Merrychef conneX
®
service and repair manual
High voltage magnetron test.
Ensure the following requirements have been met before starting the test:
▪ The appliance has been disconnected from the power supply and protective measures have been taken to ensure
the power cannot be switched on again.
▪ The appliance is cool.
▪ The high voltage capacitors are discharged before commencing work.
▪ The casing of the appliance has been removed.
DANGER
High voltages and significant currents are present at the high voltage capacitor and HV Circuit.
It is very dangerous to work near this part when the oven is on.
NEVER make any electrical measurements on the high voltage circuits, including the magnetron filament, whilst the oven is
connected to the mains power supply.
1. Remove all electric connections from the magnetron.
2. Using a Digital Multi-Meter (DMM), check for continuity.
Result should be as follows:
3. Connect the DMM to both terminals of
the magnetron.
The test is passed if the DMM display
reads 1 Ω or less.
4. Using a megger/insulation tester connect to one terminal
and the metal outer case of the magnetron. The test is
passed if the megger/insulation tester display reads an
infinite resistance, "open circuit". Repeat the test for the
other filament terminal and the metal outer case.
5.8 Mains voltage components (casing removed).
Convection fan: motor.
The convection fan motor is a 3-phase AC motor having a maximum speed of approximately 5200 rpm.
The windings are thermally protected. In the event of a thermal fault, the trip inside the motor (IP) will open circuit and cause
the VFD to enter a fault mode.
Convection fan: motor speed controller.
The convection motor speed controller provides a 3-phase AC switched mode drive to the convection motor and is
controlled by a 0 to 10 Volt signal from the IO board (connection X519).
This allows the motor to be adjusted from approximately 1400 rpm to 5200 rpm in steps of 1%.
▪ Door open, Approx. 1400 rpm (10% @ 1V).
▪ Door open (cleaning cool down), >100
o
C Approx. 5800 rpm (85% @ 8.5V). >50
o
C Approx. 3500 rpm (50% @ 5V).
▪ Door closed (not cooking), Approx. 2500 rpm (30% @ 3V).
▪ Door closed (heating up), Approx. 3500 rpm (50% @ 5V).
▪ Door closed (cooking), speed as specified by program or setting up to a maximum of 5200 rpm (100% @ 10V).
Convection fan: motor speed controller LED status display.
The VFD contains a diagnostic indicator (Red LED) to display the drives operational status.
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