Kenwood KAC-X1R - eXcelon Amplifier, Service Manual

Page: 8 / 30

KAC-PS1D/X1R
8
CIRCUIT DESCRIPTION
0V
0V
D176
D174 D175
D173
D172
IC22(1/2)
(2/2)
IC22
RESONANCE DET.
TP33
TP5
TP103
3
2
1
8
5
4
6
7
3300P
C198
47K
R339
0.01
C200
0.033
C201
0.033
C202
1K
R346
1K
R347
2.2K
R345
3300P
C199
47K
R340
22K
R343
10K
R344
0.033 C203 0.022 C204
10K
R348
R341 47K
R342 47K
C207 0.01 C208 0.01
TP9 TP30
TP6 TP7
TP31 TP32
TP27
from SP+ OUTPUT
TERMINAL
from SP- OUTPUT
TERMINAL
to COMPARATOR
BPF
14.4V
4.9V
2.5V
13.4V
Q51
Q50
Q52
Q53
Q47 Q55
Q54
Q48
D48
D49
D46
TP289
1
R73
1
R80
1
R81
47u25
C47
2.2K
R79
4.7
R98
4.7
R97
4.7
R96
4.7
R95
4.7
R94
4.7
R88
4.7
R91
4.7
R92
4.7
R93
22K R99
4.7K R66
100
R87
R74 47 R72 47 R71 47
R90
4.7
4.7
R89
C46
47u25
TP337
+
+
IC7
Q174
Q187
Q186
Q176
Q177
Q178
D169
D171
D165
D164
Q184
Q185
TP383
TP385
TP384
R219
1.5K
TP105
TP104
6
5
7
8
V+
V-
3
4
2
1
10K
R291
10K
R287
10K
R286
0.01
C189
R292 10K
C183 0.01
1
R830
1
R820
1K
R257
C184 1000P
10K
R256
R225 62K
1K
R259
3.3K
R213
0.047 C172
10
R307
10
R304
33K
R226
3.3K
R223
5W
0.01
R204
0.047 C178
1.5K
R224
0.01
R203
5W
●
Short detection circuit between SP+ and SP- terminals
If the SP+ and SP- terminals are shorted in the vicinity of the
terminals, the self oscillation occurs in the D-class amplifier.
The oscillation in opposite phase is caused between the +
and - terminals of the BTL, and this oscillation is applied to the
differential amplifier, IC22 (2/2) to limit the amplitude with the
zener diodes such that the voltage does not exceed the with-
stand voltage.
The output from pin 7 of IC22 is rectified through the band
pass filter whose center frequency is about 3kHz.
The DC voltage generated after the rectification is applied to
the comparator, (IC6 (2/2)) and generates “L” at pin 7 of IC6
when the voltage exceeds the preset threshold.
●
Power supply circuit for FL
• V-FL
V-FL is the power supply for grid of FL. D48 is used to select
either the battery or +15V power supply that has higher volt-
age.
The power supply voltage is set to constant 13V in D49. The
power is turned ON/OFF with Q54 and is applied to FL driver.
• FIL+
Power is supplied by the battery and the voltage is set to 2.3V
in D49 so that it is applied to the filament of FL.
The power is turned ON/OFF in Q48 in response to the FL-
ON signal from the
µ
-com.
●
Ground fault detection circuit
When SP+ or SP- output terminal is shorted to the ground,
the current running in the +B power supply and that in the -B
power supply are unbalanced.
The current unbalance (
±
) is measured by R203 and R204
and the currents are mixed in R225.
When the currents become out of balance due to the above
shorting to the ground, the voltage is caused across R225.
When this voltage exceeds the threshold decided by R256
and R257, the “L” output is generated at pin 7 of IC7.
As a result, the over current protection operation is activated.