Hitachi 46W500 Training page 31

DP-3X AUDIO VIDEO MUTE CIRCUIT EXPLANATION
FRONT AUDIO OUT HARD MUTE PATH:
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The high from Q527 is routed to DA06 the through the PPS4 connector pin 4. The high continues to the
base of QAA2. When this transistor turns on, it supplies a Lo to pin 11 of IAA1 and hard mutes the Au-
dio Out. (Note: This is not the same thing as the Mute selected from the customer's remote. This is con-
trolled by the Front Audio Control IC IA01 internally and functions in three states, No Mute = 100%,
1/2 Mute = 50% and Full Mute = 0%.
OUT TO HI-FI MUTE PATH: The high from the Mute Activation circuit is also routed to the anode of DA54
and then to the cathodes of DA51 and DA52 to the base of QA51, and QA54. When these transistor turns on,
they grounds the Right and Left audio for the Out to Hi-Fi audio output jacks.
FRONT AUDIO OUT MUTE: Labeled as V MUTE 1 (Microprocessor Pin 49)
V MUTE 1: The high from the Microprocessor pin 49 to I010 (in pin 3 at 3.3V and out pin 17 at 5V). This
High is sent to the following 4 circuits:
1. To the Front Audio Out Hard Mute circuit routed through DA06. (Described above)
2. The high is also routed through DA03 to the base of QA01, and QA02. When these transistor turns on,
they ground the audio going into the Audio Output IC IAA1 at the PPS4 connector. Right audio in pin 2
of the PPS4 connector to pin 4 of IAA1. Left audio in pin 3 of the PPS4 connector to pin 2 of IAA1.
3. CRT Mute: See CRT Mute Path explanation above.
4. Out to Hi-Fi Mute Path: The high from the Level shifter I007 pin 13 is routed to the anode of DA53
and then to the cathodes of DA51 and DA52 to the base of QA51, and QA54. When these transistor
turns on, they ground the audio going into the audio for Out to Hi-Fi audio output jacks.
A MUTE PATH: (Microprocessor Pin 71)
A MUTE: Also, the high from the Microprocessor pin 71 to I007 (in pin 7 at 3.3V and out pin 13 at 5V).
This High is sent to the following 3 circuits:
1. Front Audio signal mute: The high from the Level shifter I007 pin 13 is routed to the anode of DA04
and to the base of QA01, and QA02. When these transistor turns on, they ground the audio going into
the Audio Output IC IAA1 at the PPS4 connector. Right audio in pin 2 of the PPS4 connector to pin 4
of IAA1. Left audio in pin 3 of the PPS4 connector to pin 2 of IAA1.
2. Main Tuner U301 Mute: The high from the Level shifter I007 pin 13 is routed to pin 25 of the Main
Tuner U301. This high mutes the Audio and Video outputs from the Tuner.
3. Out to Hi-Fi Mute Path: The high from the Level shifter I007 pin 13 is routed to the anode of DA53
and then to the cathodes of DA51 and DA52 to the base of QA51, and QA54. When these transistor
turns on, they ground the audio going into the audio for Out to Hi-Fi audio output jacks.
REC MUTE PATH: (Microprocessor Pin 70)
Record Mute signal path. This pin is only used in the DP-36 chassis. It is routed through D405 to pin 38 of the
PST1 connector on the Terminal PWB. Here it is routed to DV02 and DV03 and then to the bases of QV08 and
QV09. When this line goes high, the Audio Left and Right is muted coming from the monitor outputs. The DP-
36 utilizes a Digital Tuner (ATSC). The ATSC tuner also outputs NTSC video and Audio which is routed to the
Monitor outputs for VCR recordings. When the ATSC tuner (Antenna C) changes channels, the audio is muted
briefly to avoid the unnecessary noise during switching.
Note too that the DP-36 does not utilize D406 like all the other chassis.
FRONT SPEAKER OFF: (IA01 Pin 17)
Front Speaker Off signal. The high from the Audio Control IC IA01 pin 17 goes to 2 circuits:
1. It goes to DA07 to the PPS4 connector pin 4. The high continues to the base of QAA2. When this tran-
sistor turns on, it supplies a Lo to pin 11 of IAA1 and hard mutes the Audio Out.
2. It goes through DA05 to the base of QA01, and QA02. When these transistor turns on, they ground the
audio going into the Audio Output IC IAA1 at the PPS4 connector. Right audio in pin 2 of the PPS4
connector to pin 4 of IAA1. Left audio in pin 3 of the PPS4 connector to pin 2 of IAA1.
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