JVC TD-W777A - Main Adjustments; Equipment and Measuring Instruments; Mechanism Adjustment Procedures

TD-W77 7 A/B/C/E/G/J/U
Main Adjustments
1. Equipment and measuring instruments used for adjustments
1) Electronic voltmeter 7) Distortion meter (bandpass filter)
2) Audio frequency oscillator 8) Torque testing cassette gauge, CGT-N
(range: 50—20 kHz and output 0 dB with impedance of 600 2) 9) Wow flutter meter
3) Attenuator (impedance: 600 22) 10) Frequency counter
4)Standard tape for REC/PB
Maxell UD1 (TS-9) — Normal (SF) tape
TDK SA ’ — Chroma (SA) tape — or equivalent = Power sources
JVC ME — Metal tape Set the line voltage selector switch to 240 V/230 V/
5) Reference tape for playback (JVC Test Tape) 220 V/127 V/120 V/110 V according to your local
VTT712 (for tape speed, wow flutter adj.) voltage.
V11724
(for
playback
level)
AC
240
V,
50/60
Hz
(TD-W777A/B)
VTT739 (for playback frequency response) AC 220 V, 50/60 Hz (TD-W777E/G)
6)
Resistor
600
Q
(for
attenuator
matching)
AC
230
V/127
V/110
V,
50/60
Hz
(TD-W777U)
2. Mechanism adjustment procedure ® Notice: 0 dBs = 0.775 (V)
Item | Adjustment Adjus ring Standard Remarks
point value
Adjusting 1. Connect a frequency counter to the | Deck {A): Normal For adjusting high speed, TP bus
motor speed LINE OUT terminals. Normal; VR702 speed: wire should be grounded. Adjust
2. Play back the VTT712 test tape. High; VR701 Deck [A]; high speed after perform normal
3. Adjust for deck [A]: 3000 + 15 Hz! speed.
Adjust VR701 for normal speed at {Deck [B): Deck [B];
3000 Hz, and VR702 for high speed at | Normal; VR704| 3000 +15 Hz
6000 Hz. High; VR703
High speed:
Adjust for deck [B]: Deck (Al:
Adjust VR703 for normal speed at 6000 +15Hz
3000 Hz, and VR704 for high speed at Deck [B];
6000 Hz. 6000 +15 Hz
Checking Connect a wow and flutter meter to LINE 0.15% If the reading becomes moving
wow and OUT terminals. Play back the VTT712 (WRMS) jvalue even if confirming to the
flutter test tape. Check to see if the reading of standard, a reclaim may be raised.
the meter is within 0.15% (WRMS). Repairs are necessary.
Checking Employ a torque testing cassette tape for 30—70 gr-cm | If the standard torque is not ob-
playback
the
checking,
or
remove
the
cassette
cover
tained,
replace
the
take-up
disk
torque
and
use
a
torque
gauge.
|
assembly.
Checking
Measure
the
torque
in
the
fast
forward
70—200
gr-cm|
If
the
standard
torque
is
not
ob-
fast
forward
|
mode
in
the
same
manner
as
in
the
above.
tained,
perform
the
following.
torque
1.
Clean
the
capstan
belt,
the
idler circumference, the motor
pulley, the take-up reel disk
circumference, the flywheel
circumference, etc.
2. Replace the belt and idler.
Checking
Measure
the
torque
in
the
rewind
mode
ies
gr-cm|
If
the
standard
torque
is
not
ob-
rewind
in
the
same
manner
as
in
the
above.
tained,
clean
the
capstan
belt,
torque idler, motor pulley, flywheel cir-
cumference, rewinding idler cir-
cumference, left reel disk circum-
ference, etc.
(No. 4292) 9