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'D-W20A/B/C/E/G/J/U
4, Electrical circuit adjustment procedure
In the steps marked with an asterisk (*), adjustment should be performed after replacing the heads.
Perform this adjustment with the NR switch set to OFF.
Check and Adjustment
Signal input: LINE IN
1 kHz, Cal. —40 dB
+5.7dB+1dB
DOLBY B
(Rec)
Sel [Cal evel: 400 Hz, 68s
(BIAS, CUT) |Output terminal: NR. TP
DOLBY c
P
Adjusting
Standard
Step
Item
Adjustment
point
value
Remarks
*2
|Confirming
| Play back VTT644 (or VTT724), then |DeckA
When the head is replaced, adjust
confirm that the level at LINE OUT is [L:R153,R154/Bi|-8+ 1.5dB
(Al—7dBs+1.5dB,{B]—8dBs+1.5dB alerlee
eC
| playback gain
playback gain level.
Deck A
L:R153 cut by +1dB
R154 cut by —1dB
R:R253 cut by +1dB
R254 cut by —1dB
Deck B
L: R122 cut by +1dB
R125 cut by —1dB
R:R222 cut by +1dB
R225 cut by —1dB
bias
frequency
10 (No..4256)
C925,Lead through a 1.2 MQQ resistor,
then adjust L901 so that the counter
reads 95 kHz.
*3. | Playback
Deck A: Play back VTT739, then con-
B72 cut by —1dB
frequency
firm
that
the level of 1 kHz
and
IL:
B73 cut by —2dB
response
10 kHz signals is 0.5 + 2 dB.
R:VR203 | Deck B:
B75 cut by —1dB
Deck B: Before adjustment, disconnect
|DeckB
0+2dB
B76 cut by —2dB
B72, B73 (L-ch) and B75, B76
L:872,873
(R-ch) so that the outputs of 1 KHz
|L:B75,B76
and 10 kHz signals are flat.
a
Adjusting
Connect the frequency counter to the | L901
95 kHz
METAL
Position
+ 10%
=
kHz
outputs
satisfy
the standard
values with respect to 1 kHz output.
Response (dB)
a
Decrease in high frequencies
QO
50 Hz
1 kHz
ode
Increase in high frequencies
Low bias current
Appropriate bias current
High bias current
12.5 kHz Frequencies
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