Old selenium rectifiers - UK Vintage Radio Repair and Restoration Discussion Forum

newlite4 · 11th Feb 2019, 12:23 pm

I have a quantity of old selenium rectifiers. Is there a way of testing them to see if they are worth keeping or should they be assumed too old to use and be disposed of. They may be good to "fill a hole" to maintain originality using a silicon by-pass, but better to be actually used if possible.
Neil

The Philpott · 11th Feb 2019, 12:39 pm

As an example i bought an elderly battery charger with 12v/6v/2v tappings, and a big green painted selenium rectifier. We 'scoped the output and it was a perfect full wave rectified trace, such that it was put straight into service. I think that very many of them will be ok. If they look uncorroded suggest energising them, and using a 'scope. If they start to smell switch off and ventilate the room!

Dave

Nuvistor · 11th Feb 2019, 12:54 pm

I thought battery chargers used copper oxide rectifiers due to being more suitable for low voltage high current. Probably replaced by silicon now.

paulsherwin · 11th Feb 2019, 12:55 pm

I don't think it's worth trying to use them in anger, though as you say they might have a cosmetic use.

barrymagrec · 11th Feb 2019, 12:57 pm

The big old ones with fins may be copper oxide, not selenium - and basically, if they work under load fair enough. Not so keen on the small contact cooled types though - they`ll certainly fail sometime soon.

11th Feb 2019, 12:23 pm	#1
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	Old selenium rectifiers I have a quantity of old selenium rectifiers. Is there a way of testing them to see if they are worth keeping or should they be assumed too old to use and be disposed of. They may be good to "fill a hole" to maintain originality using a silicon by-pass, but better to be actually used if possible. Neil __________________ preserving the recent past, for the distant future.

11th Feb 2019, 12:39 pm	#2
The Philpott Dekatron Join Date: Aug 2016 Location: Colchester, Essex, UK. Posts: 4,106	Re: Old selenium rectifiers As an example i bought an elderly battery charger with 12v/6v/2v tappings, and a big green painted selenium rectifier. We 'scoped the output and it was a perfect full wave rectified trace, such that it was put straight into service. I think that very many of them will be ok. If they look uncorroded suggest energising them, and using a 'scope. If they start to smell switch off and ventilate the room! Dave

11th Feb 2019, 12:54 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Old selenium rectifiers I thought battery chargers used copper oxide rectifiers due to being more suitable for low voltage high current. Probably replaced by silicon now. __________________ Frank

11th Feb 2019, 12:55 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,936	Re: Old selenium rectifiers I don't think it's worth trying to use them in anger, though as you say they might have a cosmetic use.

11th Feb 2019, 12:57 pm	#5
barrymagrec Octode Join Date: Dec 2017 Location: Morden, Surrey, UK. Posts: 1,557	Re: Old selenium rectifiers The big old ones with fins may be copper oxide, not selenium - and basically, if they work under load fair enough. Not so keen on the small contact cooled types though - they`ll certainly fail sometime soon.