I speculated the 5U4 is because of the p.p. output demand. Rob K5UJ On Sun, May 25, 2014 at 1:03 PM, rbethman <rbethman at comcast.net> wrote: > I have the manuals for the NC-183,, NC-183D(a), and NC-183D(b). > > Every single one has the 5U4G for its rectifier. > > Bob - N0DGN >