Socket Board (Avb421); Control Board (Avb451); Front Control (Avb431) - Hitachi EUB-5500 Technical Manual

6.4.4.3 NTSC/PAL signal detection circuit
Converts frequency of NTSC (fv: 60Hz) and PAL (fv: 50Hz) to voltage by the F/V converter
(IC301), and compares the voltage by the comparator (IC302) to output switchover
signals.
6.4.4.4 Degauss control circuit
The degauss switch is a momentary type.
about 10 seconds. It needs not to press continuously.
Also, when turning ON the power, degaussing is automatically effected.
6.4.5

Socket board (AVB421)

This board is mounted with CRT socket and supplies image signal, heater voltage, 1st and
2nd grid voltage and focus voltage to CRT.
6.4.6

Control board (AVB451)

Depending on each timing switchover signal, adjustment variable resistors are switched
over as shown in Table below.
Once it is set, images of respective timing can be displayed without readjustment.
Name Name Name Name
HEIGHT
H-PHASE
V-CENT
6.4.7

Front control (AVB431)

The front control includes the brightness and contrast variable resistors.
The brightness variable resistor adjusts brightness of raster, while the contrast variable
resistor adjusts brightness of image.
Either variable resistor is provided with the center click to obtain standard brightness when
centered.
Timing Timing
Timing Timing
640 640× × × × 480 480 800× × × × 600 800 600
640 640 480 480 800 800 600 600
VR21 VR20
VR17 VR16
VR13 VR12
6 - 8
Once it is pressed, degaussing is kept for
NTSC NTSC PAL PAL
NTSC NTSC PAL PAL
VR19 VR18
VR15 VR14
VR11 VR10
L1E-EA0229