25/08/2004 ©
Söring
Service-Manual Arco- and RF-units
1
not valid for A-3000/ -2000
2
not valid for Arco-2000
-38-
3
not valid for MBC600
4
not valid for Arco-1000
7. Description of RF-output module
7.1. General description
The RF-out module transfers the RF-signal of the cut- and coagulator module to the
handpieces and monitors the delivered RF-power. It consists of the two boards HFO_A
and HFO_B. The first board (HFO_A) contains the output transformers necessary for the
supply of monopolar and bipolar handpieces, the relays needed for allocation of radio-
frequency and the measuring transformers for power measurement and PE-electrode
contact check. By means of another relay the RF-current can be switched to a measuring
resistor for checking of the cut- and coagulator module. This allows testing of the RF-
modules and the RF-power measurement by the self test after switching on the
equipment.
The second board (HFO_B) contains the I
2
C-interfaces for relay control and the
necessary analog multipliers and DACs for power measurement etc. In order to check
these analog interfaces, they can be tested mutually with different reference voltages.
The design of the patient circuits complies with the CF-standard (PE-electrode potential
free, i.e. without capacitive grounding).
7.2. Description of board HFO_A
The board HFO_A is the main board of the module. It contains all allocation relays for
modules, handpieces and the power test resistor. Furthermore it contains the two output
transformers (bipolar and monopolar) and the measuring transformers for power
measurement and PE-electrode check.
The board gets the RF-signals from the cut- respectively Coagulator module and
transfers the RF alternatively to the two monopolar outputs or the bipolar output. For
testing the output power measurement and the RF-modules the output signal of the
modules can be switched to a test resistor. The power supply (
±
15V) for the relays and
the piggy-back board is made via this board.
7.2.1. Design/function of board HFO_A
The radio-frequency from the cut- or coag-module enters the board via socket J1. Relay
REL1 selects cutting or coagulation. REL2 switches RF to an external resistor of 4.7
Ω
for
testing of the power measurement. The capacitors C1 to C4 simulate the patient safety
capacitors. This is necessary for the correct function of the RF-modules with this test.
The insertion of the test resistor before the output transformers is advantageous,
because on the secondary side high voltage strength would be required. For safety
reasons the idle position of REL2 (without voltage) always switches the RF to the test
resistor. The relays REL3 and REL4 switch the RF to the monopolar respectively bipolar
output. In idle position these relays switch the output transformers to tissue impedance
test, signals MON_TST and BIP_TST. A circuit on the piggy-back board (HFO_B) can
test the loop impedance between active and PE-electrode. The secondary of the bipolar
transformer TR4 is connected to the tweezers via the two patient safety capacitors and
socket J3. After the monopolar patient safety capacitors C5 and C6 the two handpiece
allocation relays REL5 and REL6 are located. These relays connect the output
alternatively to one of the handpieces. The relays are high voltage types.
In order to locate errors in handpiece allocation due to faulty relays (burnt contacts,
wrong relay control), driver or software, the additional high voltage relays REL7 and
REL8 are provided. By appropriate opening and closing of these relays with a
simultaneous measurement of the loop impedance a complete test of these relays can be
performed.
With closed relays REL5 and REL7 respectively REL6 and REL8 a capacitance check of
the patient safety capacitors during self test is also possible. The RF flows back from the
two patient electrode halves via the patient safety capacitors C7 and C8 and the
To Next Page
