Thanks you very much for this "hard to find" service manual.
Will help a lot in repairing this receiver.
Text excerpt from page 56 (click to view)
TROUBLESHOOTING GUIDES (Continued)
When change the channel broadcast signal is not received. YES
Is the output of pin , of IC601 71 72 normal? YES
Check the Video output Buffer Q101.
YES Check the Video, Audio output signal of pin 8, 20 of TMI BLOCK (RF101). NO Check the Video IC. Check the IC601. YES Check the video output signal pin qof IC301. NO YES Check the video signal pin of s IC601. NO