[R-390] Selenium Rectifier

[Barry]

Actually, I was looking at one of the physically larger rectifiers (P/N
276-1185, but it's PIV is "only" 50V.  It is larger than needed (25A
capacity), but has solder tabs instead of just leads.

I suppose I'd opt for P/N 276-1181 (200PIV, 6A), though.  It doesn't have
solder tabs, but it is easy enough to solder to the large diameter leads.

Thanks!

Barry - N4BUQ

----- Original Message ----- 
From: "Tim Shoppa" <tshoppa at wmata.com>
To: <r-390 at mailman.qth.net>
Sent: Thursday, November 17, 2005 8:51 AM
Subject: Re: [R-390] Selenium Rectifier


> I figured an amp or two would be a sufficient rating for a replacement
rectifier.

Oh, yeah, definitely.  A 1 Amp selenium stack (even low voltage)
would be physically much larger.  And the 25.2VAC winding in
the transformer is only rated at 1.2A.

I see the smallest Radio Shack bridge rectifier is 1.4A 100PIV.

> K101A and K101B are all that's powered by the rectifier, right?  I'm
> not looking at the schematic, but does anyone know if
> the break-in relay is also powered from this rectifier?

The break-in relay coil is 6.3VAC from the filament winding. The
ground return of the selenium bridge goes through one set of
the break-in relay's contacts, but that's not really "power", just
completing the ground return.

> I don't recall
> seeing it in this line, but it would seem it needs DC from somewhere...

My reading of the schematics is that the break-in relay coil is
AC, not DC.  I never liked AC coil relays but if the alterniative is
a bunch of selenium rectifers...!

Tim.
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