I've learned that my old spring reverb (Fisher K-10 Spacexpander - this is about 40 years old) has a selenium (unless it has been replaced at some point in its life, I haven't opened it up to look, it had what seemed to be the original valves when I got it so I presume maybe not) rectifier - should I be worried?
I only have the unit plugged in for one or two hours at a time occasionally.
Is there any health risk?

Selenium

I think you will be ok as long as you don't eat it all in one go!

If you want me I will be licking the lead off these pipes!

Mart

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http://www.myspace.com/cottonsalamander

There is no inherent health risk, assuming you don't spend you time chewing on the hardware! And no particular need to worry. Selenium rectifiers are still made and used in a range of specialist applications where silicon recitifers can't do the same job, and selenium is also used in various photo-electric devices.

However, if you were planning to have the unit refurbished or repaired at some point, then it would make sense to replace the selenium rectifier with modern silicon diode(s) at that time. With things like vintage radios and TV, restorers often disconnect the selenium rectifier but leave it in situ to maintain the vintage look of the hardware (if it is visible).

If a selenium rectifier starts to fail in use, it normally overheats and produces a really nasty garlic/onion sulphurous kind of smell that can't be ignored. The fumes are really noxious but not life-threateningly toxic or carcinogenic in likely concentrations in a room -- but you won't want to stay anywhere near the faulty gear anyway! Just switch it off and take it outside (while holding your breath!). Come back in a week after the smell has gone to collect it for repair.

It is usually fairly simple to replace selenium rectifiers with modern silicon diodes given some electronics aptitude and a voltmeter, and you can find information on how to work out what specification the selenium rectifier has on various websites.

Hugh

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Technical Editor, Sound On Sound

Thanks, I'll pass that on to the forum where concerns were raised that prompted my question.

it's good for Dandruff though !

Quote Neil C:

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Thanks, I'll pass that on to the forum where concerns were raised that prompted my question.

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Oi! The information given here is for the exclusive benefit of SOS forum users. Not the rest of the world...

hugh

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Technical Editor, Sound On Sound

Mmmm. Dead rectifier. Once sniffed, never forgotten

When replacing these with silicon rectifiers in 1 valve record players we also used to add a resistor in series (about 100ohm I think), to make life a little less stressful for the reservoir cap.

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It wasn't me!
(Well, actually, it probably was)

Can't be that poisonous...

Selenium in the equipment, asbestos in the walls, cholesterol, salt and sugar in the food, stress when the red light goes on - we're all doomed.

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No longer a forum member.

Yes it certainly stinks!
They use to punch thru' in early TV's and since they were quite big the smell used hang about for days.

Probably no matter in low voltage equipment but if replaced with silicon in HV kit use a stopper resistor to keep the HT about the same otherwise you can have a fizzing electrolytic to go with the stinking rect!

Dave.