some in junk boxes which were cool to look at, but not
any more useful than other diodes.
 

betwixt

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Selenium certainly stinks when it burns!

I used them back to around the mid 1960's, both as power rectifiers (remember the square blocks with lots of fins?) and small signal diodes. I probably still have a few lying around in the cobwebs.

Brian.
 

c_mitra

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My first electronic project that worked, a small audio amplifier, I used a scavenged selenium rectifier.
I used a galena point contact rectifier for a crystal headphone radio set. The galena crystal can be broken to expose fresh surface and a sharpened safety pin, mounted on a wooden block with glue, was the other terminal. Since we had only one MW radio station nearby, it needed no power or no tuner (I had a 300pf tuning capacitor and the coil was made by trial and error).

But the rectifier was the most mysterious device in the whole set.

- - - Updated - - -

Selenium is toxic but not highly poisonous. It is needed in trace amounts for both plants and animals. I think the rectifying element is CdSe (but I am not so sure now) and cadmium is far more toxic. H2Se really stinks (but SeO2 is far less offensive).
 

schmitt trigger

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If I remember correctly, they had forward voltage drops of several volts.
But compared to vacuum tubes, which had a voltage drop of tens of volts, they were an improvement.

I would love to have my hands on one, to see what the V-I curve looks like.
 

FvM

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For low voltage, selenium rectifiers have been quite popular in the 60s. I found these devices in a component stack

Selen rectifier.jpg
 

betwixt

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I think the last common usage of them was in HV voltage multipliers in early color TV. Inside the "tripler" there would typically be several capacitors and five 'sticks' about 50mm long. Inside each stick was a stack of selenium discs (~50) and a small spring to keep them under compression.

Brian.
 

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