Mitsubishi Electric HITACHI VS-50111 Troubleshooting Manual page 37

V20 Chassis Technical Training
and Troubleshooting Guide
play format and no POP is activated.
When PIP is activated the sub picture
is inserted in the main picture in IC2Y01.
The YS signal from PCB-DOUBLER
times the insertion.
When the shape or size of the main pic-
ture is changed, due to a display format
change or POP activation, the main sig-
nal 480p and 1080i signals must be pro-
cessed in DOUBLER circuitry. In this
case, POP or PIP insertion occurs in
DOUBLER circuitry and the combined
signals are directed through IC2Y01 to
the VCJ.
The YCbCr circuitry in the VCJ en-
hances the YCbCr signals, improving
picture quality. The signals are then
converted to RGB and directed to their
respective CRTs.
CRT RGB Circuitry
Figure 4 shows the CRT's RGB Am-
plifier circuitry. Each CRT's respective
signal is amplified in an IC, either
IC6R01, IC6G01 or IC6B01, and ap-
plied to that CRT's cathode.
The output at pin 7 of the three RGB Amplifier ICs,
indicate the point at which that CRT starts to conduct.
The point of conduction for each CRT is checked dur-
ing the vertical blanking interval.
Three pulses in sequence are added to the signals in the
VCJ. The conduction point information for each CRT
is fed back to the VCJ. If the conduction point has
changed, the Cutoff Adjustment for that CRT is auto-
matically adjusted if necessary.
5-5