Awesome manual. Complete diagrams of all board assemblies as well as how to get to each part of the t.v. down to the individual screws and their locations. Get it.
This is exactly the service manual I needed.
Complete with all schematics, partslists, PCB layouts and alignment instructions.
This manual covers both the T-4970 en T-488F Onkyo tuner.
Text excerpt from page 144 (click to view)
...from previous page
B
Remove the Main digital board and check the resistance to ground at the Vias points which are the path for the audio signals.
Is the measured resistance below 19 Kohm?
Yes
Repair/Replace the Digital Main board.
No
Repair/Replace the Terminal board.
The next pictures show the location of the Vias in the Main-Digital Board. These Vias are the paths for the audio signals. Check the waveforms and/or the resistance at these Vias. Digital Main Board,