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.
Wanting to repair a neighbours tape recorder I needed the necessary information, it makes it easier. Although the service manual is described as "Language : English" To my dismay I found that it is entirely written in German, a language I do not understand. At least I now have the schematics which will help of sorts. I may not use this service again due to the laguage difficulty after all when it states English you do not expect it to be entirely in another language.
Text excerpt from page 15 (click to view)
SJ-48G SJ-51G SJ-55G
(2) Fixing of Fan motor and Fan
E.V cover Motor cushion Tapping screw
Fan motor cushion B Fan motor Fan motor cushion A
Fan clamp Motor shaft to be flush with front surface of hub. Propeller fan 100 Fan motor
(3) Wiring of Lead Wire
L-band C
B
C
B
Defrost thermo. ass'y D
Alminum tape Fuse ass'y
E.V cover sealer D
A
A Detail
Lead wire �WHITE�
B Detail
Bend this pin
D Detail
Fasten Defrost thermo. ass'y's wires as bellow. And set it inside of the four pins. Cut off to 7mm or shorter
Fuse ass'y Alminum tape E.V cover sealer D
C Detail
Set Lead wires of Defrost thermo. ass'y as shown. Fan motor cushion
7mm
L-band C
Horizontally Thermo. sensing element side (Silver metal)
Lead wires