Enraf Nonius Radarmed 650, Service Manual

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Enraf-Nonius B.V. Radarmed 650 Service Manual 1409773
Description January 2000
2-1
2 DESCRIPTION
Because of the modular construction of the Radarmed 650 the description is on block
diagram level.
2.1 BLOCK DIAGRAM (see appendix B fig. 1)
The electronic circuit of the Radarmed 650 is located on 5 modules:
- Display module (also referred to as display PC Board).
- Display interface module (also referred to as display interface PC Board).
- Application module (also referred to as output stage PC Board).
- Distributor module (also referred to as distributor PC Board).
- H.F. output module (also referred to as magnetron).
2.1.1 Display module (display PC Board)
The display module displays the H.F. output of the Radarmed 650 unit. The signal used for
measuring the H.F. output is fed into the display PC Board via the display interface PC
Board. The display PC Board is a three digit LED DC Voltmeter with an maximum resolution
of 1mV.
2.1.2 Display interface module (display interface PC Board)
The display module adapts the anode voltage measured at resistors R125 / R126 on the
main PC Board. Both resistors are parallel mounted in the anode circuit of the magnetron.
The measured voltage is related to the current which flows through the magnetron and
therefore also related to the output power.
2.1.3 Application module (main PC Board)
The function of the application module is to generate the output power to drive the
magnetron.
The application module comprises the following circuits:
- Power supply circuits.
- Fuses.
- Output stages
Description of the application module:
The mains power is fed into the Radarmed 650 via a mains entrance. Inside the mains
entrance two mains fuses are found. The mains power runs via a mains filter and a mains
switch to the power supply PC Board. As soon as the equipment is switched on the fan
starts to run and the magnetron is heated. The mains supply is fed via the mains
configuration strip CNA (used for setting the magnetron heater voltage to 3.4V, see par.
4.6.1) into the primary side of the mains transformer TR1. The mains power is transformed
into 3.4V (magnetron heater), 8.8V, +/- 9.7V and fed into the power supply section of the
main PC Board.
For details and measuring points see appendix B figures 10, 11 and 12.