The short answer
Stop using the oven and unplug it first; then read the list. On this machine the most likely cause is waveguide cover burnt or carbonised.
What you observe
- Sparks or a flash inside the cavity during a cycle — Arcing.
- A scorched patch on the waveguide cover at the side wall — Carbonised food on the cover, which then arcs against itself.
- A rust spot or chipped paint inside the cavity — Bare metal in a cavity arcs, and the oven should not be run.
- NEAR MISS — it runs quietly and simply does not heat — That is a heating failure without an electrical fault, and it has its own page.
Causes, most likely first on a SKS microwave
- Waveguide cover burnt or carbonised — The arcing then burns the cover further, so it gets worse with every cycle. Ranked first on a SKS microwave: a carbonised cover arcs against itself, which is why this fault always worsens rather than settles.
- Metal, foil or a metal-trimmed dish in the cavity — Foil, a twist tie, a metal-rimmed plate or a fork will arc immediately and can burn the cavity wall.
- A rack, turntable support or trim touching the cavity wall — A metal turntable support or a trim piece that has shifted does the same thing.
- Chipped cavity paint or a rust spot — The cavity coating is what keeps the steel from arcing, and a chip or a rust bloom exposes bare metal.
Check in this order, and why
- Look at the small panel on the cavity side wall for scorching or holes — Brown scorch marks or a hole in the cover is the fault.
- Look at what was in the oven when it sparked — Check the plate as well: some decorative glazes contain metal.
- Check any rack or support is seated in its intended position — A rack resting against the wall is an arcing site.
What an owner can safely check
- Unplug the oven and inspect the waveguide cover; wipe light splatter off it gently — A cover that is scorched, holed or soft is a replacement part — never run the oven without it.
Tools: soft cloth, torchAbout 15 min
- Unplug the oven, remove everything from the cavity, and check the dish and any wrapping for metal — Foil, twist ties and metal-trimmed plates all arc. Remove them and inspect the cavity wall for burn marks.
About 10 min
- STOP HERE — the outer cabinet stays on — Everything past the cavity and the door is high-voltage work, and it is not an owner job at any point.
Before you open anything
Safety
Unplug the microwave before you touch anything beyond the cavity and the door. The outer cabinet stays on: a microwave holds a high-voltage capacitor that can retain a lethal charge long after the plug is out, and it is not an owner-serviceable machine. Never defeat, tape or bend a door interlock switch — those switches are the only thing that stops the magnetron running with the door open. Never run the oven empty, and stop using it altogether if the door will not close and latch properly.
When to call a technician
The line is the cavity: what you can see and remove is yours, and everything behind the wall is high-voltage work. A microwave that buzzes loudly, smells hot or trips a breaker stays unplugged until a technician has seen it. Door and hinge work on a panelled machine is a trained job: the panel weight is carried by the hinge springs and a mis-set hinge damages the cabinetry as well as the appliance.
Nearest pages of this class
What this page does not cover
This is the generalised SKS microwave page. A family- or model-specific page, where one exists, is linked above and is the more precise answer for your unit. Left out on purpose: part numbers, connector colours, the order panels come off in, and every torque figure — a generalised page cannot be right about any of them.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
