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3.5.S
High Voltage Circuits
CRT anode voltage is produced by rectification of a
horizontal retrace pulse obtained from the high voltage
winding of high voltage transformer, T59l(FBT).
High voltage remains independent of anode current in
order to maintain stable high voltage performance.
The rectangular waveform voltage, produced
by
comparator
IC502, is applied to the High
V~ltage
driver Q301.
Transistor Q301 drives interstage transformer T301,
which then couples the drive signal to the base of
High Voltage output transistor 0351.
The pulse at the collector of Q351 is stepped up by
high voltage transformer, T591 and rectified
by
high
voltage rectifiers located on T591.
The high voltage is then divided by resistors VR591
and R311, fed to the error amplifier Q303 through
buffer amplifier Q302.
The base voltage of Q303,
which is proportional to the high voltage, is compared
with Zener voltage of 0303.
This differential voltage
is amplified before driving the High Voltage regulator
Q304 and Q352.
If the differential amplifier does not maintain a
normal high voltage condition, the differential voltage
controls the emitter voltage of transistor Q352 through
Darlington transistor 0304.
3.5.6
High Voltage Safety Circuits
High voltage safety circuits are located on the PCB-
DEFL. (Refer to Fig.3-2)
If high voltage reaches to a certain designed level
above 29
KV,
protector circuits begins to operate
and cuts off high voltaae drive circuits.
3-15
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