I have an old NMV PTP amp that is a Marshall Bass clone. I wanted to add a PPI master volume and read good reviews on this Rich Mod: http://home.houston.rr.com/texast/images/rich_mod.pdf Found the place where to put the pots (between the caps and 220k resisteors), lifted the caps legs and wired the pots. the issue is that the 220k resistors in the schematic are connected to each other on a common point, but as can be seen in the picture bellow, in my amp they don't connect. a friend told me that since my amp has seperate trim pots for each tube is the reason for this. I asked him where to connect the third lug of the pots, and he said to wire them to ground since "that's how his Master is wired in his Fender". I did that, the amp sounded like it just got a cold or something... and next thing I saw was my power tubes starting to glow I knew that wasn't good, and shortly after that the mains fuse went belly up Replaced the fuse and the amp is fine :angel I still want to make this mod to work, so any one has an idea where the third lug should connect? Cheers.