Erbe ICC 200, Service Manual

Page: 145 / 266

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3 CIRCUIT DESCRIPTION
Art. No.: 801
16-201
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9
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4
Voltage regulation for +5 volts
A controlled voltage of +5 volts is mainly required to operate the CPU, the TTL logic modules and the light
displays on the front panel. Since the capacity of this voltage source is relatively high, a switched-mode
power supply unit was used.
The circuit corresponds extensively to that of the +24 volt regulator: The instable input voltage is stabilized
to +5 volts by means of the regulator IC6. The proper presence of the output voltage is indicated by the
LED3.
From Pin 3 of the integrated switching controller IC1 of the +15 volt voltage regulation, a connection leads
to the transistor T2 of the +5 volt control. In this way it is possible to block the function of the +5 volt power
supply unit as long as the +15 volt supply is not available. This measure is used to increase the functional
security of the unit.
Tone generators for the signal tones
The tone generators are used to audibly signal all operating and danger conditions when operating the
surgical unit. To do this, three tone generators are available, the signals of which may be mixed with one
another to produce pleasant and differing tones in this way.
The timer IC4 produces the tone frequency for the first tone, which can be adjusted using the trim
potentiometer TP2 at 493 Hz.
Timer IC5 produces the tone frequency for the second tone, which can be adjusted using the trim
potentiometer TP3 at 414 Hz.
Timer IC7 produces the tone frequency for the third tone, which can be adjusted using the trim potentiometer
TP4 at 329 Hz.
The generated tone frequencies can now be switched on selectively using the analog switches on the IC8
and mixed with one another. The combination of individual tones is prescribed by the program and is
selected using the D-flipflops of the IC9 as a target memory and switched through using the analog switches
of the IC8. Via resistors R5, R7, R9, R24, R10 and R16, the tone frequencies are combined so that one
sound can result from several individual frequencies.
The volume of the operating tones can be adjusted using a potentiometer which is connected in parallel to
resistor R11.
The volume of the alarms must not be reduced. For this reason, the reduction of amplitudes by means of the
integrated analog switch IC8, Pin 10-11, which is also controlled by the CPU, can be passed by so that the
tone signal in this case is reproduced with the maximum amplitude at the tone output amplifier IC 2.
The R37, C9, C10, C11, R39 network is used for sound shaping, so that a pleasant sound results in the
loudspeaker which follows the tone amplifier.
Low voltage supply
Slot J2