I did an AV mod on a Sears light-sixer. I've done this mod many times on a 4-switch Vader, a couple of Jrs., a heavy sixer, and at least three 7800s....but this is a rare occurrence of a mod not working.
I get no video, but when I turn the console on with a cartridge in it, I get to short buzzes in the key of B-flat (50hz??), almost indicating that it's some kind of POST that didn't go well.
The console worked fine before I modded it.
I'm attaching pictures of my external solder points; I'm not concerned about the leads to the audio/video jacks...but if anybody can give me any pointers, that'd be great. It was this mod: