Philips DVD 580M, Service Manual, Page: 51 / 60

Circuit description
EN 51 DVD580M 9.
betweenR231 and R244 will change the deep of echo effect,
the value of R241 will affect the delay time of voice.
This additional diagram will help to understand the structure of
PT2399 (chip set for karaoke feature).
Figure 9-19 Karaoke Chipset
PT 2399 is an echo / surround sound processor, both ADC and
DAC are build in side the chip set, which convert the analogue
voice from microphone into digital for time delay processing.
The Mute Circuit For Microphone Input
Figure 9-20 Microphone Mute Circuit
When the Microphone is turn off, MICMUTE voltage will drop to
0V from 3.3V. A +5V voltage will be divided to +2.5 V through
R126, R127 and force the Q17 to be conducted hence switch
on the Q 16 and Mute the Microphone input.
When service work is needed on Microphone part, press the
MIC button on the remote handset and measure the change of
MICMUTE voltage, which help to know if any defect on the
circuit.
Sound Muting When Switch On And Off The Set
Figure 9-21 Sound Muting
During the set is being ON and OFF, there will be POP noise
from the audio, which is caused by the voltage surge from
audio channel.
When the main is connected to the set, only VCC (+5V) is
available at the moment. Set will be turn ON if the power key
on the remote handset is pressed. POP noise appears during
the setup time of VA+ and VA-.
In order to suppress the POP noise, a PMUTE voltage has to
be providing to Q12 and make it turn OFF (Mute activation)
before the PCON arrive. On the other hand, Q13 circuit is used
to prevent the POP noise from mains shut down instead of
normal turn OFF.
Figure 9-22 PMUTE Timing Chart
Note that the time different between PMUTE and setup time of
+5V. PMUTE voltage is controlled by the U302 at the front
panel. If any poor audio outputs happen, check and make sure
the mute circuit is not faulty
Vfd Driving And Key Control Scanning
Figure 9-23 VFD Driver
To light up the VFD display, the heater filament of the VFD
(AC1, AC2), a negative voltage (-24V), grid terminal (G1 to G4)
to Anode voltage controlled by the driver chip set are provided.
DEM
4
LPF1-IN
7 13
+
-
0
+
-
0
OP2-IN
CLOCK
1/2Vcc
OP1-IN
6
11
CC0
10
CLK_0
5
+
-
0
reset
9
MI
OP1-OUT
DO1
LPF2
3
Auto
AGND REF
8 15
VCO
DO0
14
+
-
0
DI
12
LPF1
OP2-OUT
16
1
LPF1-OUT
2
MO
LPF2-IN
+
-
0
COMP
LPF2-OUT
DGND
CC1
VCO
MOD
VCC
CL 26532085_044.eps
190702
44kbits
RAM
Q17
9015C
R107
2.2K
5V
MIC1
R114
1k
R131
10K
R115
470R
Q16
2878
R126
2.2K
MICMUTE
CL 26532085_045.eps
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R109
10K
D3
1N4148
R106
100K
+
C130
470uF/16v
MUTE
VA 1
R104
100K
R108
1K
R105
10K
Q12
9015C R128
0R
Q13
9015C
R130
0R
PMUTE
D2
1N4148
CL 26532085_046.eps
190702
VCC
5V
PMUTE
+5V
500ms
CL 26532085_053.eps
180702
DEM
4
LPF1-IN
7 13
+
-
0
+
-
0
OP2-IN
CLOCK
1/2Vcc
OP1-IN
6
11
CC0
10
CLK_0
5
+
-
0
reset
9
MI
OP1-OUT
DO1
LPF2
3
Auto
AGND REF
8 15
VCO
DO0
14
+
-
0
DI
12
LPF1
OP2-OUT
16
1
LPF1-OUT
2
MO
LPF2-IN
+
-
0
COMP
LPF2-OUT
DGND
CC1
VCO
MOD
VCC
CL 26532085_044.eps
190702
44kbits
RAM