Thanks you very much for this "hard to find" service manual.
Will help a lot in repairing this receiver.
Text excerpt from page 6 (click to view)
Removing the main board (See Fig.14)
Prior to performing the following procedure, remove the top cover, the rear panel and audio board. 1. Cut off the tie band fixing the harness. 2. Disconnect the harness from connector CN811 on the power supply board respectively. 3. Disconnect the harness from connector CN881 on the main board. 4. Remove the four screws I and the two screws J attaching the main board.
Main board CN881
Removing the Heat sink (See Fig.15 and 16)
1. Remove the two screws L' attaching the heat sink from the rear side of main board. 2. Disconnect the connect CN701, CN702, CN703, CN705 and CN706 on the main board. 3. Remove the ten screws K and four screws L attaching the heat sink.