5
4. Troubleshooting
PRECAUTION
1.
CHECK GROUNDING BEFORE CHECKING FOR TROUBLE .
.
BE CAREFUL OF THE HIGH VOLTAGE CIRCUIT .
3.
DISCHARGE THE HIGH VOLTAGE CAPACITOR .
4.
WHEN CHECKING THE CONTINUITY OF THE SWITCHES OR TRANSFORMER, DISCONNECT ONE
LEAD WIRE FROM THESE PARTS AND THEN CHECK CONTINUITY WITHOUT THE POWER SOURCE
ON . TO DO OTHERWISE MAY RESULT IN A FALSE READING OR DAMAGE TO YOUR METER .
5.
DO NOT TOUCH ANY PART OF THE CIRCUIT OR THE CONTROL CIRCUIT BOARD, SINCE STATIC
DISCHARGE MAY DAMAGE IT . ALWAYS TOUCH GROUND WHILE WORKING ON IT TO DISCHARGE
ANY STATIC CHARGE BUILT UP .
4-3 Electrical Malfunction
Oven is dead . (No display and no operation at all .)
Fuse is OK
Open or loose lead wire harness
Open thermal cutout (Magnetron)
Open low voltage transformer
Check fan motor when thermal cutout is defective.
Check Ass’y PCB when L.V.T is defective.
Check adjustment of primary, interlock monitor,
power relay, door sensing switch.
NOTE 1
: All of these switches must be replaced at the same time. (refer to adjustment instructions)
Check continuity of power relay contacts and if it has continuity, replace power relay also.
NOTE:
Large contact resistance will bring lower magnetron filament voltage and cause magnetron
to lower output and/or intermittent oscillation.
NOTE 2
: When H.V.Transformer is replaced, check diode and magnetron also.
Defective Ass’y PCB
Shorted lead wire harness
Defective primary latch switch
(NOTE 1)
Defective monitor switch
(NOTE 1)
Shorted H.V.Capacitor
Shorted H.V.Transformer
(NOTE 2)
Oven does not
accept key input
Key input is not in-Sequence
Open or loose connection of
membrane key pad to Ass’y PCB
Shorted or open membrane panel
Refer to operation procedure.
Replace PCB main.
Defective Ass’y PCB
Timer starts
countdown but
no microwave
oscillation
Off-alignment of latch switches
Open or loose connection of high
voltage circuit especially magnetron
filament circuit
(NOTE)
Defective high voltage components
H.V.Transformer H.V. Capacitor
H.V.Diode, H.V.Fuse Magnetron
Adjust door and latch switches.
Check high voltage component according to
component test procedure and replace if it is
defective.
Open or loose wiring of power relay
Replace PCB main.
Defective primary latch switch
Defective power relay or Ass’y PCB
Oven does not accept key input (Program)
Fuse is OK
Open or loose lead wire harness
Open thermal cutout (Magnetron)
Open low voltage transformer
Check fan motor when thermal cutout is defective.
Check Ass’y PCB when L.V.T is defective.
Check adjustment of primary, interlock monitor,
power relay, door sensing switch.
NOTE 1
: All of these switches must be replaced at the same time. (refer to adjustment instructions)
Check continuity of power relay contacts and if it has continuity, replace power relay also.
NOTE:
Large contact resistance will bring lower magnetron filament voltage and cause magnetron
to lower output and/or intermittent oscillation.
NOTE 2
: When H.V.Transformer is replaced, check diode and magnetron also.
Defective Ass’y PCB
Shorted lead wire harness
Defective primary latch switch
(NOTE 1)
Defective monitor switch
(NOTE 1)
Shorted H.V.Capacitor
Shorted H.V.Transformer
(NOTE 2)
Oven does not
accept key input
Key input is not in-Sequence
Open or loose connection of
membrane key pad to Ass’y PCB
Shorted or open membrane panel
Refer to operation procedure.
Replace PCB main.
Defective Ass’y PCB
Timer starts
countdown but
no microwave
oscillation
Off-alignment of latch switches
Open or loose connection of high
voltage circuit especially magnetron
filament circuit
(NOTE)
Defective high voltage components
H.V.Transformer H.V. Capacitor
H.V.Diode, H.V.Fuse Magnetron
Adjust door and latch switches.
Check high voltage component according to
component test procedure and replace if it is
defective.
Open or loose wiring of power relay
Replace PCB main.
Defective primary latch switch
Defective power relay or Ass’y PCB
Summary of Contents for SMH7185STG
Page 3: ... 1 Precaution ...
