JVC DD-9 A - Electrical Circuit Adjustment Procedure; Decoder (playback) calibration Dolby C adj.; Adjusting playback level; Playback frequency response

DD-9A/B/C/E/J/U
= FL P.W. Board (Parts Ass‘y side view)
Va
Front
For FLO cB level adjustment
(Turning in the direction of the
arrow increases the levels.)
VR701 U VR501 U VR601
L R
Lo
Fig. 16
{1V] Electrical circuit adjustment procedure
The DD-9 employs a combination record/playback head,
thus permitting monitoring the sound being recorded.
For adjustment, playback of the recorded sounds is there-
fore possible simply by switching the MONITOR switch
from SOURCE to TAPE. (It is unnecessary to rewind the
tape.)
In the steps marked by an asterisk (*), adjustment should
be performed, however, only checking is sufficient with
steps other than those.
: Adjusting | Standard
Decoder
(playback)
2,533 Bes
PB level
adj.
1. Off the Dolby NR switch.
2. Apply a 400 Hz signal to PB head termi-
For FL —20 dB level adjustment
(Turning in the direction of the
arrow increases the levels.)
Adjustment should be performed in the order of steps, 1,
Perform this adjustment with the Dolby C NR
—2.5 dBs
switch set to OFF and output level control set to maximum.
calibration nal (PB level adj. VR set to some position). | VRAO1 —2.5 dBs
Dolby C Adjust input signal so that TP101 output BO1
adj. level becomes —2.5 dBs.
3. Adjust VRAO1 and BO1 so that TP102
output level becomes —2.5 dBs.
PB Kead EQ amp Dolby C circuit
ICAOI 1cBor
PB levet
adj Oo fey
TPIOI TPIO2
400H27(Y, VRAQ
2* | Adjusting 1. Play back the VTT-664 Reference tape | VR101, —4 dBs This adjustment becomes neces-
playback (1 kHz) with the tape select switch set to 201 (0.5 V) sary when a change in playback
level the SF/NORM position. level results (for example, due to
2. Adjust VR101 and VR201 until the LINE head replacement).
OUT becomes —4 dBs.
beat
3* | Playback
frequency pened
response
No. 4198
aH
bom
YH
© = connection
When soldering of pattern slit (R100, C100)
open as 1 > 2 > 3 steps, gain of 10 kHz fre-
quency response increases 0.5 dBs with one
step.
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