Old Time Selenium Rectifiers - Can someone explain them?

[Rnktapp]

Can someone tell me a little about selenium rectifiers, how to check them in a circuit, and how to replace them with a diode, and how to know what type of diode?
(Tube radio fan here.)
Thanks,
Richard

 

[Nigel Goodwin]

Can someone tell me a little about selenium rectifiers, how to check them in a circuit, and how to replace them with a diode, and how to know what type of diode?
(Tube radio fan here.)

You simply replace them with a suitable silicon rectifier and a wirewound series resistor (for surge limiting), we always used a BY127 for the diode, I can't remember what value resistors we used to use? (I haven't done one for something like 30 years?).

You check them like you would any rectifer?, measure the AC in and the DC out - the voltage drop across them is too high for simple ohmmeter checks.

 

[bloki]

Selenium rectifiers are allso semiconductor devices but amorphouse. In old days we used to say taht each plate of rectifier can whithstand about 30V of reverse voltage and that each square centimeter of it's surface can whitstand 100mA of current. You should count number of plates connected in series and calculate area of plate. One of the characteristics of selenium rectifier is: they have about 30-50V voltage drop when they are designed for 250V AC.

 

[Klaus]

And another peculiarity about selenium rectifiers is that they require the evacuation of the room if accidentally (or deliberatly :twisted shortened :lol:
Who here is old enough to remember using these things? I'm putting my hand up :wink:.
Klaus

 

[stevez]

I remember them ..... though silicon diodes pretty much had replaced them in new equipment. I remember the local pharmacy in our small town, had a tube tester, as did other stores, and quite the selection of tubes. It was not uncommon for my dad to get some advice from a friend and swap some tubes of the tv didn't work right. Sometimes that worked - if not the repairman was called.

 

[Nigel Goodwin]

And another peculiarity about selenium rectifiers is that they require the evacuation of the room if accidentally (or deliberatly :twisted shortened :lol:
Who here is old enough to remember using these things? I'm putting my hand up :wink:.

Old EHT triplers also used selenium rectifiers, you could go on a call to someones house, walk up the path and smell the stench before you got to the house - turn round and go back to the van to get a new tripler :lol:

A common 'game' was placing the old tripler under the seat in someone elses van :lol:

 

[Rnktapp]

That was a funny story! (Thanks)

I did measure the AC in and the DC out, and the rectifier is still good. It was amusing to read about the old days, and the smell if the rectifier got shorted...
Thanks for a laugh to start my day! :lol:

 

[Nigel Goodwin]

Re: That was a funny story! (Thanks)

I did measure the AC in and the DC out, and the rectifier is still good. It was amusing to read about the old days, and the smell if the rectifier got shorted...
Thanks for a laugh to start my day! :lol:

You won't laugh if it fails! :lol:

They really do smell extremely bad!.

 

[Dean Huster]

And to think that as a kid, I used to deliberately short them just to see the sparks. I think I still have a few of them .... or were those heat sinks I was seeing?

Richard, if you don't know about them, you need to check out the following antique radio forums:

**broken link removed**
**broken link removed**
http://www.vintage-radio.net/cgi-bin/yabb/YaBB.pl

Of course, with the first two, if you scrap everything after the first slash, you have their main site which is full of all sorts of good information.

Dean