Question about Sharp R-1850A Convection/Microwave Oven

1 Answer

Replaced capacitor but now light won't come on

After replacing the capacitor and the fuze, the microwave now works, but the light won't come on, even with a new light bulb. Tested the bulb and it works okay in another microwave. Do you think that there may be some other problem before we put this R1850 Sharp Microwave back over the stove?

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  • Sharp Master
  • 8,820 Answers

Do you get anything on the display when you plug it in? If not, then the magnetron temperature fuse may be blown, too.

Did you get all the connectors plugged back into the circuit board if any were removed?

There may be a relay problem on the board. The following service manuals on our site may help you:

http://www.microwavedisplay.com/r1850_sm.pdf
http://www.microwavedisplay.com/r1870_r1871_sm.pdf
http://www.microwavedisplay.com/R1874_sm.pdf

I also do board repairs. Please feel free to contact me directly if you need more help.

We're happy to help and we appreciate your thoughtful rating of our answer.

William E. Miller, AS-EET
prototech@usa.net
http://www.microwavedisplay.com

Posted on Jun 23, 2008

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2 Answers

Why do Magnetrons fail? I ask this question as my microwave (2 year old integrated microwave) had a Magnetron failure. Was cheaper to replace it. Got a new integrated one (different brand) and a week into...


I have checked the Magnetron, it had a zero ohm reading, changed the fuze again, powered the unit which is a Sharp carousel convection microwave oven model R-9Z00, all lights came on tried the oven on cake setting the heater came on to warm the oven, but as soon as the the magnetron switched on, Boof the fuze blew again.
Yeas I agree I will buy a new Microwave

Nov 01, 2012 | Sanyo Microwave Ovens

1 Answer

Prestige gs25 microwave won't heat


no the problem is more than your fuze! Micro waves have a high voltage output transformer inside that goes bad. You can fix it yourself but if your not good with electronics I would have someone else do the job!

Feb 07, 2012 | Microwave Ovens

1 Answer

Fan won't run and microwave won't heat


Hello,

Investigate these three areas if your microwave won't heat

Power Diode

A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

Testing a diode

NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor.

Whether it is shorted or open, a defective diode will most likely show some sign of defect. Defective diodes will usually emit an electrical burning smell, signifying its defectiveness. Also, it may have split in two, or it may exhibit a burned crack, or possibly even a blistered spot.

A shorted diode is indicated by a loud humming noise from the high voltage transformer, and no heat produced when a cook cycle is initiated. Whereas little or no heat produced in your microwave, with an absence of a humming noise is indicative of an open diode. In either case, the diode has to be replaced.

With your microwave unplugged, and your capacitor discharged, use extreme caution to remove the lead that leads to the capacitor. You can leave the ground connection attached. The side of the diode that goes to the ground is usually marked with a dot, stripe, or arrow. Set your ohmmeter to R x 10,000 or higher. Touch the positive meter probe to the anode and the negative meter probe to the cathode to measure the resistance across the diode terminals. Remember that the cathode is on the side that goes to the ground, which is often marked by a dot, stripe, or an arrow.

A normal diode, that is a non-defective diode, will read anywhere from 50,000 to 200,000 ohms. Differences in microwave make and model account for this large range in resistance readings.

Reverse the meter probes and measure resistance while touching the positive probe to the cathode and the negative probe to the anode. Reversing the probes like this should result in a reading of infinity. Unless a bleeder resistor is present. The presence of a bleeder resistor would produce a reading of the value of the resistor.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.

Magnetron

A defective magnetron is the third possible cause of why your microwave is not heating. Test your microwave's magnetron. Replace it if it is defective.

Testing a magnetron

NOTE: Before you test this component, make sure your microwave is unplugged, and that you have discharged the capacitor.

There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:

TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron's terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.

TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.

Read the tips on the below links on how to replace your microwave oven's diode and how to discharge the capacitor.

http://www.fixya.com/support/r7088355-replace_microwave_ovens_diode

http://www.fixya.com/support/r7088317-discharge_microwave_ovens_capacitor

I hope the above is helpful.

