pvm 20n6u showing only blue on screen

[rx7turbo233]

hi i have a sony pvm 20n6u that only shows blue i made my own cable and it works with all my other pvm no problem ould like to know if i should follow the input to the light guns or do you think its a light gun issue or a cap their is a cap on the neck boad that reads 2.2 uf but when i esr test it it says 470uf and 2.5 ohm esr
i know its bad but im trying to fiquire if that would cause a color issue

if anyone has ever had that issue i would like to know thanks

[mvsfan]

check to see if the cable is wired right, again.

I have a 20n6u and it works great. but if i unplugged red and green, it will only show blue.

sounds like they are not connected right.