JVC MX-GA9V Service Manual page 38

4.4 Tape recorder section
Items Measurement conditions
Confirmation Test tape
of head angle : VT710 (10kHz)
Measurement output terminal
: Speaker terminal
Speaker R (Load resistor : 6Ω)
: Headphone terminal
Confirmation Test tape
of tape speed : VT712 (3kHz) or TMT7036 (3kHz)
Measurement output terminal
: Headphone terminal
4.5 Reference values for confirmation items
Items Measurement conditions
Double tape Test tape : VT712 (3kHz)
speed Measurement output terminal
: Speaker terminal
Speaker R (Load resistance:6Ω)
measurement output terminal
: Headphone terminal
Difference
between the
forward and
reverse speed.
P.mecha and
R/P mecha
speed
Wow & flutter Test tape : VT712 (3kHz)
Measurement output terminal :
Headphone terminal
1-38 (No.MB011)
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Measurement method
1.Playback the test tape VT710 (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
VT712 (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 VT712
(3kHz) has been play back with the
playback mechanism.
When the test tape VT712 (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 VT712 (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).
Standard values Adjusting positions
Maximum output Adjust the head
azimuth screw only
when the head has
been changed.
Tape speed of VR301
decks (A and B)
:3,000Hz ±60Hz
Standard values Adjusting positions
4,800+400/-300Hz Playback
mechanism side
60Hz or less Both the playback
and recording &
playback mechanism
with in 0.25% Both the playback
JIS(WTD) and recording &
playback mechanism