ULTRATHERM 908i
14
gbo Medizintechnik AG 2004
Version 1.2
output power. Via the resistor network R465/R466 this arrives at pin P0.2 of the processor. R465
is provided for tuning the output power of the unit.
This circuit realizes two additional monitoring functions. A thermistor (R003) is provided at the
heat sink of subassembly A200 for checking the temperature of this subassembly. It is connected
to X401.4. R439 is a component of a voltage divider whose output value is measured at pin P0.3.
The voltage across the power stage of subassembly A200 is monitored through the voltage divider
R440/R441 whose feeding point is connected to X401.8.
The diodes V401 to V405 and capacitors C407 to C425 meet protective and RF interference
protection functions.
3.2. Description of the Overall Wiring Diagram
The power supply of the
ULTRATHERM 908i
is realized by the mains transformer T001 and the
A100 subassembly that is connected with the 115 V or 230 V, 50 Hz/60 Hz, mains via mains input
A001, RF interference protection filter A002 and mains switch S001. The unit is adjusted to the
corresponding mains voltage by the manufacturer. The 45 V output voltage of T001 is required for
generating the supply voltage of the power stage of subassembly A200. The voltage is rectified by
bridge G001 the positive pole of which is connected to X205. In the other DC path there is
arranged thyristor V001 which is triggered by the operating voltage control circuit of subassembly
A200 and charges capacitor C001 in dependence on the generator output power. This is
synchronuously performed to the mains frequency, where the 26 V voltage of T001 between X205
and X203 is used. The regulated DC voltage between X205 and X201 is superimposed by a
serrated AC voltage of different amplitude and frequency.
C001 is discharged via the R002 resistor. The supply voltage of the control circuit applies between
X204 and X205.
The two DC voltages of +15 V (X206) and -15 V (X209), with their reference point X210, are
required for the analogous circuits of subassembly A200 and preamplifier. They are prepared in
the power supply module A100 (SK6.3 and SK6.4). The relay contact K001.1 which interrupts the
supply of the preamplifier under emergency-off condition is connected in series with the positive
signal path. The DC fan motor M001 is supplied with the negative voltage after a voltage
reduction by diode V002. Capacitors and Filters C002 to C019 are applied for certain measures of
the RF interference suppression.
A400 is fed via plug connector SK5 of subassembly A100. At SK4.1 the emergency-off switch is
connected to +5 V and the power relay K001 to -15 V (SK4.4). When the -15 V circuit is
interrupted, the contact opens and switches off the power of generator A200. The plug connectors
SK4 to SK6 are connected electrically in parallel and their common reference point „COM“ lies
on the casing potential.
The remaining part of the circuit was already described in the above description of the sub-
assembly. Finally, it is to be mentioned, that with any service work particularly care is to be taken
to the earthing connections given in the wiring diagram because they are decisive for maintaining
the low RF interference suppression level.