Regards.

Nov 02, 2011 | Whirlpool GH5184XPQ Microwave Oven

1 Answer

Carosel won't turn and won't heat


Hello,

Investigate these three areas if your microwave won't heat

Power Diode

A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

Testing a diode

NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor.

Whether it is shorted or open, a defective diode will most likely show some sign of defect. Defective diodes will usually emit an electrical burning smell, signifying its defectiveness. Also, it may have split in two, or it may exhibit a burned crack, or possibly even a blistered spot.

A shorted diode is indicated by a loud humming noise from the high voltage transformer, and no heat produced when a cook cycle is initiated. Whereas little or no heat produced in your microwave, with an absence of a humming noise is indicative of an open diode. In either case, the diode has to be replaced.

With your microwave unplugged, and your capacitor discharged, use extreme caution to remove the lead that leads to the capacitor. You can leave the ground connection attached. The side of the diode that goes to the ground is usually marked with a dot, stripe, or arrow. Set your ohmmeter to R x 10,000 or higher. Touch the positive meter probe to the anode and the negative meter probe to the cathode to measure the resistance across the diode terminals. Remember that the cathode is on the side that goes to the ground, which is often marked by a dot, stripe, or an arrow.

A normal diode, that is a non-defective diode, will read anywhere from 50,000 to 200,000 ohms. Differences in microwave make and model account for this large range in resistance readings.

Reverse the meter probes and measure resistance while touching the positive probe to the cathode and the negative probe to the anode. Reversing the probes like this should result in a reading of infinity. Unless a bleeder resistor is present. The presence of a bleeder resistor would produce a reading of the value of the resistor.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.

Magnetron

A defective magnetron is the third possible cause of why your microwave is not heating. Test your microwave's magnetron. Replace it if it is defective.

Testing a magnetron

NOTE: Before you test this component, make sure your microwave is unplugged, and that you have discharged the capacitor.

There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:

TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron's terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.

TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.

Read the tips on the below links on how to replace your microwave oven's diode and how to discharge the capacitor.

http://www.fixya.com/support/r7088355-replace_microwave_ovens_diode

http://www.fixya.com/support/r7088317-discharge_microwave_ovens_capacitor

I hope the above is helpful.

Regards.

Oct 27, 2011 | Sharp R-930AK Convection/Microwave Oven

1 Answer

My microwave oven isn't heating my food. Everything else works, the fan, the lights and the keypad. The microwave turns and sounds like everything is working but the food won't get hot. It is only...


Hello,

Investigate these three areas if your microwave won't heat

Power Diode

A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

Testing a diode

NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor.

Whether it is shorted or open, a defective diode will most likely show some sign of defect. Defective diodes will usually emit an electrical burning smell, signifying its defectiveness. Also, it may have split in two, or it may exhibit a burned crack, or possibly even a blistered spot.

A shorted diode is indicated by a loud humming noise from the high voltage transformer, and no heat produced when a cook cycle is initiated. Whereas little or no heat produced in your microwave, with an absence of a humming noise is indicative of an open diode. In either case, the diode has to be replaced.

With your microwave unplugged, and your capacitor discharged, use extreme caution to remove the lead that leads to the capacitor. You can leave the ground connection attached. The side of the diode that goes to the ground is usually marked with a dot, stripe, or arrow. Set your ohmmeter to R x 10,000 or higher. Touch the positive meter probe to the anode and the negative meter probe to the cathode to measure the resistance across the diode terminals. Remember that the cathode is on the side that goes to the ground, which is often marked by a dot, stripe, or an arrow.

A normal diode, that is a non-defective diode, will read anywhere from 50,000 to 200,000 ohms. Differences in microwave make and model account for this large range in resistance readings.

Reverse the meter probes and measure resistance while touching the positive probe to the cathode and the negative probe to the anode. Reversing the probes like this should result in a reading of infinity. Unless a bleeder resistor is present. The presence of a bleeder resistor would produce a reading of the value of the resistor.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.

