MC4111L / MAG 690
Technical Training
4.5. - Door lock
The door imperatively must be closed during the magnetron operation. It is fitted with a mechanical locking
system, which controls the switches and the electrical power supply to the appliance. The switches only
operate if the door is properly closed.
This safety device consists of switches built in the low-voltage circuit, so as to allow power supply to the
transformer (and, therefore, to the magnetron), depending on the door position. A double safety device also
exists, which consists of a switch mounted in the contrary manner. It is open when the door is closed and is
closed when the door is open. When the door is closed, the switches are closed and enable the magnetron
to start. As soon as the door is opened, they open and cut instantaneously the power supply to the
transformer, and thus the emission of waves. In the event where the first safety switch would remain
closed, the back up switch would short out the low-voltage circuit and would trigger the general fuse of the
appliance, so ensuring the user's safety.
Two door locks are built in the up rights of the oven, positioned on the right and on the left underneath the
panel.
The right-hand lock integrates the secondary microswitch
and a cam.
When the door is closed, the hook actuates the cam which,
by revolving on itself, actuates the microswitch.
The left-hand lock integrates the primary microswitch, the
control microswitch which drives a cam.
When the door is closed, the hook actuates the cam, which, by
revolving on itself, actuates both microswitches.
Checked element
Test points
Ohmic value
Opened door
Ohmic value
Closed door
Primary Switch SW1 no-com Infinite
0Ω
Control Switch com-nc
0Ω
Infinite
Control Switch com-no Infinite
0Ω
Secondary
Switch SW2
no-com Infinite 0Ω
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