This document is just what I was looking for, it´s very useful, it contains adjustment procedures for the final stage of the power amp and also
has a complete wiring diagram and description of the main semiconductors used in the design.
Text excerpt from page 9 (click to view)
C-1. Bad playback quality (1)
Noise appears on the playback screen.
Is noise diminished by tracking adjustment. YES Noise band is trembled up and down? YES Is there CTL pulse at IC601 pin#97? YES
NO Re-adjust PATH.
Noise appears on the screen even though changing tape.
YES Re-adjust PATH.
Is the height of CTL HEAD normal? No dust?
Re-adjust the height of AC HEAD. Remove the dust.
Is there problem in CTL Input circuit and amplifier.