LOL...
back on topic, so, you fixed the RROD, doing the clamp mod, now you only have high def video. it could be internal, but I would start with the AV cable. you know there is a switch on the cable near the base, when in HDTV mode the yellow is not active, if the system is on and you just flip the xbox sometimes freeksout and needs to be restarted. try that, turn it off, put it in normal mode, plug it in and turn it on. see what you get. if it still dont work, try and borrow a av cable, or buy one used at Game stop.
you could check internally at the back AV chip near the terminal to see if something looks off, but it is hard to diagnose.
either way it is functioning for its last few months of life, enjoy as long as you can, put those washers and bolts back in. it is working becouse you added pressure to the CPU and GPU and reflowed the solder by over heating it. now by removing that added pressure, the onlything left holding it together is solder. besides we are only talking about a few bucks.