[Boatanchors] 5U4 - 5Y3

[Mark]

Did you check the instruction manual on the NC-183D?  I don't recall 
many receivers using a 5U4.  The NC receivers I have owned all use the 
5Y3 and I seem to remember my 183 also had a 5Y3.  I wouldn't want to 
subject the transformer to that extra amp of filament draw. The plate 
side wouldn't matter since not many receivers draw 150 ma of current.  
Many of that era could also use batteries via a plug on the rear panel.
73,
Mark, W4FJE