1-2. H V Voltage Circuit
H V generator circuit (Fig 1-2-l)
H V generator circuit is composed on Q515, C530, C531, and FBT T503.
This circuit generates the flyback pulse. This pulse level is 450-55OVp-p.
This flyback pulse is boosted up to the high voltage (24 KV) by FBT.
The High voltage is supplied to the anode of CRT from FBT.
H V drive circuit (Fig l-2-2)
This circuit generates the drive pulse for FET Q515 in H V generator circuit.
The input of IC501 (pin
is supplied a trigger pulse from T502 of H deflection circuit.
IC501 outputs the drive pulse of FET Q515, and Toff (See Fig l-2-3) of IC501 output pulse is decided 10µS by
R530 and C528.
The output pulse of IC501 is supplied through emitter follower Q553, AC coupling capacitor C529 and buffer amp of
Q513, and Q514 to FET Q515.
H V generator or DC/DC converter circuit (Fig 1-2-l)
This DC/DC converter circuit is composed of a step down chopper, FET drive and control circuit.
This chopper circuit is composed of L507, D518 and C539.
This circuit supplies DC voltage of 35-l 20V to FBT for H V regulation.
The relationship between output DC voltage of chopper circuit and horizontal frequency is shown in Fig l-2-6
The FET drive circuit is composed of the buffer circuit of Q520, 0521, R571 and level shift circuit of R544, C537,
R545, R582, D517,ZD507.
The DC level of the output pulse from the control circuit (pin
of IC5A4) is shifted and is supplied to FET Q517 by
this circuit. (See Fig l-2-4)
This control voltage is a negative feedback circuit and supplies PWM (Pulse Width Modulation) pulse through FET
drive circuit to FET Q517.
High voltage output is divided by resistors of R549, R5E2, R5E3, and 450M ohm resistor in FBT.
This divided voltage is supplied to the buffer amp and to the error amp.
The output voltage of the error amp is supplied to PWM circuit of IC5A4 and IC5A4 supplies PWM pulse through
FET drive circuit to FET Q517.
40
Summary of Contents for JC-1531 VMA-2
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