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DP-4X HORIZONTAL DRIVE CIRCUIT EXPLANATION
H Blk for HORIZONTAL DRIVE FOR THE HIGH VOLTAGE CIRCUIT:
•
The Horizontal Blanking signal H Blk from Q706 is also sent to the High Voltage Driver IC IH01 pin
(3). This IC uses this signal as a Tickle Pulse signal to lock the high voltage H. Drive signal from IH01
pin 1. The high voltage H. Drive signal is output pin 1 and routed to the driver transistors, QH02. Then
to the High Voltage Horizontal Output Transistor QH01. This transistor switches the primary of the Fly-
back transformer TH02. Deflection SW +115 is sent through pin (9) and output pin (10) to the collector
of the Horizontal Output Transistor QH01.
A sample of the High Voltage is output from the Flyback transformer TH02 pin (12). This voltage is sent to pin
(9) of the High Voltage Driver IC IH01. This voltage is compared to the reference voltage available at pin (12).
If there is a difference between the two voltages, an error voltage is generated and output from pin (10) and input
again at pin (11) where it manipulates the PWM (Pulse With Modulation) signal producing the Horizontal Drive
signal output from pin (1).
It's important to notice that the High Voltage circuit can not function without the Horizontal Deflection circuit
providing a drive signal. The Sweep Loss circuit will sense the loss of H. Blanking and output a high that's
routed through D719 to pin 3 and DH02 to pin 14. If these voltages go high, pin 3 will defeat the H. Drive by
saturating the internal op-amp that creates the sawtooth comparator signal. Thus stopping H. Drive. Pin 14 high
will saturate the internal generator that produces the sine wave for the sawtooth op-amp. See Figure 1 below.
GENERAL INFORMATION:
The DP-4X deflection circuit differs from analog Hitachi projection televisions. It utilizes in a sense, two hori-
zontal output circuits. One for Deflection and one for High Voltage. This allows for better deflection stabilization
and is not influenced by fluctuations of the High Voltage circuit which may cause unacceptable breathing and
side pulling of the deflection.
3
Gen
9
DC Feed Back
12
DC Ref.
Fig 1
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+
DC Ref.
+
-
+
-
1
10 11
PAGE 05-02
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