Microwave Ovens

This page covers domestic microwave ovens.

Summary

We do not normally recommend repairing microwave ovens on safety grounds, since internally, they use very high voltages at high power. However, there are a few simple things that can be tried.

Safety

It could be EXTREMELY DANGEROUS to operate a microwave oven with the cover off, much more dangerous even than working on raw mains electricity. Even after switching off, the capacitor may hold sufficient charge for an extended period to give you a DANGEROUS, possibly LETHAL electric shock. You should NEVER remove the main cover unless you have a complete understanding of the risks.

Never work on a microwave oven when you are alone. All other people present must be warned of the risks. At a Restart Party where there may be people coming and going, never remove the main cover unless you have an assistant responsible for managing bystanders.

Simple Faults and Repairs

Always switch off and unplug the oven before doing even the simplest investigation or repair.

If there is no sign of life at all, check the fuse in the plug. However, fuses don't normally blow for no reason, and this may indicate another more serious fault.

There are just a few simple faults that can be fixed, listed here.

Failed bulb

Look for a small cover plate on the back of the oven or a window inside secured by one or more screws and which you can remove in order to access the bulb. Replace it with one of the same type, voltage and wattage.

Sparking

If you can see sparking inside the oven, the first thing to do is clean the inside thoroughly. Remove all traces of any burnt food or burn marks from the sparking itself.

Pay particular attention to the wave guide cover where the microwaves enter the oven. In a bad case, this can get burnt through. Follow these instructions to clean or replace the wave guide cover.

Plate not turning

Assuming everything else seems to work, turn the microwave upside down (not forgetting first to remove the plate and anything else inside it). Check to see whether there is any way in in order to inspect and possibly repair or replace the turntable motor and mechanism.

Door problems

There is normally a mechanical linkage on the door latch which can cause problems. This activates a switch to switch off the power when the door is opened. Access can normally only be gained by removing the main cover, which is not advised. Read the #Safety section before doing this. A broken plastic leaver or cam might be repairable but glue on its own is unlikely to hold without some form of extra reinforcement.

Timer and Controls

As with the door mechanism, access to the timer and controls may only be possible by removing the main cover. Read the #Safety section before doing this. There is some possibility that faulty buttons or switches could be cleaned or replaced, but beyond this electronic diagnosis and repair skills will be required. A mechanical timer might be improved by cleaning but failure may simply be due to wear.

Other Components

You may find websites which describe the replacement of other components, in particular the transformer, diode, capacitor, magnetron and fan. on #Safety grounds, you are strongly advised to leave these to a professional repairer. If not mated properly with the wave guide, the magnetron may cause sparking, overheating, and interference with WiFi, Bluetooth and other wireless technologies.

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