JVC 370 SC, 330, 340 SC service manual CRTs, Output Description, High Voltage Power Supply

Chapter 2—Functional Descriptions

Table 2-11Video Amplifier Board I/O Signals

	Video Processor Board
Input	Description
VIN	COAX input from VPB via the backplane. Video signal of 1V peak-
	to-peak maximum.
/ENABLE	TTL level DC signal which controls grid voltages. High causes G2
	to be pulled to +15V and G1 to be pulled to -200V shutting off
	the CRT beam.
CLAMP	TTL level pulse controlling DC restore. Restores black level of
	cathode voltage to +84V.
BLANKING	TTL level signal controlling video blanking. Pulls G1 to 30V below
	normal voltage to turn off beam.

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
	opens when supply goes below 64V.

	CRTs
Output	Description
FOCUS	Focus voltage directly from HVPS to CRT.
GRID1	Regulated DC voltage to Grid1. Nominally -81V during normal
	operation. During blanking, G1 is -111V, and during /ENABLE
	high, G1 is -200V.
GRID2	Variable DC voltage to Grid2. G2 voltage is normally 800 to
	1200V. When /ENABLE high, G2 is 15V.
CATHODE	DC black level modulated by video signal. DC black level is +84V.
	Modulation is negative-going 75V peak-to-peak max.
FILAMENT	6.3V filtered goes to filament.
FILAMENT	Return from filament supply.
RTN

	High Voltage Power Supply
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
	circuit for protection.

2-58 Model 330. 340SC, and 370SC Service Manual