Ha, Hb And Hc Boards; Hd Board - Sony TRINITRON BVM-D9H1U Maintenance Manual

pull up the Ik detection terminal to 12 V in order to
prevent the protector circuit from erroneous operation.
The operating point of the Ik protector is ABL current =
630 µA.
. HV +B OCP Protector
The HV +B OCP protector is the circuit that holds down
the high voltage when the current flowing through the
DC. IN line exceeds the set value due to any abnormality
or trouble.
The DC IN line voltage is voltage-divided by the
resistors R1522 to R1524 that is sent to Q512 emitter.
The Q512 base receives the following voltage.
Vb (Q512) = DC. IN _ R568 x 1 (DC. IN) _ Vf (D536)
When the relation of Ve_Vb ≥= Vbe (Q512) is estab-
lished, Q512 turns on so that the protector output
terminal is latched to the "L" level by the circuit of Q516
and Q519. D536 is inserted in order to cancel the
temperature characteristics of the Vbe voltage. The
operating point of the HV +B OCP protector is I current
(DC. IN) = about 2.4 [A].
. HV +B OVP Protector
The HV +B OVP protector is the circuit that holds down
the high voltage when the HV +B line voltage exceeds
the set value or when HV voltage abnormally decreases
due to any abnormality or trouble.
The HV +B line voltage is voltage-divided by the
resistors R1514 and R1513 to activate the protector. The
operating point of the HV +B OVP protector is about
120 [V]. On the other hand, the detected output of the
high voltage of the FBT is compared with the voltage
level that is voltage-divided by R1532 and R1533 so that
the abnormally low voltage from the FBT high voltage
output can be detected in such a case of FBT layer short,
and the protector is activated in such an error. However,
this protector has a longer time constant that prevents the
protector circuit from erroneous operation. The operat-
ing point of this protector is HV voltage ≤ 6 [kV].
. Degauss Circuit
The degauss circuit consists of the PWM controller
IC503, the high withstand voltage FET driver IC506, the
drive FET Q517 and the peripheral circuit.
When the main power is turned on or when the manual
degauss is turned on, the control signal "DEGAUSS
ON" that is sent to CN501 pin-8 is detected at its rise-up
edge that sets "L" to IC503 DTC and to start oscillating
the PWM output. (Length of the oscillating period is
determined by the time constant of R518, R519 and
6-8
C518.) The signal that is output from IC503 pins-9 and -
10 is sent to IC506 pins-10 and -12 to generate the signal
that drives the FET in the subsequent circuit. The FET
gate receives the signal that repeats High and Low only
during the period when the PWM output is oscillating so
that the FET is turned on and off repeatedly. When the
FET is turned on, a current flows from the 120 V line to
the degauss line so that the CRT is degaussed.
. Heater circuit
The heater circuit consists of the DC-DC converter
IC510 and the peripheral circuit. The voltage that is
obtained by rectifying the pin-8 "H1" using the FBT pin-
7 output "H2" as the reference, is used as the power
supply of IC510. The voltage that is obtained by
rectifying the IC output with D530 and L505, is voltage-
divided by resistors. The voltage that is obtained by the
resistor-division is returned to IC510 as the feedback.
The heater circuit uses the step-down converter circuit as
its circuit configuration. The heater voltage that is
applied to CRT is 4.5 Vrms.

6-7. HA, HB and HC boards

Key scan and turning on and off the LEDs
The SUB CPU (IC on the HC board) sends out the LED on
signal and the key scan output signal using the serial signal
(MISO, MOSI, SCLK). It receives the key scan input
signal.

6-8. HD board

An input signal is selected from the various input signals
that are connected to the AUDIO INPUT connectors (1, 2
and 3). It amplifies the selected audio signal and outputs
the audio signal to speakers.
BVM-D9H1U/D9H5U/D9H1E/D9H5E/D9H1A/D9H5A