I would try wiggling the display connectors to the MPU to see if it's just a poor connection at the plug(s). On my 6803 I ended up repinning most of the connectors due to flaky and inconsistent connections.
Also verify that your MPU is working properly via the power-on flashes from the MPU LED. You should get 9 flashes. You can also test the sound board with the on-board button.
I can't tell by the pics but make sure you clip that battery off the board and install an NVRAM. The ram is already socketed so it's a simple no-solder install.