Magnetron

A defective magnetron is the third possible cause of why your microwave is not heating. Test your microwave's magnetron. Replace it if it is defective.

Testing a magnetron

NOTE: Before you test this component, make sure your microwave is unplugged, and that you have discharged the capacitor.

There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:

TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron's terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.

TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.

Read the tips on the below links on how to replace your microwave oven's diode and how to discharge the capacitor.

http://www.fixya.com/support/r7088355-replace_microwave_ovens_diode

http://www.fixya.com/support/r7088317-discharge_microwave_ovens_capacitor

I hope the above is helpful.

Regards.

Oct 23, 2011 | GE Spacemaker JVM1540 Microwave Oven

1 Answer

Microwave won't heat, EVERY thing else works


Hello,

Investigate these three areas if your microwave won't heat

Power Diode

A diode is an electronic component that readily passes current in one direction only and blocks the flow of current in the opposing direction. If your microwave's diode has become defective, your microwave will not heat. Test the diode to determine if this is the cause of your problem. Replace it if it is defective.

Testing a diode

NOTE: Before you test your diode, make sure your microwave is unplugged, and that you discharge the microwave's capacitor.

Whether it is shorted or open, a defective diode will most likely show some sign of defect. Defective diodes will usually emit an electrical burning smell, signifying its defectiveness. Also, it may have split in two, or it may exhibit a burned crack, or possibly even a blistered spot.

A shorted diode is indicated by a loud humming noise from the high voltage transformer, and no heat produced when a cook cycle is initiated. Whereas little or no heat produced in your microwave, with an absence of a humming noise is indicative of an open diode. In either case, the diode has to be replaced.

With your microwave unplugged, and your capacitor discharged, use extreme caution to remove the lead that leads to the capacitor. You can leave the ground connection attached. The side of the diode that goes to the ground is usually marked with a dot, stripe, or arrow. Set your ohmmeter to R x 10,000 or higher. Touch the positive meter probe to the anode and the negative meter probe to the cathode to measure the resistance across the diode terminals. Remember that the cathode is on the side that goes to the ground, which is often marked by a dot, stripe, or an arrow.

A normal diode, that is a non-defective diode, will read anywhere from 50,000 to 200,000 ohms. Differences in microwave make and model account for this large range in resistance readings.

Reverse the meter probes and measure resistance while touching the positive probe to the cathode and the negative probe to the anode. Reversing the probes like this should result in a reading of infinity. Unless a bleeder resistor is present. The presence of a bleeder resistor would produce a reading of the value of the resistor.

High Voltage Capacitor

A capacitor is an electrical device which stores electricity. A defective capacitor may be why your microwave is not heating. The capacitor will have to be tested to determine if this is the cause of your problem. A defective capacitor will have to be replaced before your microwave will work again. Make sure you discharge the capacitor before you test it, though.

Magnetron

A defective magnetron is the third possible cause of why your microwave is not heating. Test your microwave's magnetron. Replace it if it is defective.

Testing a magnetron

NOTE: Before you test this component, make sure your microwave is unplugged, and that you have discharged the capacitor.

There are two tests to conduct in order to determine whether or not a magnetron has become defective. If you receive results other than what are detailed below, you will have to replace your microwave's magnetron. Each test is described for you here:

TEST 1: Locate your magnetron and label each of the wires attached to it so that you know which wires are to be replaced where. Set your ohmmeter to the lowest resistance scale. Take a resistance measurement between each of the magnetron's terminals by touching each probe to one terminal each. Reverse the probes and take a second resistance measurement. Each measurement should read less than one ohm.

TEST 2: Set your ohmmeter to its highest resistance scale. Touch one of the meter's probes to a magnetron terminal. Touch the other probe to the metal magnetron housing. Take special caution to not touch the two probes together. This could result in an inaccurate reading. This test should produce a reading of infinity - indicating an open circuit.

