[R-390] Second R-725 on ebay

[David Wise]

The purpost of the transformer is to separate the
PTO and BFO heaters from the main heater supply.
(The main supply is grounded.)  This allows the
heaters to be floated up to a positive DC
potential, which has a known beneficial
effect in reducing hum.  (It prevents
filament emission.)

Dave Wise

-----Original Message Excerpt-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net] On Behalf Of ToddRoberts2001 at aol.com
Sent: Saturday, May 09, 2009 5:29 AM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Second R-725 on ebay

I see it looks like there is some kind of added transformer next to the  
regular power
transformer on the underside also on the R-725?
 
73 Todd WD4NGG