ADJUSTMENT
KAC-719
2
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 head 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-INN, the DC component in the SP output
turns Q38 ON through D32 and R158.
When a voltage is applied to the P-CON pin under this condition, Q45 is
turned ON via R188, positive feedback is applied by combination of Q45 and
Q46, Q45 and Q46 are held at ON, so the voltage at point (A) is almost 0 V
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 0 V.
Q46
4.7k
R158
to P-CON terminal
from SP-P-CON
D32
R188
100k
10u 35
3.3k
Q45
A
Q38
power control
D29
7.5v
No
ITEM
INPUT
SETTINGS
OUTPUT
SETTINGS
TUNER
(RECEIVER)
SETTINGS
ALIGNMENT
POINTS
ALIGN FOR
FIG.
Connect a cassette receiver or other receiver.
1
IDLE
CURRENT
–
Connect a DC
voltmeter to CN3
Volume : 0
VR3
After sufficient aging
adjust to 2mV
(a)
