[Chuck Schwark]

The 5X4 and 5U4 are wired differently.  They are NOT pin-to-pin interchangeable.
Just checked Sylvania tube manual on-line.

Chuck

Hi folks,

I am not too versed in Philcos and could use some basic help. I just picked up a very nice 37-670 yesterday and have no plans to power it up until after a full recap/restoration, etc. But just going over the chassis during my initial inspection gave me a bit of worry.
The radio calls for a 5X4 rectifier. The tube in the transformer socket is a 5U4. I know these are wired differently, but since the tube socket is part of the transformer I can't go underneath to see if someone in the past modified the wiring to fit a 5U4 tube. 
Can anyone tell me, off the bat, the right way to determine whether or not the socket's been modified. I know, a basic question but I'd rather ask than go full speed ahead and screw something up
I found already though that a few of the electrolytics have been swapped out and JOY who ever did it paralleled them right into the original electrolytics. Sweet.
Thanks for the help everyone.

Ted
Bristol RI