Horizontal Drive / H Pincushion Correction / Filament Voltage; Basic Horizontal Drive Circuit; Pmw Circuit - Sony KV-32XBR400 Training Manual

Horizontal Drive / H Pincushion Correc-
tion / Filament Voltage
Overview
The purpose of the horizontal drive circuit is to manufacture a magnetic
field that is used to sweep the CRT's electron beam from left to right on
the screen. Within the basic horizontal drive circuit there is a PWM circuit
that supplies the Horizontal Output transistor with voltage and provides
horizontal pincushion correction. The horizontal drive circuit also makes
the CRT filament voltage.

Basic Horizontal Drive Circuit

This circuit is split between an oscillator on the A board and an output
stage on the D board. The 33.75kHz horizontal oscillator is in the Y/C
CRT Drive IC201. IC201 outputs a 2Vp-p rectangular waveform from pin
40 while there is B+ at pins 55 & 61 and the 2.7MHz X201 crystal is
running. The horizontal drive waveform is buffered by Q211 and enters
the D board.
On the D board, an N channel MOSFET driver and an output transistor
amplify the signal to provide sufficient current to drive the HOT T5001 and
the H DY deflection yoke.
At the output stage, the HOT T5001 has a secondary winding that pro-
vides filament voltage while its main winding provides +200V for the RGB
video output ICs. While the H DY yoke provides horizontal beam deflec-
tion (sweep), a voltage divider consisting of capacitors C5058-C5060 tap
off a sample of the H spike from the H Output Q5030/Collector to start the
HV converter stage. This AFC-PLS is also used in the convergence and
dynamic focus stages.
The waveforms of the horizontal drive stage show typical signal shapes.
The difference between this set and a conventional one is that the hori-
zontal frequency is 33.75kHz (ch 2), not 15.75kHz (ch 1). When compar-
ing the input sync (ch 1) to the horizontal oscillator (ch 2), notice that they
are not in phase. This is because the DRC circuit doubled the H fre-
37
quency, but the MID circuit stored the video and output the signal at a
new H freq. of 33.75kHz, independent of the source.
PM3394, FLUKE & PHILIPS
ch1
1
ch2
2
ch3
ch4
3
CH1!2.00 V~
CH2!2.00 V~
CH3!10.0 V~ STOP
4
CH4! 125 V= ALT MTB5.00us L=2
Horizontal Drive Signals
Channel Name
1 15.75kHz H signal
Input
2 33.75kHz osc output
3 H Driver input
4 Horiz Output
Time base = 5usec/div.
PWM Circuit
The PWM circuit has two functions. First it provides a regulated 102Vdc
output for the H Output transistor. Second it compensates for horizontal
pincushioning and keeps the picture straight at the sides.
No horiz
pincushion
correction
ch2p
Location Voltage
NTSC generator from the
generator
IC201/pin 40 2.2Vp-p
Q5028/gate 12Vp-p
Q5030/Collector 1kVp-p
Pix is
bowed
inward