Horizontal Drive Circuit; Horizontal Deflection Output Circuit - NEC MultiSync FP1370 Service Manual

IMAGE

3) Horizontal Drive Circuit

The horizontal drive system uses what is generally referred to as a flyback system.
The horizontal drive pulse output from IC501 pin 25 switches Q555 on and off.
It is amplified by T551 and switches Q561 (the horizontal output transistor) on and off.
The voltage of C552 for horizontal drive is fixed at 15V.

4) Horizontal Deflection Output Circuit

It corrects the optimum horizontal linearity by using Linear-coil and S correction capacitor to change the
horizontal frequency mode. Horizontal frequency mode is shown in CPU CIRCUIT description section.
The Inductance of Linear-coil (T571) varies with horizontal frequency.
①Variable Linearity Coil (T571)
Horizontal circuit has variable linearity coil (T571) and control the character to optimum in all resolution.
The value of T571 is changed by current of control coil and ambient circuit. The current goes down at
the lower frequency and goes up at the higher frequency due to change the base voltage of Q571.
Base voltage is adjusted to optimum by H.LINEARITY1 and H.LINEARITY2 as following.
Q571
Base
②S-Correction Circuit
IC571 (I/O Expander) make the matrix of FH band, and it switches a FET array (MQ571).
*Matrix of FH band (Refer to Fig. 6-1)
C519 WAVE
CORNER
TOP BALANCE
CORNER
BTM BALANCE
MIN.
(Fig.2.8) Voltage at C519 and screen image
H.LINEARITY2
H.LINEARITY1
31KHz 60KHz
Horizontal Frequency
C519 WAVE
LEFT/RIGHT
TILT
OSM MENU
106KHz
8-11
IMAGE
MAX.