Read the tips on the below links on how to replace your microwave oven's diode and how to discharge the capacitor.

http://www.fixya.com/support/r7088355-replace_microwave_ovens_diode

http://www.fixya.com/support/r7088317-discharge_microwave_ovens_capacitor

I hope the above is helpful.

Regards.

Oct 14, 2011 | Whirlpool MH7140XF Microwave Oven

1 Answer

Microwave won't heat, timer goes off after 1 minute or so


Microwaves are a quick, convenient solution to the hassle of preparing and cooking hot dinners. They are popular appliances with students and large families where food often needs to be prepared fast. Microwaves use radio wave technology harnessed through an antenna, known as a "magnetron," to create friction between food or liquid molecules, causing them to heat up. Some microwaves can cease to function properly, resulting in the appliance running but failing to produce any heat.

  1. Magnetron
    • Magnetron tubes are often the source of heating problems in microwaves. Before having any repair work done, check the warranty on your microwave. Many companies offer 10-year warranties on magnetron tubes so you may be able to get it repaired professionally for free. Otherwise, unplug the microwave then remove the rear casing with a screwdriver. Locate the tube inside the microwave and check it for burn marks. A burnt tube cannot usually be repaired and will require replacement. A tube that doesn't appear burnt should be tested by a qualified technician to see if it can be repaired.
    High Voltage Capacitor
    • A microwave capacitor holds electricity as the appliance is running. A malfunctioning capacitor can lead to the microwave not heating, along with an irritating buzzing sound. Test the capacitor by first disconnecting the power then removing the wires attached to the capacitor. A capacitor with burn marks is usually damaged beyond repair and will require replacement. A capacitor can be tested by connecting each of the probes of an ohmmeter to the capacitor terminal. Each probe should provide a reading of infinity if the capacitor is working properly.
    Power Diode
    • The diode in a microwave oven is a one-way pathway that channels electricity from the capacitor. A malfunctioning diode can sometimes be the cause of a microwave that won't heat. The heating problem is often accompanied by a loud buzzing noise. You can test the diode by first unplugging the microwave oven, disconnecting the diode from the capacitor then measuring the level of electricity inside the diode with an ohmmeter. The ohmmeter can determine whether the electricity in the diode is flowing in one direction as it should. In most cases, the magnetron tube will have to replaced as well if the diode is damaged.
    Safety
    • Disconnecting the plug from your microwave to carry out an inspection does not guarantee safety. Even an unplugged microwave still has electricity running through its components, which can lead to severe electric shocks. Unless you have previous experience in dealing with electrical appliances, it is advisable to hire a technician to test component parts rather than undertake the job yourself. Anyone without a basic knowledge of electrical currents and safety should avoid testing components altogether.

Oct 03, 2011 | Microwave Ovens

1 Answer

We had a lighting storm a few days ago and now my Amana radarange will not do anything, can this be as simple as a fuze? and if so can that be replaced without removing from the wall? thanks, Dean


Hello there and thank you for choosing fixya
Yes it could certainly be the fuse and that is where i would first check and if it checks out good than you may have a fried controle board or even fried wires inside the microwave
You may even have a bad power inverter also ok
Sometimes the boards can be more expensive than the unit costs you originally so be wise to this ok
keep me posted on what you have found
best regards Mike

Aug 04, 2011 | Amana Radarange Microwave Oven

1 Answer

Microwave appears to have no power. Display is blank. Checked and found internal fuze blown. Replace the fuze with 20A ceramic fuze. Display works. When try to cook something, microwave runs for about half...


You have a short somewhere. Possible causes, defective interlock switches for the door,shorted capacitor, shorted diode, defective triac. More than likely its one of these.

Oct 01, 2009 | GE Monogram ZE1660SA Microwave Oven

1 Answer

How to replace a fuze in a ge spacemaker xl microwave oven


depending the age of the unit and its usage, if not a lot its not the fuse,but I would say its more likely a H.V. Diode,H.V. Capacitor, or the magnetron tube.

Sep 20, 2009 | GE JVM1630 Microwave Oven

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