Question about Sharp Microwave Ovens

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Turntable operation microwave was inoperative due to power surge, i replaced the fuse link on the main power board, operation was returned but when the door is opened the turntable turns and when the door is shut the turntable stops. is this a problem or is this normal operation. do not have the owners manual or service manual. thankyou,

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  • dbolick Sep 07, 2008

    sharp mod. r-7a82; origional problem was caused by a power surge which opened the fuse link on the main power board. i connected the second fuse link on the main board and operation returned but now the turntable runs when the door is opened and stops when the door is shut. thanks for your help.

  • William Miller
    William Miller May 11, 2010

    Please reply back with your model number so we can help you.

    It sounds like either a shorted relay or relay-driving component on the circuit board, or a problem with a door switch or door switch mount/



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I would suggest that you check the door switches and mounts. Here is a file to help:

If those check out, I would suspect a shorted relay or shorted relay-driving transistor.

You may be able to find a schematic of the control unit at the Sears parts site. (They are closed during overnight hours CST)

The best place to order Sharp parts is Tritronics.

Feel free to contact me directly for more information & help.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

William E. Miller

Posted on Sep 07, 2008


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LG ldg3016st has no power on main control panel

Did you have any power surges in the house? Any thunder storms?? even if you are not using a microwave, but it is plugged in , you see the clock?? That means it is getting power and running the clock so while you may not be cooking in it, it is actually using power to run the clock functions. So, if there was a power surge, it damages a part on the main board called the Low voltage transformer. It takes the 120 volts from the wall and drops it down to the voltages the board needs to operate, sometimes 5,12 24 or maybe 30 volts. If the primnary winding gets damaged from a surge of some sort. it will no longer light up if that small transformer was damaged. That can happen without even blowing the fuse as the small wires in the transformer were never meant to carry the 15 or 20 amps the fuse is rated at. So the transformer goes bad and the unit is dead but no blown fuse. Have to check the primary winding of the low volt transformer to see if it has continuity. If not, will need new main circuit board. Sorry But $$$$$

Sep 16, 2017 | LG Microwave Ovens

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Microwave portion malfunction


Did you mean that the microwave oven won't turn on at all?Did you try replacing the fuse?

May 24, 2008 | GE Advantium SCA1001SS Convection /...


Troubleshooting Guide

  • Problem: Totally dead oven.
    Possible causes:
    1. No power to outlet (blown fuse or tripped breaker or GFCI).
    2. Blown main fuse - likely due to other problems.
    3. Open thermal protector or thermal fuse.
    4. Defective controller or its power supply.
    5. Clock needs to be set before other functions will operate (some models).

  • Problem: Totally dead oven after repair.
    Possible causes:
    1. Cabinet screws replaced in incorrect location (safety interlock not engaged).
    2. Any number of screwups. :)

  • Problem: No response to any buttons on touchpad.
    Possible causes:
    1. Door is not closed (some models).
    2. You waited to long (open and close door to wake it up).
    3. Controller is confused (pull plug for a minute or two to reset).
    4. Defective interlock switches.
    5. Faulty controller or its power supply.
    6. Touchpad or controller board contaminated by overenthusiastic cleaning.
    7. Defective/damaged touchpad.

  • Problem: Oven runs when door is still open.
    Possible causes:
    1. Damaged interlock assembly.
    2. Cooling fans (only) running due to bad sensor or still warm.

  • Problem: Oven starts on its own as soon as door is closed.
    Possible causes:
    1. Defective triac or relay.
    2. Controller is confused (pull plug for a minute or two to reset).
    3. Defective controller or its power supply.
    4. Touchpad or controller board contaminated by overenthusiastic cleaning.
    5. Defective/damaged touchpad.

  • Problem: Oven works but display is blank.
    Possible causes:
    1. Defective controller or its power supply.
    2. Broken display panel.
    3. Oven needs to be reset (pull plug for a minute or two to reset).

  • Problem: Whacked out controller or incorrect operation.
    Possible causes:
    1. Previous or multipart cook cycle not complete.
    2. Controller is confused (pull plug for a minute or two to reset).
    3. Defective controller or its power supply.
    4. Touchpad or controller board contaminated by overenthusiastic cleaning.
    5. Defective/damaged touchpad.
    6. Defective sensor (particulalry covection/mirowave combos).

  • Problem: Erratic behavior.
    Possible causes:
    1. Previous or multipart cook cycle not complete.
    2. Bad connections in controller or microwave generator.
    3. Faulty relay - primary (or HV side, much less commonly used).
    4. Defective controller or its power supply.
    5. Bad contacts/connections on mechanical timers. Intermittent fuse.
    6. Power surge at start of cook cycle confusing controller.
    7. Microwave (RF) leakage into electronics bay.

