R-28STM - Sharp Home Appliance Service Manual (repair manual). Page 17

 

 

COMMON BREAKDOWN AND MEANS OF REPAIRING 

 
 
 
1.When starting the 
oven, the lamp is not on, 
the turntable tray can’t 
rotate and the food can’t 
be heated 

1. fuse 

broken 

2.  The primary and secondary winding of the 

transformer are short-circuited. 

3.  The earthing or the polarity of the capacitor is 

punctured. 

4.  The pilot switch can’t cut off. 
5.  The interlock switch hasn’t closed. 
6.  The power plug and the socket are not in good 

connection. 

7.  The door hook broken. 

1.  Change a new fuse. 
2. 

Change a new 
transformer. 

3.  Change a new capacitor.
4. Change a new pilot 

switch. 

5.  Change a new interlock 

switch. 

6.  Adjust the connection or 

replace it by a new one. 

7.  Change a new book. 

2.When starting the 
oven, the lamp is on, the 
turntable rotating, the fan 
cycling but the food can’t 
be heated. 

1. The primary and secondary winding, the 

filament of the transformer are open-circuited. 

2.  The magnetron filament is open-circuited, the 

magnetic steel of the magnetron broken or the 
magnetron is air leaking. 

3.  Time and power distributor broken.. 
4.  The plugs of the magnetron of the capacitor 

loosed. 

1. 

Change a new 
transformer. 

2.  Change the magnetron. 
3.  Change the time power 

distributor or the micro-
switch. 

4. Fix 

them. 

3.The food can be 
heated, but the lamp is 
not on. 

1.  The lamp broken. 
2.  The plug fall off. 

1.  Change a new lamp 
2.  Insert the plug again 

4.The food can be 
heated but the turntable 
tray is not rotating. 

1.  The turntable motor broken 
2.  The plug fall off 
3.  Connecting shaft weave broken 

1. Change the turntable 

motor 

2.  Insert the plug securely 
3.  Change the weave 

5.The oven can heat 
within 2-3 minutes, but 
can not heat from the 
fourth minutes. 

1.  The winding of the fan motor in open-circuited.
2.  The fan falls off 
3.  The plug of the fan motor falls off 
4.  The turntable shaft is griped with the motor 

bearing. 

5.  The cooling vent blocked 

1.  Change the fan motor 
2.  Change the fan 
3.  Insert the plug 
4. Overhauling 

them 

5. Repairing 

it 

6.When starting the 
oven, it can’t heat, and 
with “wenwen” noise 

The high voltage diode was punctured 

Change a new diode 

7.The oven can heat,but 
with sound “shishi” noise 

The iron core of the transformer loosed 

Change a new transformer 

8.Large amount of 
microwave leakage 

1.  The door deformed 
2.  The door metal net cracked 
3.  The gap of the door crack is too large 
4.  The welding point of the oven fall off 
5.  The screws which fix the magnetron loosed 
6.  The wave guide connection oxidized 
7.  The magnetron copper filament washer is too 

thin cause the wave guide opening not in good 
earth. 

1.  Mend the door 
2.  Change the door 
3.  Adjust the gap 
4.  Change the oven 
5.  Tighten the screws 
6.  Scrape the oxidized and 

tighten the screws 

7.  Thick the copper filament 

washer 

9.The door can’t open 

1.  After  long  time using, the wear and the rust-

eaten enlarged the gap of the door shaft and 
the shaft hole, thus cause the door crooked. 

2.  The door hook broken 

1.  Adjust the hinge to rectify 

the position of the door. 

2.  Change the hook 
 

10.The door release 
button fall off 

Wore aged after long time operating 

Overhaul it or renew it 

11.Electricity leaking 

The  earthing  insulation resistances of all the 
motors or the transformer are less than 2 mega 
ohm. 

Test where is the leaking 
place, then repair it or 
change those damaged 
components.