6-5
BVM-D9H1U/D9H5U/D9H1E/D9H5E/D9H1A/D9H5A
The deflection signal processor IC2503 has the built-in
protector for X-ray irradiation. When its pin-15 is raised
to 8 V or higher, the X-ray protection circuit starts
working to stop the horizontal and vertical outputs. The
X-ray protector circuit can be reset by turning off the
main power once then back on.
There can be a case that the monitor receives the non-
standard TV signal such as the output signal from VTR.
In order to reduce the skew effect on screen caused by
irregular timing of the input sync signal, the PLL circuit
inside the IC2503 is stopped using the PLL stop signal
that is output from IC2523 during the vertical blanking
period. This function is effective when the horizontal
frequency of the input signal is 15 kHz (480/60i, 575/50i
,etc.) Because this circuit produces an ill effect when the
standard TV signal is input, use or not-use of this circuit
can be selected from the on-screen menu.
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. BLK Signal Processing
The H. blanking circuit consists of IC2513, IC2521,
IC2506 and the peripheral circuit. The timing reference
signal for the horizontal blanking is the H. DF signal
(parabola waveform of horizontal cycle) that is output
from IC2503 pin-17. The start position of the horizontal
blanking period is determined by creating a pulse by
comparing the parabola waveform with a certain DC
level at IC2506, and by comparing the output pulse with
the waveform that is output form IC2503 pin-22 (H.
BLKG). IC2513 determines the end position of the
horizontal blanking.
The V. blanking circuit consists of IC2509, IC2522 and
the peripheral circuit. The start position of the V.
blanking is determined by the fall-down edge of the VD-
signal that is output from IC2503 pin-29. The end
position of the V. blanking is determined by IC2509.
The H/V blanking signal are controlled of its timing by
the control voltage that is output from IC2501 (D/A
converter).
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.+B Power Supply Circuit for Horizontal Output
The +B power supply circuit for horizontal output
consists of Q2509, L2503, D2505, C2542 and other
devices.
This circuit uses the step-up chopper circuit in order to
produce the + B power in which the DC. IN input
voltage is stepped up by switching. When Q2509 is
turned on, a current flows from drain to source of Q2509
through L2503. When Q2509 is turned off, a counter
electromotive force is generated across L2503 that
charges C2542 through D2505 and generates the +B
voltage. Relationship between DC. IN and +B voltage is
shown below.
V (+B) = DC. IN + V (L2503)
It means that the output voltage can be changed in
accordance with the amount of energy that is stored in
L2503. In the other words, the output voltage can be
controlled by controlling the ON time of Q2509.
The +B power for the horizontal deflection system is
controlled by the PWM IC IC502.
The H. size control DC voltage is super-imposed upon
the horizontal PIN distortion correction signal that is
output from IC2503 pin-31. The super-imposed signal is
compared with the signal that is fed back from the
horizontal output circuit. The error signal of the compar-
ator is the PWM control signal (H. PWM) that is output
from IC502 pin-11. The PWM control output signal is
amplified by Q2507 and Q2508, then is sent to Q2509
gate so that it drives Q2509.
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. Horizontal Output Circuit
The drive signal (HD) for the horizontal output signal is
output form IC2503 pin-21, amplified by Q2512, Q2513,
Q2535 and drives T2503 (HDT). The HD signal that is
current-amplified by HDT, drives Q2514 and generates
the collector pulse by the resonance of the horizontal
winding of DY, the S-shape capacitor C2562, C2563 and
C2564. The collector pulse generates the AGC pulse
having 5 Vp-p with C2556, C2557, C2558, IC2508 and
the peripheral circuit. The AGC pulse is sent to the
deflection system control IC (IC2503), signal system B
board, microprocessor control system MA board.
The horizontal deflection current that flows through the
DY is detected of its peak value as the voltage data by
T2502 and is sent to IC502 that is the horizontal deflec-
tion control PWM IC on the P board. For the linearity
compensation of the screen, the right half of a screen is
compensated by the S-shape capacitors (C2562 to
C2564) and the left half of a screen is compensated by
HLC (L2505, L2509). When the video signal having the
horizontal frequency of 45 kHz (33.75 kHz < Fh ≤ 45
kHz), compensation is applied by L2509 and C2562.
When the horizontal frequency of 30 kHz (15.75 kHz <
Fh ≤ 33.75 kHz), compensation is applied by L2509,
C2562 and C2563. When the horizontal frequency of 15
kHz (15.625 kHz ≤ Fh ≤ 15.75 kHz), the relay RY2501
is turned off by Q2521 and compensation is applied by
L2505, L2509, T2504 and C2562 to C2564. T2504 is a
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