Pioneer GEX-P7000TVP, Service Manual

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58
GEX-P7000TV,P7000TVP
7.2 CIRCUIT DESCRIPTION
- Multi-SIF
GEX-P7000TVP/EW and /ES adopt the multi-Sound IF method in order to support overseas TV broadcasting methods.
/EW and /ES are compatible with broadcasting methods B, G, H, D, K and I.
The frequency difference between the video and sound carriers is 5.5 MHz for broadcasting methods B, G and H,
6 MHz for I or
6.5 MHz for D and K.
In order to simplify the receiver configuration, the circuit is configured to control the local oscillator so that the video IF
turns 38.9 MHz.
When the video IF is 38.9 MHz, the sound IF turns 33.4 MHz for methods B, G and H,
32.9 MHz for I or
32.4 MHz for D and K.
Although video demodulation is now possible with a fixed frequency of 38.9 MHz, detection with the above settings is
uneconomical since the frequencies of the sound IF differ between each method as shown above.
By square-law-detecting the video IF of 38.9 MHz, the video signal returns to the base band signal and the sound IF
turns as follows:
B, G and H: 33.4 MHz
→
5.5 MHz
I: 32.9 MHz
→
6 MHz
D and K: 32.4 MHz
→
6.5 MHz
As shown above, the sound IF is converted into 5.5 MHz, 6 MHz or 6.5 MHz.
5.5MHz
VIDEO CARRIER SOUND CARRIER
SOUND IF (1st)
SOUND IF (2nd)
VIDEO IF
33.4MHz
38.9MHz
87.15MHz
48.25MHz
53.75MHz
5.5MHz
RF
Local
OSC
IF
VIDEO
detection
33.4MHz 38.9MHz
Freqency
Freqency
Freqency
Freqency
5.5MHz
EX.) CCIR 2ch method B receiving