The short answer
The usual answer on this unit is metal or foil in the cavity, or a burnt waveguide cover, with the oven sharing a loaded circuit next. The difference between them matters to a technician and not to you: the oven comes out of service either way. Everything an owner can safely do here is outside the cabinet: the socket, the cord and the cavity.
The symptoms, and their near misses
- Sparks or arcing inside the cavity during use — Something in the cavity is arcing, and it will burn through whatever it is arcing against.
- NEAR MISS: it runs quietly and simply does not heat — That is a heating fault and it is a different page.
Causes, most likely first on this unit
- Metal or foil in the cavity, or a burnt waveguide cover — Foil, a metal trim on a dish, or a food-soiled waveguide cover arcs and burns. The cover is the small board-like panel in the cavity wall, and once it chars it arcs every time the oven runs. First, and the whole order below follows from it: it is the only cause on this page that an owner can see, and it is the one that most often turns a clean oven into a burning one.
- The oven sharing a loaded circuit — A microwave draws heavily the moment it starts. Second on this unit, because a standard household branch circuit is fifteen or twenty amps at one hundred and twenty volts, and a microwave is a large part of that on its own.
- The high-voltage capacitor, which is why the cabinet stays shut — The capacitor holds a lethal charge after the oven is unplugged and it does not discharge on its own. Bottom of the list, deliberately: it is not a fault at all: it is the constraint that governs every other cause above it.
The order to check in
- Look at the cavity wall panel for charring or holes — A burnt cover arcs on every use and gets worse each time.
- Try the oven on a different circuit with nothing else running — Working there and tripping at home is a wiring problem, not an oven problem.
- There is no owner check inside the cabinet, at any point, for any fault on this page — That is the whole of it.
Owner-side checks, step by step
- With the oven unplugged, look for a charred or holed panel on the cavity wall, and check nothing metal is being used inside — Do not run the oven again with a charred cover.
Tools: a torchAbout 10 min
- Note what else is running on the same circuit when the breaker trips — A microwave should have a circuit it does not have to share.
About 10 min
- STOP HERE: the cabinet stays shut whatever the fault — The high-voltage capacitor holds a lethal charge after unplugging. Call a technician or replace the oven.
Safety first, and it is not boilerplate
Safety
Unplug the oven and leave it unplugged. The high-voltage capacitor inside holds a lethal charge after the power is off and it does not bleed down on its own, which is why this is the one kitchen appliance an owner never opens. Do not tape, bend or defeat a door interlock, do not run it empty, and do not use it at all with a damaged door, latch, seal or window.
The line between a fix and a service call
Call, or replace the oven, if it arcs, smells of burning electrics, trips a breaker, or buzzes far louder than it used to. Have an electrician look at a plug or socket that is discoloured or warm, because that fault is in the wiring rather than the appliance.
Related pages for this unit
Scope of this page, and where to go for more
This page covers the Walmart Hamilton Beach microwave as a class, not one family or model line. Where a family- or model-specific page exists it is linked here. Deliberately not here: component part numbers, capacitor discharge procedures, high-voltage test methods and any cabinet removal sequence, none of which belong in a home guide.
Links: - [A Walmart Hamilton Beach microwave with a door that does not sit flush](/blog/walmart-hamiulton-beach-microwave-door-seal) - [A Walmart Hamilton Beach microwave with a turntable that turns and food that stays cold](/blog/walmart-hamiulton-beach-microwave-heating-failure) - [Why a Whirlpool Corporation microwave trips a breaker or smells hot](/blog/whirlpool-corporation-microwave-electrical-safety)
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