  • Problem: Some keys on the touchpad do not function or perform the wrong action.
    Possible causes:
    1. Touchpad or controller board contaminated by overenthusiastic cleaning.
    2. Defective/damaged touchpad.
    3. Controller is confused (pull plug for a minute or two to reset).
    4. Faulty controller.

  • Problem: Microwave oven does not respond to START button.
    Possible causes:
    1. Defective START button.
    2. Faulty interlock switches.
    3. Door is not securely closed.
    4. Faulty controller.
    5. You waited too long - open and close door to wake it up!

  • Problem: No heat but otherwise normal operation.
    Possible causes:
    1. Blown fuse in HV transformer primary circuit or HV fuse (if used).
    2. Bad connections (particularly to magnetron filament).
    3. Open thermal protector or thermal fuse.
    4. Open HV capacitor, HV diode, HV transformer, or magnetron filament.
    5. Shorted HV diode, HV capacitor (will blow a fuse), or magnetron.
    6. Defective HV relay (not commonly used).

  • Problem: Timer and light work but no heat, cooling fan, or turntable rotation.
    Possible causes:
    1. Defective (lower) door interlock switch or door not closing fully.
    2. Faulty relay or triac.

  • Problem: Fuse blows when closing or opening door:
    Possible causes:
    1. Defective door interlock switch(s).
    2. Interlock switch knocked out of position.
    3. Misaligned door.

  • Problem: Loud hum and/or burning smell when attempting to cook.
    Possible causes:
    1. Shorted HV diode, magnetron.
    2. Burnt carbonized food in or above oven chamber.
    3. Shorted winding in HV transformer.
    4. Frayed insulation on HV wiring.

  • Problem: Arcing in or above oven chamber.
    Possible causes:
    1. Burnt carbonized food deposits.
    2. Exposed sharp metal edges.

  • Problem: Fuse blows when initiating cook cycle.
    Possible causes:
    1. Defective interlock switches or misaligned door.
    2. Shorted HV capacitor.
    3. Shorted HV diode.
    4. Shorted magnetron (probably won't blow main fuse but HV fuse if used).
    5. Defective triac.
    6. Old age or power surges.
    7. Defective HV transformer.
    8. Short in wiring due to vibration or poor manufacturing.

  • Problem: Fuse blows when microwave shuts off (during or at end of cook cycle).
    Possible causes:
    1. Defective triac (doesn't turn off properly).
    2. Defective relay.
    3. Shorting wires.

  • Problem: Oven heats on high setting regardless of power setting.
    Possible causes:
    1. Faulty primary relay or triac or HV relay (not commonly used).
    2. Faulty controller.

  • Problem: Oven immediately starts to cook when door is closed.
    Possible causes:
    1. Shorted relay or triac.
    2. Faulty controller.

  • Problem: Oven heats but power seems low or erratic.
    Possible causes:
    1. Low line voltage.
    2. Magnetron with low emission.
    3. Faulty controller or set for wrong mode.
    4. Stirrer (or turntable) not working.
    5. Intermittent connections to magnetron filament or elsewhere.
    6. Faulty primary relay or triac or HV relay (not commonly used).

  • Problem: Oven heats but shuts off randomly.
    Possible causes:
    1. Overheating due to blocked air vents or inoperative cooling fan.
    2. Overheating due to bad magnetron.
    3. Bad connections in controller or microwave generator.
    4. Faulty interlock switch or marginal door alignment.
    5. Faulty controller.
    6. Overheating due to extremely high line voltage.
    7. Stuck stirrer fan resulting hot spots detected by sensors.

  • Problem: Oven makes (possibly erratic) buzzing noise when heating.
    Possible causes:
    1. Fan blades hitting support or shroud.
    2. Vibrating sheet metal.
    3. Vibrating transformer laminations.
    4. Turntable or stirrer hitting some debris.

  • Problem: Oven light does not work.
    Possible causes:
    1. Burnt out bulb :-).
    2. Bad connections.

  • Problem: Fans or turntables that do not work.
    Possible causes:
    1. Gummed up lubrication or bad motor bearing(s).
    2. Loose or broken belt.
    3. Bad motor.
    4. Bad thermostat.
    5. Bad connections.

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2 Answers

Ge md# 3670

if you are familiar with Micro oven servicing follow these steps

.Repairing a microwave oven is a dangerous task. The high-voltage potential combined with the high-current capability of an operating microwave oven pose a deadly threat to a careless worker
1.Shorted Magnetron tube.
2.Replace Magnetron tube
3.Check Built-in surge protection on printed circuit board has opened. This circuit consists of a fine foil pattern (or filter coil - depending on the model) that acts to fuse the primary side of the low-voltage transformer.
4. Rebuild the surge protection circuit. Replace the varistor
5. Magnetron filament connectors have loosened and, due to resistive heat, the terminal connections have deteriorated and burned off.
6. Repair defective terminals as follows:Either (1) Cut away burned wire, clean the magnetron terminals, and replace the slip-on connectors, or (2) Cut away burned wire and connector(s). Clean terminals to prepare for soldering. Solder filament leads directly to magnetron terminals. Be careful not to apply soldering heat any longer than necessary
7. Check for Weakened fuse clips in the fuse receptacle causing fuse to melt due to resistive heat. Usually indicated by a bead of solder leaching out from either endcap and/or evidence of overheating (or burned spot) at the endcap, fuse clip, or terminal connection

