JVC 330 Service Manual page 70

Chapter 2—Functional Descriptions
Table 2-11 Video Amplifier Board I/O Signals
Input Description
VIN COAX input from VPB via the backplane. Video signal of 1V peak-
/ENABLE TTL level DC signal which controls grid voltages. High causes G2
CLAMP TTL level pulse controlling DC restore. Restores black level of
BLANKING TTL level signal controlling video blanking. Pulls G1 to 30V below
Outputs Description
BEAM Positive voltage indicating beam current averaged over several lines.
1mV = 1uA of beam current.
/VIDOK Indicates health of the +100V cathode supply. Open collector output
Output Description
FOCUS Focus voltage directly from HVPS to CRT.
GRID1 Regulated DC voltage to Grid1. Nominally -81V during normal
GRID2 Variable DC voltage to Grid2. G2 voltage is normally 800 to
CATHODE DC black level modulated by video signal. DC black level is +84V.
FILAMENT 6.3V filtered goes to filament.
FILAMENT Return from filament supply.
RTN
Inputs Description
-200V Power supply to Grid1 regulator.
FOCUS Pass-through from HVPS to CRT.
G2 +100V to +1400V supply to Grid2. Passes through G2 pulldown
2-58
Video Processor Board
to-peak maximum.
to be pulled to +15V and G1 to be pulled to -200V shutting off
the CRT beam.
cathode voltage to +84V.
normal voltage to turn off beam.
opens when supply goes below 64V.
CRTs
operation. During blanking, G1 is -111V, and during /ENABLE
high, G1 is -200V.
1200V. When /ENABLE high, G2 is 15V.
Modulation is negative-going 75V peak-to-peak max.
High Voltage Power Supply
circuit for protection.
Model 330. 340SC, and 370SC Service Manual