Autosync Deflection Controller--Tda4857; X-Ray Protection & Afc(Auto Frequency Control) - Acer V551 Service Manual

Acer V551 (new) CRT Monitor Service Guide

(2) Autosync Deflection Controller--TDA4857

2.1 pin 1 is AFC feedback .
2.2 pin XRAY: if V XRAY > threshold (6.25V typical) switches the whole IC into protection mode.
2.3 pin 3,4,5,6,8 for B+ control function block.
2.4 pin 11(EWDRV) is a parabolic waveform used for pincushion correction
2.5 pin 16 generates video claming & blanking pulse.
2.6 pin 18,19 is I2C data.
2.7 pin 21 V-regulation.
2.8 the resistor from pin 28 (HREF) to ground determines the maximum oscillator frequency.
2.9 the resistor from pin 27 (HBUF) to pin 28 defines the frequency range.
2.10 pin 31 H-regulation.
2.11 pin 32 focus.
(3) X-ray protection & AFC(Auto Frequency Control)
(a) AFC in other words is HFLB (Horizontal Flyback) IC201 pin1, its for synchronize the
second stage (horizontal deflection) with first stage (input signal H-sync.).
(b) TDA4858 pin2 sense the voltage separated by R217, R218 and R219 from FBT pin9 40V. The
TDA 4857 pin2 trigger voltage is 6.14V. When the FBT pin9 40V increase to let the R219
voltage drop achieve 6.14V, the TDA4857 will shutdown. In the time H.V.=28.5KV.
161514131211
CLBL
HSYNC VSYNC VOUT1 VOUT2 EWDRV
ASCOR VSMOD
VAGC
HUNLOCK
SCL SDA
17 18 19 20 21 22
9 8 7 6
10
VCC DGND
HDRY PGND BDRV
IC201
TDA4857
VREF VCAP SGND HBUF HREF H CAP
HPLL1
23 24 25 26 27
Confidence and Property
Chapter 2 Circuit Operation Theory
5 4 3 2 1
BIN BOP
XRAY HFLB
BSENS
R220
2.7K
HPLL2 HSMOD FOCUS
28 29 30 31 32
TP3 TP4
C205 R217 R218
+
R219
47U 120K 51K
23.2K
25V (1%) (1%)
(1%)
(EL)
R222
27K
1/4W
+40V
HFLB
AFC
3