Fender Princeton 112 Plus Help finding a short

I have a fender Princeton 112 Plus amp that someone gave me When I first tried it , it was working but had bad scratching sound from one of the pots. So I cleaned them all with electronic cleaner one of them still was terrible so I replaced it with a good used one I had. I tested it before using it to make sure it was good. Also the power cord was frayed badly so i replaced it also. Then after I did this when I turn it on it pops the fuse. I checked it for any place i may have caused a short but can't find anything visibly wrong. I thought maybe When I put it back together I got one of the wires in the wrong place but I had marked them prior to taking them off so that shouldn't have happened . I just downloaded the service manual and I'm going to check the schematic. I just was wondering if anyone else has ever had a problem like this and knew what it was. It seems like it has to be something I did to cause this and it shouldn't be much to repair it. i appreciate any advice you can give. Thanks