JVC MX-GT91R Service Manual page 28

MX-GT91R
Tape recorder section
Items Measurement
conditions
Confirmation
Test tape
of head angle
:TMT7036(10kHz)
Measurement
output terminal
:Speaker terminal
Speaker R
(Load resistor:6 )
:Headphone terminal
Confirmation
Test tape
of tape speed
:VTT712(3kHz) or
TMT7036(3kHz)
Measurement
output terminal
:Headphone terminal
Reference values for confirmation items
Items Measurement
conditions
Double tape
Test tape
speed
:TMT7036(10kHz)
Measurement
output terminal
:Speaker terminal
Speaker R
(Load resistance:6 )
measurement
output terminal
:Headphone terminal
Difference
between the
forward and
reverse speed.
P.mecha and
R/P mecha
speed
Wow & flutter
Test tape
:TMT7036(10kHz)
Measurement
output terminal
:Headphone terminal
1-28
Measurement method
1.Playback the test tape TMT7036(10kHz).
2.With the playback mechanism or recording &
playback mechanism, adjust the head azimuth
screw so that the forward and reverse output
levels become maximum.After adjustment,lock
the head azimuth at least by half a turn.
3.In either case,this adjustment should be
performed in both the forward and reverse
directions with the head azimuth screw.
<Constant speed>
Adjust VR301 so that the frequency counter reading
becomes 3,000Hz 60Hz when playing back the
test tape VTT712(3kHz)with the playback mechanism
or playback and recording mechanism after ending
forward winding of the tape.
Measurement method
After setting to the double speed motor, confirm
that the frequency counter reading becomes
4,800+400/-300Hz when the test tape VTT712
(3kHz) has been play back with the playback
mechanism.
When the test tape VTT712(3kHz) has been played
back with the playback mechanism or recording and
playback mechanism at the beginning of forward
winding, the frequency counter reading of the
difference between both of the mechanisms should
be 6.0Hz or less.
When the test tape VTT712(3kHz) has been played
back with the playback mechanism or recording and
playback mechanism at the beginning of forward
winding the frequency counter reading of wow &
flutter should be 0.25% or less(WRMS).
Adjusting
Standard
positions
values
Adjust the head
Maximum
azimuth screw
output
only when the
head has been
changed.
VR301
Tape speed
of decks
(A and B)
:3,000Hz
60Hz
Adjusting
Standard
positions
values
4,800+400/
Playback
-300Hz
mechanism side
60Hz or
Both the playback
less
and recording &
playback
mechanism
with in
Both the playback
0.25%
and recording &
JIS(WTD)
playback
mechanism