Erbe ICC 200, Service Manual

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3 CIRCUIT DESCRIPTION
J 15 free
J 16–J 20 grey
J 17–J 21 brown
J 18–J 22 yellow
J 19 free
In the 115 volt range, the bridge-connected rectifier BR1 operates with the electrolyte capacitors C6, C7 as
a voltage doubler. The wire bridges must be connected as follows:
J 15–J 20 grey
J 16 free
J 17 free
J 18–J 21 brown
J 19–J 22 yellow
For the low voltage supply, there is a transformer TR 1 with rectifier BR2 and filter capacitor C15 on the
motherboard. Here an unregulated DC voltage is provided in the 24 volt range.
Since data are present on the databus for all parts of the circuit simultaneously, it is necessary to separately
determine for which part of the circuit the currently output data is intended. This is realized by the “Chipselect
method” by which the chip to be addressed is selected and addressed using a special “Chipselect signal.”
This signal activates only one among a number of addressable modules. These signals are generated within
the Multiplexer IC 4 and converted in the transistor arrays IC10 and IC11 to 15 volt CMOS level.
The PIO (Parallel Input Output module) produces data in a brief period of time for many different target
assemblies. While the data are only present briefly at the PIOs, the data for target assemblies should be
present longer. For this an independent external control bus and independent control lines are used. The
data for the signal lines are stored in the D-flipflops IC2 and IC3 and brought to the 15 volt CMOS level in
the transistor arrays IC8 and IC9.
For the external control bus, the PIO data only need to be brought to the 15 volt CMOS level in IC7.
Limitation of the high frequency leakage currents
High frequency leakage currents are effectively limited in the ICC. The transformer UE1 is used for limitation.
All lines which lead to a high-frequency output socket on the ICC are directed via transformer UE1. If no
high frequency leakage currents occur, the HF current flows from the generator via the patient to the neutral
electrode and via the transformer UE1 back to the generator completely.
Therefore ideally, the current flowing away is equal to the current flowing back. The windings of the
transformer UE1 are switched in such a way that the resulting magnetic field is canceled by the current
flowing back and forth. Thus the windings of this transformer have no inductivity; the current can flow
unimpeded.
However, if high-frequency leakage currents do occur within the patient circuit, the current flowing back
and forth is generally not equal. The magnetic fields in the transformer UE1 do not cancel each other out;
Motherboard