Microwaves
Microwaves are generated by two magnetron the special position of the magnetrons let achieve an optimal distribution of microwaves without any need of additional antenna or moving parts.
The reflection effect that make possible microwaves reach back the magnetrons is strongly reduced but it’s relevant, to avoid damages, avoid using 100% of power especially with small loads.
Warning: microwaves system is protected by a carter to highlight the danger of the HV on this area. Never operate the unit in microwaves without the carter
MICROWAVES MONITOR
To grant a safe activity is mandatory to avoid any microwaves leakage, this meams that door must be closed to activate the magnetron.
Contacts B1 and B2/BM must be adjusted to grant that opening the door will stops the microwaves also in case of failure/unproper adjusting/modifications.
Warning: a bad adjustment can cause a short with consequent burning of EML - EMN
The operation of the microwave system is controlled and is based on the status of:
Inputs I47-I48 (B3 contact)
I4 input (I/O board)
FM Input (M Expansion)
Warning: Error messages are displayed if the fault persists for at least 10 seconds
HV Transformer
Frequency related
HV transformer 50Hz LA19200820
HV transformer 60Hz LA75187320
There are 2 HV transformers one per each magnetron
The high voltage transformer, powered by the Power board, transform the standard power voltage up to 2000Vac.
Warning: dangerous voltages on the unit only expert technicians can operate.
Warning: on the HV protection box are marked the colours for the HV transformer cables which are reversed to let them work in opposite phase
Warning: transformer is connected to the capacitor and to the magnetron with HV cables; in case of damages only replace HV cables do not try to rebuild lost connections.
HV Capacitor
Frequency related
HV Capacitor 50Hz LA19200530
HV Capacitor 60Hz LA19200660
The High Voltage capacitor is supplied together with his discharging diode and resistors
The LC circuit to activate the magnetron need a Capacitor.
Warning: Before to act on the HV area disconnect the unit from the power and discharge the HV Capacitors
Warning: Keep separated the electrical connections between the circuit of the 2 magnetrons
Warning: To check the capacitors you must disconnect them and test with appropriate multimeter.
Magnetron
As just described the magnetrons are electronic resonance cavities and generate a characteristic frequency, 2,450GHz, they are connected to the cavity by a wave guide with drive the microwaves on the cooking chamber
Magnetron is a microwaves generator and operate as a thermionic valve; means there an activation time of about 10 seconds.
The magnetron need a proper air-cooling flow
WAVEGUIDES SHIELDS
Microwaves are injected in the cabinet trough a window on the side of the cabinet, one per side. The window is covered by a microwaves transparent material which must seal the cabinet avoiding grease and dirty reach the waveguide and magnetron
In according to the prescribed maintenance or in case of damages due to unexpected replace the window shield.
Warning: apply only the same shield type as per original version
Left interlock B2 + BM
adjustment
A) Open the door and closing back search for the click of the microswitch; if click come just before complete closing or doesn’t come after closing proceed with adjustment
B) Loose lightly the screws 1
C) With door closed search for the click screwing/unscrewing the bolt 2
D) Fix the screws 1
E) Check again the adjustment after heating the cabinet at high temperature
F) Verify microwaves leakages (less than 5mW/cm2)
Left safety microswitch grant that when the door is properly closed the circuit to power the magnetrons is closed
It’s activated by the left door hinge when the door is closed. One of the micro is the power switch the second one is the monitor that will cause a short on the power line if first one fault.
Warning: The interlock must be adjusted in case of door/hinge replacement.
Right interlock B1
adjustment
A) Open the door and closing back search for the click of the microswitch; if come just before complete closing or doesn’t come after closing
B) Loose lightly the screws 1
C) With door closed search for the click screwing/unscrewing the bolt 2
D) Fix the screws 1
E) Check again the adjustment after heating the cabinet at high temperature
F) Verify microwaves leakages (less than 5mW/cm2)
Right safety microswitch grant that when the door is properly closed the circuit to power the magnetrons is closed.
It’s activated by the right door hinge when the door is closed.
Warning: The interlock must be adjusted in case of door/hinge replacement.
Interlock system
Microwaves system is managed by the MB, B1 and B2 microswitches which work together with the door micro B3 and operate by powering the power board and the base board.
The control of the micro acts according to the status of
- B3 port contact and the power supply that to give full consent by feeding with
- I4 of I/O board must have 230V to activate microwaves
- Inlet F – M of the power board.
To generate an alarm message is needed that the anomalous condition stays for at least 10 seconds.