Erbe ICC 200, Service Manual

Page: 163 / 266

163
/ 266
3 CIRCUIT DESCRIPTION
Art. No.: 801
16-201
0
9
/ 200
4
The following assemblies are located on the PCB:
• Fingerswitch monitor 1
• Fingerswitch monitor 2
• Relays and their actuation for optional, separate connection of high-frequency to the required output
sockets.
The fingerswitch monitors are used to activate the surgical unit from the surgeon's handle. The monitor can
detect which output sockets carry high frequency and which current quality (cutting or coagulating) should
be switched on.
Since the handles are within the patient current circuit electrically, the monitor circuits must be designed
isolated from the unit circuit and from the chassis.
The monitor circuits must therefore be supplied with current from a floating voltage source. These voltage
sources must however also be well isolated at high frequencies, such as are used in high-frequency surgery.
This means that monitors with their voltage sources must be designed as low capacity compared to the rest
of the unit.
The voltage supply for the monitors is realized by two push-pull converters.
The voltage converter for monitor 1 essentially consists of the transistors T1, T2 and the transformer UE 1.
The voltage converter for monitor 2 essentially consists of the transistors T5, T6 and the transformer UE 2.
The transistors of this converter are monitored via the oscillator IC 6, which supplies a symmetrical, square-
wave signal, that is shortened in the monoflop IC5, in such a way that it is ensured that the two transistors
of a converter are not switched on at the same time.
The NAND circuits of the IC 4 create an appropriate push-pull signal that is directly suitable for actuation
of the converter transistors.
Since both fingerswitch monitors have identical circuits, the circuitry of only one of the two monitors is
explained in the following:
On the secondary side of the converter transformer UE 1, a needle-shaped output signal forms in the mid-
frequency range which is directed both to the diode bridge D1 to D5 with the transmitter diode from IC 1 as
well as via the RC low-pass C3, R2, C1, R1 on the handle's selection keys.
Due to the bridge circuit for diodes D1 to D5, the transmitter diode for optocoupler IC 1 may be illuminated
during both half-waves and connect through the receiving transistor for the optocoupler IC 1 by pulses.
If, on the other hand, a key on the handle is pressed, a voltage needle for the converter voltage is dampened
by the Si diode integrated into the handle, so that the transmitter diode for the coupler IC1 can no longer be
illuminated for the affected voltage needle and the appropriate transistor is no longer connected through at
exactly this voltage needle.
The output signal from the receiving transistor is directed to the two data inputs for the D-flipflops of the
IC3. These two D-flipflops additionally receive the actuation signals for the converter transistors, so that a
definite assignment is possible here between the dampened voltage needle and the actuation signal. The
two D-flipflops therefore function as a scanning circuit in proper phase, the output signal of which can be
assigned to the switched key in the handle.
Relay board
Slot J8 (for ICC 300, 350)