Mts Decoding (Fe-Vrsosr) - Hitachi 36SDX88B Service Manual

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ACCELERATION
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VIDEO INPUT
PRIMARY DtFFERENTtATED
VOLTAGE WAVEFORM
SECONDARY DtFFERENTlATED
VOLTAGE WAVEFORM
AUXlLtARY DEFLECTtON COtL
CURRENT WAVEFORM
(EQUIVALENT) HORtZONTAL
SCANNtNG CURRENT
VELOCtTY MODULATION
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PERFORMED
VELOCtTY MODULATtON NOT PERFORMED
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CRT HORIZONTAL
SCANNtNG STROKE
Fig. 11.2 VM Signal Process
12. MTS Decodinq (FE-VRSOSR)
1) Block Diagram
See item 1 "Tuner" - MTS Decoding
2) Stereo Demodulation
The stereo LPF is used to remove the SAP (5fH) and telemetry (6.5fl-l). The resulting
signal is sent to the phase detector. The phase detector converts to a DC voltage and
filtered. The 8fH VCO is divided and produces two fl-i signal, one in phase with the pilot
signal and the other 90 degree out of phase.
The signal from the Stereo LPF is also sent to the pilot decoder which converts it to a
DC voltage and is stabilzed by internal circuit which is used to determine the ON I OFF
condition of the Stereo indicator. The Pilot Cancel cancels the pilot signal by adding
the stereo signal with matrix signal at the response level of the input pilot signal. The
pilot signal is also sent to the L-R signal and the L-R signal goes to the ST/SAP switch.
The L + R LPF consists of 2 traps tuned to fH and 24kHz to remove the L+R signal and
passed through a 75~s de-emphasis filter to the mode selector.
3) SAP Demodulation
Block
The composite audio signal is also applied to the SAP BPF (peaked to 5fH) to remove
the SAP signal. The output of the SAP BPF goes to the SAP Detector. It is full wave
rectified to DC voltage and smoothened by the internal circuit. When this DC voltage
reaches a certain level, SAP signal is detected.
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