JVC SR-VS30U Service Manual page 15

4.5 Electrical adjustment procedure
Item
1 Checking
DOLBY
Signal input: LINE IN Cal. level :
circuit
400 Hz, -8 dBs
(Rec. mode)
Output terminal TP : NR IC831 53 and 8
(BIAS-CUT)
pin.
Item Conditions
*2 Play back Test tape :
level VT727 (400 Hz)
adjustment
*3 Play back Test tape :
frequency VT742
response (63 Hz, 1 kHz,
adjustment 12.5 kHz)
*4 Bias Frequency counter
frequency TP: CN845 pin 1
adjustment Tape: Metal
Mode: REC
Frequency counter
input impedance:
more than 470kohm
(see 3.3 Location of
adjustment.)
*5 Slave DC. Voltmeter
oscillation TP: CN845
(HX PRO) Lch (pin 3 - 4)
adjustment Rch (pin 3 - 5)
Check and Adjustment
DOLBY B
(Rec)
DOLBY C
(Rec)
Adjustment and Confirmation
Play back VT727 in FWD mode, then confirm
that the level at LINE OUT is -4.5 dBs
Adjust VR112/VR212 and VR117/VR217 so that
LINE OUT level becomes -4.5 dBs.
Difference level between Lch and Rch must less
than 0.5 dB at LINE OUT.
Confirm that difference playback level between
FWD and REV modes within 1.5 dB.
Play back VT742 test tape, and adjust VR116,
VR216 (deck B) and VR111, VR211 (deck A) so
that deviation of 12.5 kHz to that of 1kHz is
0.5 0.5 dB (deck A) and 0
Then play back VT742 test tape to confirm that
deviation of 63 Hz to 1 kHz is +2
Connect frequency counter to the pin 1 of CN845
and adjust L8401 so that the counter reads
95 kHz.
This step must be performed after the bias
frequency adjustment.
Load a metal tape and set the deck to the
recording mode.
Adjust L1401 and L2401 to minimize respective
DC voltage of CN845 (pin 3 - 4) at Lch and (pin 3
- 5) at Rch.
Input signal
(Frequency, level)
1 kHz, Cal. - 40 dB
5 kHz, Cal. - 20 dB
1 kHz, Cal.
1 kHz, Cal. - 40 dB
5 kHz, Cal. - 20 dB
1 kHz, Cal.
Standard value
LINE OUT
0.5 dB. -4.5 dBs
Phone Out
-21 dB
+2.5 dB -1.5 dB
Difference level of
12.5 kHz from 1kHz
within 0.5
0.5 dB (deck B). (both decks A and
B)
3 dB. Difference level of
63 Hz from 1 kHz
within +2
95 kHz
Minimum
Output raise value,
deviation value
+5.7 dB 2 dB
+3.5 dB 1.5 dB
0 dB +0.5 dB -1.0 dB
+16.2 dB +3 dB -2 dB
+2.9 dB 2.5 dB
0 dB 1 dB
Adjust point
Deck B
0.5 dB L : VR117
R : VR217
Deck A
L : VR112
R : VR212
Deck B
L : VR116
0.5 dB R : VR216
Deck A
L : VR111
R : VR211
3 dB.
1 kHz Deck B
L8401
Deck B
L : L1401
R : L2401
(No.MB061)1-15