Hitachi 43FWX20B, Training

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DP-2X AUDIO VIDEO MUTE CIRCUIT EXPLANATION
PAGE 03-17
AUDIO MUTE PATH: Labeled as V MUTE 2:
See the Mute Activation circuit explained previously.
When Q441 collector is high, the base of Q440 is high. This turns it on and supplies a high from the emitter.
This high is routed to the following circuits;
OUT TO HI-FI MUTE PATH: Labeled as V MUTE 2:
The high from Q440 is routed to DA03 anode. Then DA01 , and DA02 fire and supply the high to the bases of
QA07
and
QA08
. These in turn ground out the audio for Out to Hi-Fi audio output jacks.
Also, the high from the Microprocessor pin 71 to I007 (in pin 7 at 3.3V and out pin 13 at 5V) to the anode of
DA04 causes the same results.
MONITOR MUTE PATH: Shown going to the Terminal PWB. Labeled as V MUTE 2:
The high from Q440 is routed to PST2 pin 9 . On the terminal board is an exact same circuit as describe in the
Out to Hi-Fi Mute Path above. So the actual circuit is not show here, just the description. The high from the
PST2
connector is then sent to the anode of
DX03
. Then to
DX01
, and
DX02
fire and supply the high to the
bases of QX01 and QX02 . These in turn ground out the audio to the Monitor Out jacks.
Also, the high from the Microprocessor pin 49 to I007 (in pin 3 at 3.3V and out pin 17 at 5V) to the same circuit.
CRT MUTE PATH: Shown going to the CRT PWB. Labeled as V MUTE 1:
The high from Q440 is routed to PSC pin 11 . This high goes to Q8C1 base. This turns on and supplies a ground
to the following diodes, D8A3 on the Blue CRT PWB, D853 on the Green CRT PWB, D803 on the Red CRT
PWB. When the diodes are supplied with a ground on their cathodes, they remove the base voltage fro the RGB
drivers,
Q8A3 , Q853 , and Q803 on the Blue, Green and Red CRT PWBs.
FRONT AUDIO OUT HARD MUTE PATH: Labeled as V MUTE 2:
The high from
Q440
is routed to
DA08
. The high continues to the base of
QA11
. When this transistor turns on, it
supplies a Lo to pin 11 of IA03 and hard mutes the Audio Out. (Note: This is not the same thing as the Mute se-
lected from the customer’s remote. This is supplied by the Front Audio Control IC and functions in three states,
No Mute = 100%, 1/2 Mute = 50% and Full Mute = 0%. Also, the high from the Microprocessor pin
49 to I007
(in pin 3 at 3.3V and out pin 17 at 5V) to the same circuit.
FRONT AUDIO OUT MUTE and A MUTE PATH: Labeled as V MUTE 2 and A MUTE:
The high from
Q440
is routed to
DA05
. The high continues to the base of
QA19,
and
QA10
.
When these transistor turns on, they in turn ground out the audio going into the Audio Output IC, Right audio in
pin
4 of IA03 , Left audio in pin 2 of IA03
A MUTE: Also, the high from the Microprocessor pin 71 to I007 (in pin 7 at 3.3V and out pin 13 at 5V) to the
anode of
DA06
and on to the same circuit.
Ft Spk Off: (Front Speaker Off) Also, the high from the Microprocessor pin 72 to the anode of DA07 and on to
the same circuit.