Electrical Performance - JVC UX-T77 Service Manual

Electrical Performance

Measurement
Items
conditions
Adjustment of Mode: Forward or
recording bias reverse mode
current Recording mode
(Reference Test tape
Value) : AC-514 to TYPE
and AC-225 to
TYPE
Measurement output
terminal
: Both recording and
headphone terminals
Adjustment of Reference frequency
recording and : 1kHz and 10kHz
playback (REF.: -20dB)
frequency Test tape
characteristics : AC-514 to TYPE
Measurement input
terminal
: OSC IN
Reference Values for Electrical Function Confirmation Items
Measurement
Items
conditions
Forward or reverse
Recording
Test tape
bias
: TYPE (AC-514)
frequency
Measurement
terminal : BIAS TP on
P.C. board
Forward or reverse
Eraser
Recording mode
current
Test tape
(Reference
: AC-514 to TYPE
value)
and AC-225 to
TYPE
Measurement
terminal : Both of the
eraser head terminals
Measurement method
1 With the recording and playback
mechanism, load the test tapes (AC-514 to
TYPE and AC-225 to TYPE
the mechanism to the recording and
pausing condition in advance.
2 After connecting 100 in series to the
recorder head, measure the bias current
with a valve voltmeter at both of the
terminals.
3 After resetting the [PAUSE] mode, start
recording. At this time, adjust VR31 for Lch
and VR32 for Rch so that the recording
bias current values become 4.0 A (TYPE
) and 4.20 A (TYPE
1 With the recording and playback
mechanism, load the test tapes (AC-514 to
TYPE ), and set the mechanism to the
recording and pausing condition in
advance.
2 While repetitively inputting the reference
frequency signal of 1kHz and 10kHz from
OSC IN, record and playback the rape.
3 While recording and playback the test tape
in TYPE , adjust VR31 for Lch and VR32
for Rch so that the output deviation
between 1kHz and 10kHz becomes
-1dB 2dB.
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 TYPE ), and set the
mechanism to the recording and pausing
condition in advance.
3 Confirm that the BIAS TP frequency on the
P.C. board is 100kHz 6kHz.
1 While recording and playback mechanism,
load the test tapes (AC-514 to TYPE
and AC-225 to TYPE ), and set the
mechanism to the recording and pausing
conditions in advance.
2 After setting to the recording conditions,
connect 1W in series to the eraser head on
the recording and playback mechanism
side, and measure the eraser current from
both of the eraser terminals.
Standard
Values
AC-225
: 4.20 A
AC-514
), and set
: 4.0 A
).
Output
deviation
between
1kHz and
10kHz
: -1dB 2dB
Standard
Values
100 kHz
6 kHz
TYPE
: 120 mA
TYPE
: 75 mA
UX-T77
Adjusting
positions
L ch
: VR31
R ch
: VR32
L ch
: VR31
R ch
: VR32
Adjusting
positions
1-19