WS-55805 DTV mode

Larry, Before I got the blinking green light of death on my Mitsubishi WS-55805 I made the (apparent) mistake of entering the service mode. I wanted to do the convergence alignment described in the manual which I thought might be better than the one accessible in the regular menus. I changed the DTV mode from Auto to HD thinking that this is the mode I wanted. The display was showing my external hdtv receiver channel which was connected to the component inputs (not input 3) for the dtv input. When HD was selected the tv display from my receiver looked like it lost lock. So I put the DTV mode back to Auto. Before the green blinking light of death occurred the tv displayed a message which said that I needed to power off the DTV receiver and reapply power, which I did, but still nothing showed up on the tv (blue screen). My tv thinks that it has a DTV receiver and displayed 99.9 as the channel. I remember that on the advanced settings display, on the Input Assignment menu, that the DTV used to show YPrPb as one selection. Now it just shows RGB or Off. The service manual even shows this as the default selection. My question is this (finally), how do I regain the YPrPb setting and get these inputs working again (after I replace some caps I guess)??? Is there a menu selection in the service mode which tells the tv that it should look for a signal on the component inputs and not a channel on an imaginary receiver? I believe these tv's had a mfr option to buy the internal receiver at a later date. Not sure if this happened. If they did they had to have some menu selection that told the tv that it had the option. Maybe setting the DTV mode to HD and back to Auto didn't reset this other option? Thanks for any help, sorry for the long message.