Go7 Black screen

[masterchief217]

I bought a centipede that was converted into a twin cobra. When I bought it I was getting no picture or sound so I replaced the power supply and it worked but the monitor curled at the top a little. I did a cap kit and the mod that the instructions told me to do for the cap kit. double checked all my caps and wires Im getting a slight glow on the neck of the monitor and I hear the monitor turning on but Im getting a black screen. it makes the sound when i insert a coin and it plays the music if I start a game but Im getting a completely black screen. not sure what I should do