Sony TVP-08, Training Manual

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95
HV Drive
Overview
The HV drive circuit amplifies the H Drive signal and applies it to the HV
Output. It also uses the signal from the HV Regulation circuit to control
the peak drive to the HV Output.
HV Drive
The H Drive signal is input through CN8003/1 and looped through to
CN8003/2. If this connector is removed, the High Voltage section will not
operate. The signal is then input to Q8005/B through R8010 and R8011.
Notice that there is an input from the HV Stop 1 and 2 circuits here. In the
event of a protect scenario, this line would be pulled to ground and HV
Drive would be disabled. Q8005 is a buffer and the drive signal is output
from its emitter.
The signal is then wave shaped by R8008, R8015, C8007, C8006, R8003
and C8004. This signal is input to Q8003/B amplified and output Q8003/
C. This signal is coupled through T8001 HDT to the HV Out transistor.
Peak Drive
The peak drive of the HV Drive signal, which was output, from Q8003/C is
controlled by a signal from the HV Regulation circuit. The HV Regulation
circuit inputs a PWM signal to R8024. R8024 and C8010 integrate this
signal into a triangle wave. This triangle wave is input to Q8001/B. Q8001/
C outputs a smoothed triangle riding on a DC level. This signal is used to
control the conduction of Q8002.
Normally using +135 through the resistance of R8005 and R8007 would
develop the HV DRIVE signal. When Q8002 conducts it causes the HV
Drive signal to be developed through R8004 and Q8002 C-E junction.
This resistance is lower than that between R8004 and R8002, therefore a
larger peak signal can be output at Q8003/C.
Q8003/B
2V 20us
Q8003/C
20V 20us
Q8001/B
1V 20us