Service manual

CA-17
Deflection Control
Introduction
After deflection control signals are produced by ICX2200, they need to be modified and amplified before
they are output to the deflection yoke. The CA chassis accomplishes this necessity for 25 to 36 television
sets through the sweep transformer and the surrounding horizontal and vertical deflection circuitry.
Horizontal Drive
The Horizontal Drive (H-Drive) circuitry exists to control the drive signal to the Horizontal Output Transistor
(HOT) as well as provide deflection to the horizontal yoke. Typically H-Drive operates at 15.734 kHz. As
it passes through the driver circuit, H-Drive signal is amplified to provide a sufficient signal to the HOT
without causing it to go into saturation, thereby preventing distortion of the drive signal. H-Drive is pro-
duced at pin 32 of the Video processor (ICX2200) and is passed to the drive circuit through R2227M, a
surface mounted resistor. The signal enters the base of Q3201 which is directly coupled through its emitter
to Q3202. Finally, the signal passes from the collector of Q3202 to the Horizontal Driver Transformer,
TX3205, where voltage-to-current conversion and proper waveshaping occurs.
1
3 4
5
6
TX3205
C3206
QX3203
LX3202
CX3212
C3204
Q3202
C3203
R3205
R3204
CX3205
RX3207
+18 VSW
R3203
C3202
Q3201
C3201
R3202M
R3201M
H-Drive from
Pin 32, ICX2200
Flyback Line to
Pin 30, ICX2200
H-Output to
Flyback & Yoke
<<Figure CA-15>>
Flyback Transformer
From here, the signal switches the HOT (QX3203) on to provide a current shunt for the sweep transformer,
TX3204 and the horizontal yoke. This switching alternately passes then blocks the B+ voltage provided
through the primary winding of TX3204 to the collector of the HOT. The changing magnetic field in the
sweep transformer caused by this action generates the high voltage (HV). This high voltage should normally
be between 26 and 30 kV. The particular value will correspond to the size of picture tube in the set. G2
(screen control) and Focus voltages are tapped from a portion of the same winding that HV is derived from.
As usual G2 and Focus may be adjusted by pots on the sweep transformer. These run to the CRT socket
board.