After removing the BNC input connectors it was fairly easy to make some measurements. My former analysis apparently was correct. The two circled resistors are open >20Meg resistance in channel one. The upper resistor is the one that caused the most damage in channel two. Actually the lower resistor in channel two still measures 164k Ohms. As burned as it is i don't trust that to be the original value. There appears to be nothing else that has suffered. I do believe all the damage was confined to the front end, remember the edges of a square wave gets through fine, and a sine waves amplitude is proportional to frequency as one would expect if the input were ac coupled with a small capacitor. Anyway, I feel I could fix this beast if..........I only knew the value of the one (upper) resistor. It would be nice to verify the lower resistor value also, since the one in channel two has been stressed badly.
I am assuming there is no hope of obtaining a schematic for this board (made in China), just wondering if anyone out there has had to open one of these scopes, and when trying to troubleshoot has measured the value of this resistor? My only other option is to, someday, obtain another one of these scopes, tear it down and measure the resistor value. Not a pleasant thought, as this scope was not made to disassemble for sure.