Cassette Amplifier Section - JVC RC-BZ5LB Service Manual

RC-BZ5LB/BZ5RD
RC-BZ6BU

Cassette amplifier section

Item Conditions
Head azimuth
• Test tape:
adjustment
VT702(8 kHz)
• Test output from:
Speaker terminal
(with 3 Ω load)
Tape speed,
• Function selector:
Wow & flutter
TAPE
check
• Test tape:
VT712 (3 kHz)
•Test output from:
Speaker terminal
(with 3 Ω load)
Playback • Function selector:
output check TAPE
• Test tape: VT722,
VT724 (1 kHz)
• Test output from:
Speaker terminal
(with 3 Ω load)
Playback
• Function selector:
frequency TAPE
response • Test tape: VT738
check
• Test output from:
Speaker terminal
(with 3 Ω load)
REC/PB
• Function selector:
sensitivity TAPE
check • Mode: Recording
• Test input to:
CN301
1-16
Adjustment & Confirmation Method
1. Play back the test tape VT702 (8 kHz sig-
nal).
2. Adjust the azimuth adjusting screw so that
phase difference between R and L chan-
nels is minimum with the output level that
is the maximum level plug less than 2 dB
in the FWD and REV mode.
After the adjustment apply screw sealant
onto the azimuth adjusting screw for more
than half the screw head.
3. If the head azimuth is still maladjusted, re-
adjust it with the azimuth adjusting screw
alternately in the FWD and REV modes.
1. Play back the end portion of the test tape
VT712 (3 kHz signal).
2. At that time check to see if the frequency
counter reads 2940 to 3090 Hz. If not,
adjust the semi-fixed resistor inside the
motor to obtain the specified frequency.
3. Wow and flutter must be 0.38 % or less
(unweighted).
1. With the test tape VT722 (1 kHz signal)
being played back, confirm that the speaker
output is 2.1 W or more with 10 % distor-
tion.
2. With the test tape VT724 being played
back, confirm that the deviation between
R-ch and L-ch outputs is less than 3 dB.
With the test tape VT738 being played back,
confirm that the deviation between 1 kHz and
125 Hz signals is 6 ± 3 dB and that between
the 1 kHz and 8 kHz signals is 0 ± 4 dB.
With the input of 1 kHz, –20 dBs signal to the
test point CN301, confirm that the level dif-
ference between the recording and playback
is 0 ± 3 dB or less.
Standard Value Adjusting Point
• Output: Max. Azimuth adjusting
level plus less screw (after head
than 2 dB replacement only)
• Phase differ-
ence between
R & L ch:
Minimum
Tape speed (with
semi-fixed resistor
Frequency: inside motor)
2940-3090 Hz
0.38 % or less
(unweighted)
• Speaker output
with 10 %
distortion:
2.1W or more
• Deviation be-
tween R & L ch
outputs:
3 dB or less
• Deviation
between 1 kHz
& 125 Hz:
6 ± 3 dB
• Deviation
between 1 kHz
& 8 kHz:
0 ± 4 dB
• Level difference
between
REC & PB:
0 ± 3 dB or less