Audio/Control Head Replacement - Sony AV-3420CE Service Manual

Preamplifier Check
20. It is also necessary to check the frequency
response of the preamplifiers. See Sec. 5-9.
Dihedral Check ©
The two video heads should be positioned
exactly 180 degrees apart. The relative angle can be
measured by observing the monitor screen.
21. Play back the alignment tape.
Fig. 7-11 Head dihedral adjust screw
head mounting screw
adj.
screw (B)
head base
dihedral
adj.
screw
mounting upper drum
cut-out
Fig. 7-13 Dihedral adjustment (2)
7-6
22. Observe the monitor screen, especially on the
top edge, to see if there is any sync displace-
ment as shown in Fig. 7-10. If this condition
observed on the top, proceed to Step. 23.
23. Position the video head assembly as shown
in Fig. 7-13. Install four angle adjustment
screws (SONY Part No. 3-618-904-00) shown
in Fig. 7-11 into both heads as shown in
Fig. 7-12. Thread them in until slightly snug.
Do not exert force. ,
CAUTION
DO NOT TOUCH HEAD MOUNTING SCREW.
See. Fig. 7-12.
24. Position B head (with red paint on the tip)
to the adjusting position.
25. Turn (a) screw in Fig. 7-12 CCW % turn and
(b) screw CW % turn.
26. Play back the video alignment tape again and
observe the top of the picture. If the amount
of displacement has decreased, repeat Step 25
until the displacement is invisible. If the
amount of displacement has increased, proceed
to Step 27.
27. Turn (a) screw in Fig.7-12 CW by % turn
and (b) screw CCW by % turn. Repeat
Steps 26 and 27 until displacement becomes
invisible.
28. Remove the four adjusting screws.
7-4, AUDIO/CONTROL HEAD REPLACEMENT
Replace audio/contro!l head when it is worn,
has open coils or is damaged. The head has the audio
reoced/playback portion at the top, and the control-
signal record/playback portion at the bottom.
1. Unsolder the leads at the rear of the head.
2. Remove the screws A and B in Fig. 7-14. Do
not loosen the screws in the long slots.
3. Lift the head assembly off the mounting plate.
4. Place the new head assembly on the mounting
_plate and install the two screws from the
bottom.
5. Install the head mounting plate assembly using
the original screws A and B in Fig. 7-14.