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Technology of Q 2500 colour TV set
This reset reaches MSP 3410 /pin 21, and the
two VCP 3230/33 /pin 15.
All other IC's either do not need a reset or
generate it on switching on the operating volt-
age.
4.1.5 Creation of cycle frequency
The internal oscillator of SDA 6000 is syn-
chronised with a 6 MHz quarz on pins 108 and
109. The cycle frequency for the bus systems
is obtained from this frequency by internal
distribution. They are from 70 to 400 kHz re-
spectively for the I²C bus systems. The cycle
frequency is transferred under software con-
trol depending on the current function.
4.1.6
Operational commands
The SDA 6000 receives operational com-
mands as serial data information by RSIG
signal on pin 9.
The local operating com-
mands are applied to the CCU on pin 126 as
various voltage values.
Pin 126 operates as an ADC with 6 bit resolu-
tion. By various voltage dividers on the three
operating unit buttons, various voltage levels
are produced.
The voltage levels are digitised by the ADC,
and based on the measured values the CCU
issues the appropriate commands.
The following voltages are produced by ma-
nipulation of the various buttons:
•
• "+" button
• "-" button
• " " button
The overtravel contact is connected to pin 93
of the CCU.
Document Q 2500
- 0.5 V
- 1.1 V
- 1.8V
68
4.1.7
LED display
The red standby LED is controlled via pin 96
of the CCU. In operation the remote control
commands in RC5 code are acknowledged by
transient illumination of the LED. For standby
operation the pin is set to the H level and
transistor Q 2853 thereby conducts, where-
upon the LED illuminates. The ON LED is
controlled via pin 78 with the ON/OFF-
command. When the power supply is switched
on this line is set to the L level, whereby the
green ON LED also illuminates. SAT standby
operation is indicated by illumination of the
two LED's.
4.1.8
ON/OFF function
If a switch-on command is present, the output
ON/OFF, pin 78 of the CCU is set to L level.
This blocks transistor Q 8111 in the standby
power supply, whereupon Q 8114 conducts
and attracts the relay. The system voltage is
able to reach the main power supply, which
begins to operate.
The device starts operating at the selected
program location. The output is once again set
to H level by an off command.
With an ON/OFF command the two transistors
Q 2961 and Q 2966, which form part of the
mute circuit, are switched, thus suppressing
input and output noises.
4.1.9
Protective circuit
In order to avoid excessive high voltage, c.r.t.
defects or other serious damage due to faults
in the vertical deflection, caused by excessive
beam current, the device is switched to
standby. In addition, pin 94 of the CCU is set
to H level. In normal operation L level is pre-
sent (see description basic board Section 5.2
– 6.2).
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