JVC MX-J300 Service Manual page 26

MX-J300
Reference values for confirmation items
Items Measurement
conditions
Double tape
Test tape
speed
:VT703(10kHz)
Measurement
output terminal
:Speaker terminal
Speaker R
(Load resistance:3ohm)
measurement
output terminal
:Headphone terminal
Difference
between the
forward and
reverse speed.
P.mecha and
R/P mecha
speed
Wow & flutter
Test tape
:VT703(10kHz)
Measurement
output terminal
:Headphone terminal
Reference values for electrical function confirmation items
Items Measurement
conditions
Recording
*Recording and
bias frequency
playback side forward
or reverse
*Test tape
:TYP AC-514
*Measurement
terminal BIAS TP on
P.C.board
Eraser current
*Recording and
(Reference
playback side forward
value)
or reverse
*Recording mode
*Test tape
:AC-514 and AC-225
Measurement terminal
Both of the eraser
head
1-26
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).
Measurement method
1.While changing over to and from BIAS 1 and 2,
confirm that the frequency is changed.
2.With the recording and playback mechanism.
load the test tape (AC-514 to TYP ),and set the
mechanism to the recording and pausing
conditions in advance.
3.Confirm that the BIAS TP frequency on the
P.C.board is 100kHz 6kHz.
1.With the recording and playback mechanism,
load the test tapes(AC-514 to TYP and AC-225
to TYP ),and set the mechanism to the recording
and pausing condition in advance.
2.After setting to the recording conditions, connect
1Mohm in series to the eraser head on the
recording and playback mechanism side, and
measure the eraser current from both of the eraser
terminal.
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
Adjusting
Standard
positions
values
100kHz
+9kHz
-7kHz
TYP
:120mA
TYP
:75mA