For MINOR ISSUES:
1) Check the metal sheet inside the oven. It is usually beside the part where you can see the light during heating.
2) If the metal sheet is worn out or burnt, remove it carefully. Just make sure that the oven is not plugged in. You can easily remove it with your bare hands.
3) Visit your service center and ask for a new sheet. It costs only P300.00. Cut it according to the size of the old one.
4) Replace it back in the oven by sling them in the small holes provided at the sides. Holah! Your microwave oven is as good as new and you saved costs from bringing them at the service center.
BEWARE: Troubleshooting is not applicable to all oven problems. Cases such as failure of the oven to produce heat may be difficult to trouble shoot and may even lead to fires. For your safety, better buy a new one if that is the case 🙂