[MrFixr55]

The "Diode" mod that I describe is useful for radios that use the 80, 5Y3, 6Y4, 5Z3, 5U4 etc. full wave rectifiers, where the filament is the cathode.  if the filament opens from overheating, etc. or in the old 80s, just from age, and touches the plate, the tube is shorted from plate to cathode.  this puts AC across the electrolytic filter caps, shorting and possibly blowing them up.  In addition, for 1/2 cycle, there will be a dead short across the transformer secondary.  Since these sets usually are not fused, the secondary will burn out, sometimes with fire.  This actually happened to me and I lost an early post-war Philco console, my parents and sister lost hair and I was forced to put the radio to the curb.  Mom would not let me restore it and Dad knew where his bread was buttered. 

The actual procedure is pretty easy.  You can use 1N4007 (1A, 1000PIV) diodes.  I use 3A 1000PRV diodes.  Simply:
-Unsolder the 2 HV "legs" from the Plate pins of the 80, 5Y3, etc.
-Solder the cathode (band) end of a diode to each plate pin of the rectifier socket.
-Slip a piece of heat shrink tubing over each of the 2 transformer HV secondary lead, as far down the lead as possible.
-Solder each of the 2 HV leads to the anode of each of the 2 diode installed.
-Slide the heat shrink tubing over the diodes, covering all exposed leads and the solder "joint between each diode and the
  transformer secondary lead.  Shrink the tubing.
-Add a fuse to the transformer primary between the power cord and power switch.

See the next post for a Scematic showing the "Mod".