Sony TVP-08 Training Manual page 105

Overview
The High Voltage Out circuit uses the H Drive signal to produce the heater,
+210 V, High Voltage, Focus Voltage and ABL output. This circuit is regu-
lated by Q8008 whose conduction is controlled by a PWM signal from the
HV Regulation circuit.
HV Out
The horizontal drive signal is coupled to Q8007 HV Out through T8001
HDT. As the H Drive signal is applied to Q8007/B, it turns on and allows
current to flow through its C-E junction. This is from the snubber filter
network consisting of C8003, C8009, D8003, R8012, R8016 and R8020
to the +135 volt line through T8003 FBT and T8002 LOT. When the H
Drive signal goes low, the magnetic fields developed by T8003 FBT and
T8002 LOT collapse and charge C8018. When the magnetic field is dis-
sipated, C8018 discharges through T8003 FBT and T8002 LOT. The
remainder of the current flows through D8007 and D8011 damper diodes
until the H Drive signal goes high again.
The voltages developed across the primary windings of T8003 FBT and
T8002 LOT are used to create different voltages on their secondary. T8002
Low Output Transformer uses the winding across pins 15 and 17 to de-
velop the Heater voltages used by the picture tube filaments. The pin 15
side of the winding is fused using circuit protector PS8001. This line also
contains two current limiting resistors, R8038 and R8039. The winding
between pins 11 and 15 are used to develop +210 volts for the video drive
ICs. The voltage at T8002/11 is rectified by D8014, filtered by C8025 and
through R8183.
The secondary voltages from T8003 FBT are high voltages delivered to
the High Voltage Block and Focus Block. The amount of current being
drawn by the High Voltage is monitored using the ABL line at T8003/11.
ABL is used in a number of places including the HV Stop circuits. The
voltage output by T8003/6 is representative of the level of the High Volt-
age. It is used by the Hold Down circuit in the HV Stop 2 section.
HV Out
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High Voltage Regulation
The High Voltage is regulated using a signal developed by the HV Regu-
lation PWM signal discussed later. This signal is applied to Q8008/G.
This input waveform causes current to flow through Q8008. This is used
to control the width of the pedestal at the bottom of the Q8007/C wave-
form showed below.
Q8007/B
Q8008/G
Q8007/C
Q8008/D