i have a console here with a very similar problem, but even stranger
without going into too many details, i have no video or sound in general, but it does play games and sync controllers. you ask how do i know it play games? well for one, the sound of the disc drive, and for two, well here's the strangest part. i get audio, but only for a brief moment if i change the channel and change it back, then it cuts out. it will do it everytime i flip the channel and go to back to it. i originally figured it was the ANA chip and went to heat gun it as this has worked several times for me in the past. as soon as i started a capacitor shot out of the board off of the ceiling like a rocket. i am very experienced with xboxs and the heat gun, i am very positive i was doing it correctly. but i suppose i will give the x-clamp a whirl and let you know how it goes.
thanks!