Kenwood Audio Adjustment

Page 1

$KENwooD

in most power amplifier and receiver, audio Circuit of the unit
has 2 adiusting pornts - the one is bias Current adjustment,
the other center voltage adjustment

After tranSistor replacement, you should recheck the bias
current and center voltage

CENTER VOLTAGE ADJUSTMENT
1. Connect the VOM across the output terminal of
amplifier
2 Turn the center-voltage adjusting potentiometer so that
the VOM's readings half of + Vcc
Some units have no potentiometers for center voltage

CENTER VOLTAGE

MAiN AMP (5215)
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LEFT SPEAKER

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VOM

Adjustment Points in Schematic

half of Van

Alllllll AIIJIISIMEHT

BIAS CURRENT ADJUSTMENT

There are several methods for bias current adjustment
The most accurate method for adjusting bias current is
measuring the voltage drop across the emitter resistor of
power transistors under no signal,

Method

ll Turn the Volume Control to its minimum posrtion so that
the power amplifier circuit has not input signal.

2 Connect the VOM across the emitter resrstor of power
transrstor.

3. Turn the bias-current adjusting potentiometer so that the
VOM's readings is proper value. (Refer to the bias-
current value table page Vlll.)

Ex. In case of 30 mA bias current

Re12><30 mA = VOMs readings

O.47S2><3O mA = 14.1 mV
l.e Turn the potentiometer so that the VOMs readlngs
is 14l mV

PROTECTION ADJUSTMENT
1 Connect the 852 dummy load to the output terminal of
amplifier
2 Connect oscilloscope across the dummy load and AG to
AUX jack
3 Turn the volume control knob of amplifier and attenuator
of AG so that waveform becomes overload operation
4 Change 451 dummy load to 89.
6 Turn the protection potentiometer at the point of
waveform becoming low
6 Reconnect 8S2 dummv load to both output terminal of
amplifier and drive amplifier under full power output:
Comfirm the protection doesn't work

Page 2

©KENwooD

In most power amplifier and receiver, audio circuit of the unit
has 2 adiusting pornts - the one is bias current adjustment,
the other offset voltage adjustment

After transistor replacement, you should recheck the bias
current and offset voltage

OFFSET VOLTAGE ADJUSTMENT
1, Connect the VOM across the output terminal of
amplifier
2 Turn the offset-voltage adjusting potentiometer so that
the VOM'S readings 0,
Some units have 2 potentiometers for offset voltage; the
one lS rough, the other fine

REAR PANEL
SPEAKERS (A.B4~1GQA+BB~16£1)
- A + - a +

When adjusting L-Ch,
change the connection
of the test equipment

Note:

Bras Current
meter (B31-
0125-05) or
VOM setting
volt range

BIAS CURRENT ADJUSTMENT

There are several methods for bias current adjustment.
The most accurate method for adjusting bias current lS
measuring the voltage drop across the emitter resrstor of
power tran5istors under no Signal

Math 0d

1. Turn the Volume Control to its minimum position so that
the power amplifier crrcurt has not Input Signal

2. Connect the VOM across the emitter resrstor of power
transrstor.

3. Turn the bias-current adjusting potentiometer so that the
VOM's readings is proper value, (Refer to the bias-
current value table)

Ex. In case of 40 mA bias current.

(Fle45 + Re47)><40 mA = VOM's readings
(0.479 + O,47fl)><40 mA = 376 mV

LEV Turn the potentiometer so that the VOM's readings
is 376 mV

DC voltmeter

BIAS-CURRENT VALUE TABLE

Alllllll AIIJIISTMENI

MODEL BIAS CURRENT MODEL BIAS CURRENT
KA-ZOOOA 30 mA KR-8140 15 mA
KA-2002 20 mA KR-8340 30 mA
KA-ZOOZA 20 mA KR-9340 50 mA
KA-2600 20 mA
KA-3004 20 mA KSQ-4OO 20 mA
KA-3344 20 mA
KA-4002 20 mA MA-5100 20 mA
KA-4004 10 mA MODEL-700M 50 mA
KA-5002 30 mA
KA-6004 10 mA
KA-7002 50 mA
KA»8004 20 mA
KA-8044 20 mA
KM-8002 50 mA
KR-33L 20 mA
KR-33SW 20 mA
KR-44SL 20 mA
KR-44SW 20 mA
KR-i 1 10 20 mA
KR-2120 20 mA
KR-2200 10 mA
KR-23OO 20 mA
KR-3130 20 mA
KR-3200 20 mA
KR-4050 20 mA
KR-4130 20 mA
KR-4140 20 mA
KR-4200 20 mA
KR-5150 30 mA
KR-517O 15 mA
KR-5200 20 mA
KR-5340 20 mA
KR-Bi 40 20 mA
KR-6160 20 mA
KR-6170 30 mA
KR-GZOO 20 mA
KR-634O 20 mA
KR»7200 20 mA
KR7340 30 mA
KR-7070 50 mA
KR-707OA 50 mA