I have a 2004 Sharp R-1214 1100 Watt Microwave and the card like removable 3 x 4 inch plate broke (almost like cardboard) and it covered the vented opening. I don't have a users manual so I don't know the part description or number. Are they replaceable?

The cooktop light bulb(s) is(are) located on the underside of the microwave oven, and is(are) replaceable. Remove bulb cover screw, and open the bulb cover. Replace bulb, close bulb cover, and secure with screw. Cavity light: The cavity light bulb is located behind the vent grille at the top front of the microwave oven, under the bulb cover, and is replaceable. Remove 2 screws on the vent grille, tilt the grille forward, and lift it out. Open bulb cover and replace bulb. Close bulb cover, replace vent grille, and secure with screws.
For more information, your owners manual can be viewed here (scroll to the bottom of page 4):
Maytag MMV1164WB Owners Manual Page 4

Good Afternoon Friend,

I understand that you want to know how to remove the cover on your Frigidaire microwave, model# FGMV205K. There are two different covers that you are able to remove for access to two different light bulbs.

If you are trying to change the Microwave Oven Light for inside your microwave:

1)To replace light bulb, first disconnect power to your microwave oven at the circuit breaker panel or by unplugging it.

2)Remove the louver by removing the three Hood Louver Screws.

3)Push in the upper tabs and pull the louver away from your appliance.

4)Remove the light bulb and replace with a new 20 watt light bulb. DO NOT USE BULB LARGER THAN 20 WATTS.

5)Close the Oven Light Cover by carefully pushing into place. Push the louver back into place (engaging both the bottom and top tabs) and change to hood Louver Screws.


If you are trying to change the light bulbs underneath your Microwave:


1)To replace light bulbs, first disconnect power to your microwave oven at the circuit breaker panel or by unplugging it.

2)To open Light Cover, remove the screw on the light cover.

3)Replace the light bulbs with new 20 watt light bulbs. DO NOT USE BULBS LARGER THAN 20 WATTS.

4)Close the Light Cover and secure with screw removed at step 2.

If further troubleshooting is needed, I ask that you please let me know the error codes displayed on your appliance. Hope this is helpful.

-Best Regards-
WP

This sounds like carbon build up reacting to RF energy. You need to find where the burn spot is and correct it. It's probably behind or on the waveguide cover usually on the right side of the oven cavity. It looks like a brownish-tan plate about 2-3 inches by 4-5 inches. It's actually made out of mica or plastic. If you can't find the source of this problem, it may be inside the waveguide in which case the unit is not really repairable.

is a wave cover,can be replace

It is indeed straightforward but it requires removing the 4 phillips head screws that hold the trim kit on. Then you need to remove it from the cabinet (along with unplugging the cord.) Once that is done you will need to remove the 4 black phillips head screws along the bottom part of each side, 2 phillips from the left rear and 2 security T20 screws from the right side. I found that removing the 2 screws holding the bracket on the capacitor and the front allowed me to move the light housing enough to get to the bulb. In my case the bulb had unscrewed itself. I am not a big fan of the engineering associated with this model or the labor that assembled it.

http://www.repairclinic.com/PartDetail/Waveguide-Cover/1085082 it called a wave guide

From what I could find, it should be 10 1/2 inches in overall diameter.
meowpfttpftt

It may not be cardboard - it may be a material called mica which is located over where the magnetron is located in the unit. This is a protective cover and if it is what I think it is, do not remove under any circumstances, otherwise you may render the microwave unsafe to use.

It's a little more complicated than Leo2 suggested but the general concept is correct. *NOTE: Turn off power to the microwave first before servicing it!
At the top of the microwave there are three screws.
Remove the three screws and slowly pull down from the top to get the plastic airvent out of your way.
You will notice a plastic vent with two screws. Remove the forward screw and then pull from the top of the vent to access the rear screw. Now you have access to a metal plate above the fan assembly. Remove the screws at the leading edge to lift up the plate. You don't need to remove it, just lift it up!
Now you have access to the metal box over the lightbulb. Squeeze the box and the box with the light bulb inside come out as one unit. You'll know you have the correct bulb as it is attached to two white wires. Remove the bulb. Should be a halogen 120-130 volt with 35 watt brightness. Remember, halogen bulbs should never be handled with your bare hands. The grease from your fingertips heats up and the bulb burns out prematurely. Always handle these bulbs with rubber or cloth gloves. They are expensive little sucks ($7.79 at Home Depot) so handle them with care!
Good Luck ...

Unplug micro wave.
3 screws to remove top vent.
1-screw to remove touch panel from chassis.
tilts foward disconnect wires from board . I labeled for
reassembly .
1-screw holds the touch panel electrics to face plate.
There are 4-6 snap in plastic tabs holding it in place.
you have full access to the cheap plastic hinged buttons.
I hot glued mine once but they broke after 6 months.
I found this site:http://207.234.249.73/mwd/#brands
Good pics and you can see the buttons.
They sell a replacement button for $15 . There is also a
complete service manual for the Sharp 1505 for free download.
Did I mention to unplug the microwave before starting...

Rob H