Adjustment; Measurement Instruments Required For Adjustment; Measurement Conditons; Radio Input Signal - JVC DX-T7 Service Manual

4.1 Adjustment method

4.1.1 Measurement Instruments Required for Adjustment

(1) Low frequency oscillator
This oscillator should have a capacity to output 0dBs to
600Ω at an oscillation frequency of 50Hz-20kHz.
(2) Attenuator impedance : 600Ω
(3) Electronic voltmeter
(4) Distortion meter
(5) Frequency counter
(6) Wow & flutter meter
(7) Test tape
VT703 : Head azimuth
VT712 : Tape speed and running unevenness(3kHz)
VT724 : Reference level (1kHz)
(8) Blank tape
TYPE l: AC-225
TYPE ll: AC-514
(9) Torque gauge : For play and back tension
FWD(TW2111A), REV(TW2121a) and
FF/REW(TW2231A)
(10) Test disc: VT-501, CTS-1000

4.1.2 Measurement conditons

Power supply voltage:
AC110V / AC127V / AC220VAC230V ~ AC240V
(Adjustable with the voltage selector)50Hz / 60Hz
Reference output:
Reference frequency and
input level:
Measurement output terminal:
Load resistance:

4.1.3 Radio Input signal

AM frequency:
AM modulation:
FM frequency:
FM frequency deviation:
SECTION 4

ADJUSTMENT

Speaker : 0.775V/4Ω
Headphone : 0.077V/32Ω
1kHz, AUX : -8dBs
at Speaker J200
4Ω
400Hz
30%
400Hz
22.5kHz
4.1.4 Tuner section
FM Band cover: 87.5 - 108.0MHz
AM Band cover: 531 - 1,710kHz (at 9kHz)
530 - 1,710kHz (at 10kHz)
Voltage applied to tuner:
Reference measurement
output:
Input positions:
4.1.5 Standard measurement position of volume
Function switch
Beat cut switch
Super Bass/Active hyper Bass
Bass Treble
Adjustment of main volume to reference output VOL : 28
Precautions for measurement
(1) Apply 30pF and 33kΩ to the IF sweeper output side and
0.082µ F and 100kΩ in series to the sweeper input side.
(2) The IF sweeper output level should be made as low as
possible within the adjustable range.
(3) Since the IF sweeper is a fixed device, there is no need
to adjust this sweeper.
(4) Since a ceramic oscillator is used, there is no need to
perform any MIX adjustment.
(5) Since a fixed coil is used, there is no need to adjust the
FM tracking.
(6) The input and output earth systems are separated. In
case of simultaneously measuring the voltage in both of
the input and output systems with an electronic voltmeter
for two channels, therefore, the earth should be connect-
ed particularly carefully.
(7) In the case of BTL connection amp., the minus terminal
of speaker is not for earthing. Therefore, be sure not to
connect any other earth terminal to this terminal. This
system is of an BTL system.
(8) For connecting a dummy resistor when measuring the
output, use the wire with a greater code size.
(9) Whenever any mixed tape is used, use the band pass fil-
ter (DV-12).
+B : DC5.7V
VT : DC 12V
26.1mV(0.28V)/3Ω
AM : Standard loop antenna
FM : TP1 (hot) and TP2 (GND)
to Tape
to Cut
to OFF
to Center
(No.MB368)1-51