Main Adjustment; Amplifier Adjustments - JVC PC-V77 Service Manual

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~ Main Adjustment
• Amplifier adjustments
Conditions
Power supply voltages : DC 1 2 V, Timer 1.5 V SEA controls
Tape select
Tapes used
Input levels
Output levels
Item
Head azimuth
adjustment
Tape speed
adjustment
Checking wow
& flutter
Playback
output level
Confirming
playback
frequency
response
Recording bias
frequency
Rec /Play
frequency
response
Rec /play
output
adjustment
(from battery)
AUX 8 dBm, MIC 48 dBm
Speaker 0 dBm / 6
n
Headphones 0 dBm/ 32
n
Tape used Adjustment/check method
VTT703 Maximize outputs of decks A and B; adjust to
(10kHz)
minimize phase difference between left and right
channels.
To adjust deck A, adjust FWD first , then REV .
After adjustment, apply screw locking
compound.
[ Fine adjustment after assembly should be done
with the head cover removed .
VTT712 After normal speed adjustment , perform double
(3 kHz)
speed adjustment
1. Adjust the normal speed of deck A to 3000
with VR851 .
2. Check if Deck
cru
is at 3000 Hz
+
10Hz.
3. To confirm high speed mode, play back Deck
cru,
then set Deck
lA]
to record mode.
VTT712 Deck B : 0 .35 %
(3 kHz) Deck A : 0.40% (JIS RMS) or less
VTT724 Adjust VR10l , VR102 (deck A) and VR201 ,
(1 kHz) VR202 (deck B) so that the output of TP151 ,
TP251 and TP751 are - 21 dBm
VTT739 With respect to their outputs at 1 kHz, the out-
puts at TP151 and TP251 should be - 5
±
3 dB
at 63 Hz, and - 1
±
3 d8 at 10kHz.
(TS -8) Set beat cut switch S 7 21 to position 1 and ad -
Normal tape just the oscillating frequency of C724 to 68
±
1 kHz with L 721. (Connect a 100 {) resistor in
series when measuring .)
(TS -8) Deck A: Adjust VR 122 (L ch) and VR222 (R ch)
Normal tape
so that the rec /play output of an input signal
- 20 dB with respect to the reference level at
1 kHz is - 0 dB
±
1 dB at 10kHz.
Deck B : Same as deck A .
Measure outputs from TP151 and TP251.
(TS -8) Adjust VR 121 (L ch) and VR221 (R ch) so that
Normal tape the level when recording and playing back an
AUX (CD) IN signal - 20 dB with respect to the
reference level is - 0 dBm
±
1 dB.
Center
Normal
PC -V77 A/B /E/G/UN
Recording normal tape TS -8 (UR)
chrome tape TS -6
metal tape TS -7
Switch setting
Adjustment location
Tape/normal Deck A : Adjust FWD
speed then REV
Deck B
Tape/Normal VR851
speed
High speed
Tape /Normal
speed
Tape /Normal Deck A
speed L ch : VR10l
R ch : VR201
Deck B
L ch: VR102
R ch: VR202
Tape /Normal
speed
S721 L721
(Beat cut)
2 : 66 kHz
3 : 68 kHz
L ch : VR 122
R ch : VR222
L ch : VR 121
R ch: VR221
(No. 1740) 7