Jack;
This website has the schematic you need. Go to the home page and scroll down to Schematics. Click on it and scroll down to "100S".
If your amp is blowing fuses and motorboating, try replacing the can filter cap. Old filter caps cause most motorboating and if your amp has the original cap then it's time to replace it!
These caps are available from Antique Electronic Supply in Tempe AZ (
www.tubes andmore.com). Get the 4 section, 40-20-20-20uf, 525 volt cap (the 40-40-20-20uf cap will work fine too). They cost about $32. While you are in there, replace the two 50uf, 75 volt caps in the negative bias supply. If you don't know how to install, take it to your amp tech. Filter caps contain LETHAL voltages so don't mess with it if you are not trained.
Good Luck!
Ryan