The type 83 can operate horizontally just fine, but in one plane, which the   
   TV7 socket position does for you. Think filament sag as they heat up. In one   
   direction, they will have more space so as not to touch the anodes.   
      
   Also, the link given  for an 83 solid-state replacement will not work   
   properly. You need to re-create the 15v drop the 83 has. Search for 83   
   replacements using zener diodes. These will work much more like an 83.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)