Adjustment Method - JVC MX-J270V Service Manual

MX-J270V

Adjustment method

Measuring devices necessary for
adjustment
1. Low-frequency oscillator
It must have the ability to output 600ohm from 0
dBs at an oscillation frequency of 20 Hz - 50 Hz.
2. Attenuator impedance: 600ohm
3. Electronic voltmeter
4. Distortion meter
5. Frequency counter
6. Wow and flutter meter
7. Test tapes
VT-712: tape speed and rotational distortion (3 kHz)
VT-724: standard level (1 kHz)
VT-703: head angle adjustment (10 kHz),
or use VT-73
VT-739: reproduction of frequency characteristics
(1 kHz, 63 Hz, 10 kHz)
8. Blank tape
Type I : AC-225 (TDK-AD)
Type II : AC-514 (TDK-SA)
9. Torque gauge: Tension gauge for playback,
fast-forward and rewind.
FWD (TW211A), REW (TW212A)
and FF/REW (TW2231A)
Specifications for measurement
Power supply voltage .......AC 110 to 240 V (50/60 Hz)
Standard output .....................Speaker: 0.775 V/6ohm
Standard frequency and input level
Input level for reproduction of recording characteristics
Measuring output terminal ................. Speaker: JA303
Load resistance .................................................. 6ohm
Radio input signal
AM frequency ................................................... 400 Hz
Degree of modulation in AM band ....................... 30%
FM frequency ................................................... 400 Hz
Frequency deviation in FM band ................... 22.5 kHz
1-22
Headphone:0.245V/32ohm
................ 1 kHz: AUX: -8 dBs
................... AUX: -28 dBs
Tuner section
Voltage input to the tuner ..................... +B: DC 5.7 V
Standard measuring output ..26.1 mV (0.28 V) /3ohm
Input locations ................ AM: standard loop antenna
FM: TP1 (hot) and TP2 (GND)
Standard settings for measuring
volume
Sound ................................................................. OFF
Effective hyper bass ........................................... OFF
Volume adjustment ...................................... VOL. 23
Precautions for measuring
1. Input 30 pF and 33 kohm to the IF sweeper output
and 0.082 F and 100 kohm to the sweeper input,
respectively.
2. Lower the output level of the IF sweeper as much
as possible in the adjustable range.
3. The IF sweeper needs no adjustment as it is a
fixed component.
4. It is not necessary to perform any kind of
adjustment on the MPX, as a ceramic oscillator is
used for measuring.
5. FM tracking adjustment is not necessary as a fixed
coil is used.
6. The grounding circuit is separate from the input
and output. Therefore, be sure to connect to ground
carefully when measuring both the input and output
voltages simultaneously using 2 channels of the
electronic voltmeter.
7. The speaker's minus terminal cannot be connected
to ground when using a BTL format amplifier.
Therefore, do not connect any type of ground wire
to this terminal. The OTL format is used with this
system.
8. Use a large wire to connect to the dummy
impedance generator when measuring the output.
9. Be sure to use a band pass filter (DV-12) when
using mixed tape.
VT: DC 12 V