don't assume that the wiring to the monitor is still good. it is just one thin wire that is giving a signal too your monitor on a connector you have been moving. without the game booting up it should be dumping garbage to your screen like this one of a board I was working on that has its other problems. this is before I send the reset signal manually on my test set up. this is why I think your game had maybe a bburned out ram chip to begin with and all the fiddling around has broken down your wiring to the connectors on the board. I am not sure if you are testing the voltages on the main board itself or are just checking the output off the power supply. the board booting is not required to get a signal that is why some of the test are to remove the rom chips and see if you get the lines