P Board - Sony TRINITRON BVM-D9H1U Maintenance Manual

choke coil that is inserted to raise the +B voltage during
15 kHz input mode. Q2519 is the switch to add the S-
shape capacitor for 15 k and 30 k to the circuit, and is
driven by Q2522 and Q2523. The control signal for
switching these horizontal frequencies is supplied from
IC2502 (D/A converter).
. . . . . Vertical Output Circuit
The vertical output circuit consists of IC2504 and its
peripheral circuit.
The vertical output signal is generated by inputting the
V. drive signal that is output form IC2503 pin-29, to
IC2504 pin-1 where it is amplified. The V. center
position is controlled by inputting the V. DC signal that
is supplied from IC2503 pin-28, to IC2504 pin-7. The
vertical deflection amplitude and the vertical center
position are controlled by IC2503.
The vertical feedback pulse is generated by wave-
shaping the V. flyback pulse with R3505, R3506 and
D2524, and by inputting it to IC IC2503 pin-30.
. . . . . H CENTER Circuit
The H CENTER control is performed by converting the
DC voltage level of IC2502 (D/A converter) pin-7 to
electric current by IC2518, Q2516, amplified by IC2507,
and by super-imposing an appropriate DC current upon
the horizontal deflection current through L2504 (HCC).
The power supply for IC2507 uses the floating power
supplies that are HC+, HC- and HC N as described
before.
. . . . . Protector Circuit
The D board (P2) has the three protectors that are H.
PROT, V. PROT and H+B OVP. The H. PROT is the
protector that is activated when the horizontal deflection
is stopped. It detects existence of the collector pulse
with IC2514, IC2515, D2519 and C576 after the collec-
tor pulse is divided by C2556 and C2557.
V. PROT is the protector that is activated when the
vertical deflection is stopped. It detects existence of the
V. out waveform after the V. out waveform is rectified
and smoothed out by D2523 and C2578.
H+B OVP is the protector that is activated when the + B
power voltage has increased by some defects. It detects
the + B voltage after it is divided by R2552 and R2553.
Operating point of the protector is about 65 V.
6-6

6-6. P Board

The P board consists of the PWM circuit for horizontal
deflection system and for high voltage system, the + B
power supply for high voltage output, protector circuit,
degauss circuit and heater circuit.
1. PWM Circuit for Horizontal Deflection and
High Voltage Systems
The PWM circuit for horizontal deflection system has
already been described. The PWM circuit for high voltage
system controls length of the ON period of the high
voltage PWM output that is output from IC504 pin-13.
The ON period is controlled by the error output that is
obtained by comparing the reference voltage that is
generated by the shunt regulator IC504 with the high
voltage detected output that is output from FBT pin-12
which is the voltage obtained by dividing the high voltage
(HV) with resistors.
For your reference, the input signal that is used as the
reference of horizontal defection and the high voltage
systems is the HD signal that is output from IC2503 pin-
21. The HD signal is locked to the input signal of the
monitor. (When there is no input signal to the monitor, it
synchronized with the free-run frequency.)
There can be a case that the horizontal output circuit and
the high voltage output circuit are damaged because they
cannot follow the sharp change of input frequency when
frequency of the input signal is changed or when input
channel is switched. In order to prevent the horizontal
output circuit and the high voltage output circuit from
damage, IC502 reduces the ON period of the horizontal
and high voltage PWM output to their minimum (by
decreasing the + B voltage so that the horizontal deflection
size is reduced to minimum and high voltage is decreased
to the lowest voltage) when IC502 receives the frequency
change information from IC2503 pin-37 (DTC: Dead Time
Control) in the D board. The ON period is controlled until
these circuits are locked o the input frequency slowly with
some time constant in order to prevent these circuits from
damage.
IC502 also has the built-in HD drive output circuit that
receives the HD input signal and is locked to the input HD
frequency. Phase and ON time of the HD output signal is
determined by the voltages that are applied to pin-22 and
pin-21 respectively. In this monitor, this HD drive signal
is also used as the drive signal of te high voltage output
circuit.
BVM-D9H1U/D9H5U/D9H1E/D9H5E/D9H1A/D9H5A