Enraf Nonius Radarmed 650, Service Manual

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Enraf-Nonius B.V. Radarmed 650 Service Manual 1409773
Description January 2000
2-2
The high voltage required for the magnetron is supplied by transformer TR2 (see app. B fig.
10). The H.F. power is controlled via the output power control resistor R1, resistors R2 and
R3 series circuit which are switched as a voltage divider.
When the output power control resistor is turned in clockwise direction the resistance is
decreasing and the output voltage at transformer TR2 is increasing. Capacitor C1 is charged
via the diode on the distributor PC Board during the half of the mains period corresponding to
the selected dosage (voltage).
2.1.5 Distributor module (distributor PC Board).
The function of the distributor module is to select and distribute the high voltage required for
the magnetron supplied by the high voltage transformer TR2.
Description of the distributor module:
The secondary voltage of TR2 which is supplied to the distributor module can be switched by
different combinations of connecting the wire. Connecting the wire (combinations will result
in the following voltages:
- CN3 to CN2 (1900VAC),
- CN6 (2000VAC),
- CN3 to CN11 and a connection from CN2 to CN8 (2100VAC),
- CN3 to CN11 and a connection from CN6 to CN8 (2200VAC).
These connections are used for rough setting of the maximum output power see app. B
fig. 7. For adjustment of the secondary voltage (output power adjustment) see par. 4.6.2.
2.1.6 H.F. output module (magnetron)
The function of the magnetron is to generate the H.F. output with a fixed frequency of
2450MHz (± 50 MHz). The H.F. output is depending on two parameters:
- the charge of the buffer capacitor,
- the output voltage of the high voltage transformer TR2 (for schematic diagram
see appendix B fig. 10).
Figure A. Principle drawing of the magnetron control circuit.
At the positive period of the power supply transformer TR2, capacitor C1 will be charged.
The charge (Q) of the capacitors depends on the setting of the output power control.
At the negative period the transformer supply voltage and the capacitor voltage are series