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Help Identifing a Part

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Sulaiman

Sun Feb 20 2011, 09:22AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I'm pretty sure that's not a 1200 Amp thyristor so I guess 120A 2000 V.
It's almost certainly Silicon, I've never seen a selenium rectifier in this package. Selenium compounds are often toxic (and have been used as a poison), are less reliable and less efficient than Silicon, in short they have not (to my knowledge) been used in new designs for decades.

Steve Conner

Sun Feb 20 2011, 11:01AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yes, selenium rectifiers are a replace on sight item in old tube equipment, due to their habit of catching fire and stinking the place up with foul-smelling toxic fumes.

I've seen the blue finned ones, they are good for maybe 5 amps? It would have been part of an auxiliary circuit.

dmg

Sun Feb 20 2011, 04:34PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

Steve McConner wrote ...

I've seen the blue finned ones, they are good for maybe 5 amps? It would have been part of an auxiliary circuit.

I wonder if the blue color is some type of color coding? or is it just the material coating itself?
I got this tiny little one right now on hand, but its brown. its quite old and isnt really good for much, but still works at least.

Nah

Mon Feb 21 2011, 04:08PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Steve McConner wrote ...

Yes, selenium rectifiers are a replace on sight item in old tube equipment, due to their habit of catching fire and stinking the place up with foul-smelling toxic fumes.

I've seen the blue finned ones, they are good for maybe 5 amps? It would have been part of an auxiliary circuit.

Now, I have to politely disagree with you. I've worked on many sets with selenium rectifiers, and I've never had to replace one. Then again, after their repair, I put them on the shelf and forget about them. I've heard that you like working on tube amps so in that case, I think your right about replacing them.

I've never heard of a colour coded system?

dmg

Mon Feb 21 2011, 04:19PM

Registered Member #2628 Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627

Me either.. but ive seen them in several colors and I just wondered if it actually meant anything.

Xray

Mon Feb 21 2011, 05:03PM

Registered Member #3429 Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288

Nah wrote ...

I've never heard of a colour coded system?

I can relate to that smell of a burnt selenium rectifier! I'm old enough to have replaced MANY back in the "dark ages" of vacuum tube electronics. As far as color goes, I believe it's just a manufacturer's preference. I've seen seleniums in just about every color of the rainbow. The most common colors in consumer electronic devices were blue and red. In large battery chargers they seemed to always be brown for some reason. But like I said, I really doubt that the color indicates an electrical specification, just a manufacturer's brand ("brand" as in branding a cow).

Xray

Mon Feb 21 2011, 05:04PM

Registered Member #3429 Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288

[quote]
[quote]

EDIT: OOPS! Ignore this post. I screwed up when I tried to edit my previous post. Sorry.

James

Tue Feb 22 2011, 12:29AM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

Nah wrote ...

I've never heard of a colour coded system?

Once you've had one fail, you'll never be content to leave an old one in place. I cannot thing of anything more foul smelling that I've encountered. I replace them any time I find them, often leaving the original in place for appearance and stashing the tiny modern diode down under it. The voltage drop of a silicon diode is much lower so sometimes something else needs adjusting to compensate.

As for the part in question, that's a silicon power diode or SCR for sure. I have several similar parts and used one in the capacitive discharge spot welder I built. 1F 25V capacitor bank and a 120A SCR have been handling the 10kA pulses so far. I built it for welding together battery packs for which is works great.

Patrick

Tue Feb 22 2011, 04:20AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Back to the subject at hand, I'll bet money thats a normal power diode or SCR, or on the outside of the horseraces maybe a TRIAC, but Ive never seen them that big.

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