Kenwood KAC 819 Service Manual

Page 1

POWER AMPLIFIER

KAC-819 KENWOOD
SERVICE MANUAL

©2001-1 PRINTED IN JAPAN
851-7691-00 (4) 3376

Heat sink
(F01-1655-01)

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Page 2

KAC-819

CIRCUIT DESCRIPTION

SP P-CON Switching Circuit

When the SP output from the head unit is connected to SP IN, the power can be switched ON/OFF based on the
DC voltage of the SP output. However, As certain haed unit models output DC permanently or generate a click
during switching OFF, it is required to provide the capability of previous P-CON switching. A circuit which can
perform the switching without using a switch is described below.

This circuit performs switching by inhibiting the operation of the S-P»CON circuit when a voltage is applied to the
P-CON pin.

Circuit operation description

When the head unit is connected to SP-IN, the DC component in the SP output turns 038 ON through D32 and
R158.

When a voltage is applied to the P-CON pin under this condition, 045 is turned ON via R188. positive feedback is
applied by combination of Q45 and Q46, Q45 and 046 are held at ON, so the voltage at point (A) is almost 0V and
the SP-P-CON circuit is not activated.

This circuit holds the ON status while the DC voltage from SP is present.

Therefore, in this condition, the P-CON circuit continues functioning. To cancel the functioning, the voltage at the
SP-IN pin should go 0V.

D29
7.5V
to P-CON terminal 11¢ Power 00"0'
D32 R158 Q38
from SP-P-CON l>l - r
g f. 4.7K x
3 i. (7
no 0 1 0':
no ,-
E m
045
TUNER
INPUT OUTPUT ALIGNMENT
No. ITEM (RECEIVER) ALIGN FOR FIG.
SETTINGS SETTINGS SETTINGS POINTS
Connect a cassette receiver or other receiver.
IDEL Connect a DC . After sufficient aging
1 CURRENT ' voltmeter t0 0N3 VOIUme ' 0 VH3 adjust to 2mV '