8. Replace amp fuse and receptacle. Generic fuses and fuse holders are available at appliance and electronic part suppliers.
9. Contact service center .. all the best ..thank you

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1 Answer

LIGHT, turntable, and fan don't come on

follow this test and fix it. God bless you
  1. Exhaust fan motor If your exhaust fan motor is not running, there are a couple of things that you can check involving the motor to locate the problem. After removing the fan motor, you can manually attempt to turn the fan blades with your hand. If the fan motor is working properly, the blades should spin effortlessly. If this does not occur and the blades are taught, the motor will need to be replaced. Secondly, the fan motor itself can burn out due to time and usage. Using an ohm meter, the exhaust fan motor should read open for continuity. If it does not, then the fan motor has expired and will need to be replaced.
  2. Thermostat Another part that could cause the microwave exhaust fan to not work is a faulty thermostat. A thermostat gauges the air temperature, which activates the exhaust fan when required. If this part becomes flawed, the exhaust fan will not energize and the thermostat will need to be replaced.
  3. Main control board If your exhaust fan is still not working and the microwave fan motor, wiring, and thermostat are operating accurately, the root cause could be with the main control board. Replace the main control board.

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1 Answer

Change Motor but turn table does not turning?

test the following steps and fix it. God bless you

Turntable Motor

If the microwave turntable doesn't turn the turntable motor might be worn out. This is a common problem and relatively easy to replace.


Touchpad and Control Panel

If the microwave turntable doesn't turn the touchpad and control panel might be defective. This is not common. Test the turntable motor first.


If the microwave turntable doesn't turn and the touchpad has a button to turn the turntable on and off the touchpad might be defective. Check the turntable motor first, that is more likely.

User Control and Display Board

If the microwave turntable doesn't turn the turntable motor might be worn out. This is a common problem and relatively easy to replace. If the motor is good, the user control and display board may be defective.

Main Control Board

If the microwave turntable doesn't turn the turntable motor is usually the problem. If the motor is good the main control board might be defective

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1 Answer

Nn-t664sf no power

Check the power plug and also the mains supply to the main board. Please disconnect the power to check the continuity. Check the main fuse and if blown the main capacitor and surge capacitor.

Make sure that the program controller is working if not check power - step down supply, the pads are responding- if not faulty pads- or the door switches, if the switch contact are not good then it will not trigger the processor to switch on the waveguides. If the lights or fan work without any display or action of program being triggered to start then it can be a possible fault on the main board or the processor. Sometimes insect secretion can short the board and display panel and so the processor can work in such an erratic manner. If so clean, solder and reset the board. Now identify the parts by clicking this link:

If there is no heating please do not switch on unless you have confirmed the fault. It is possible that the Magnetron is faulty, the temperature cut off is faulty or the main capacitor is short. It is also quite possible that insect can get into the oven and create soft spots. When you switch on these will create a short and make the voltage jump and in the long run damage the magnetron. Check this link to know how a microwave works:

So Remove cover after disconnecting , check for dirt/moisture in the cabin, if so wipe clean and dry, check the magnetron and area clean and use an jet air to clean off. Check the wave guide covers, if food had deposited
then it must be checked or replaced. See link:

Jan 30, 2013 | Panasonic Microwave Ovens

1 Answer

We have a Hotpoint RVM1435WJ01 above the range microwave. We lost our electricity one day due to an outside electric wire splitting - when the electric company fixed the wire, the power came back to...

A mains surge may have taken out the fuse. To find the fuse, remove it from the mains, remove the outer cover and follow where the power cable enters the case. There will be a PCBoard with a fuse on it.
Always replace the fuse with one of exactly the same type and value!

Mar 21, 2011 | Hotpoint RVM1435 Microwave Oven

1 Answer

My maytag microwave lost power

There is always a fuse inside a microwave.Sometime this has only blown due to a surge,and upon replacing, the microwave will continue working.If it is something worse the fuse will continue to blow.In this case it could very well be the transformer,but there are other possible causes as well.(for example the control board or a short.)

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Turntable, lights and fan inop

I'm guessing that nothing is that right? If so, first guess is the breaker or an internal fuse. Nearly all units have them. You don't say what fuse you checked. Unplug the unit, remove the bulb and see what is in the socket. Next, open the breaker and then turn it back on. This will reset it. Something caused this.

Dec 19, 2007 | Magic Chef CMV1000B Microwave Oven

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