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Voltage dips, power cuts and the microwave fuse in Nellore

Why a microwave heats slowly on Nellore evenings, why it dies after a power cut, what the internal fuse does, and whether a stabiliser or surge protector helps.

4 min read · Updated 19 August 2026

Two microwave complaints in Nellore are really electricity complaints. The first is an oven that heats slowly in the evening and fine in the morning: that is voltage. The second is an oven that is completely dead the morning after a power cut: that is the surge on restoration blowing the internal fuse. Neither means the oven is bad. Here is what is going on and what is worth doing about it.

Why low voltage means weak heating

A microwave's transformer, capacitor and diode take mains voltage and step it up to a few thousand volts for the magnetron. The output of that chain tracks the input. When the mains sags on a summer evening, the magnetron gets less, produces less, and your cup of water takes longer to get hot. The oven draws nearly full current the whole time, so you also pay more for the same job.

How to tell voltage from a failing magnetron:

  • Slow only in the evenings, fine by day: voltage.
  • Slow at all hours and getting slower over months: magnetron.
  • Slow and a new harsh hum: magnetron.

If it is the oven, the Not Heating diagnosis on our rate card is ₹399 and tests the magnetron, capacitor and diode. If it is voltage, no part will fix it.

What the fuse does, and why it blows

Inside the outer cover, near where the cord comes in, is a ceramic fuse. It protects the oven from two things: a surge on the supply, and a fault inside — especially a door interlock switch that has failed. The interlock circuit is designed so that if one switch fails, another shorts the supply and blows the fuse on purpose rather than let the oven run with the door open.

That design is why replacing the fuse is not a five-minute job. A fuse that blew on a power-cut surge will be fine once replaced. A fuse that blew because a switch failed will blow again immediately. The technician checks the switches and board first, and then fits the fuse. A Not Starting visit is ₹350 and covers exactly that.

The fuse is behind the cover, next to the high-voltage capacitor, which can hold a dangerous charge long after unplugging. This is not a home job.

Power cuts: what actually hurts

The cut itself does nothing to a microwave. The restoration is the risk: a brief surge, or supply that flickers on and off a few times before it holds. That is when fuses go and, occasionally, control boards. Two habits cover most of it:

  1. Unplug or switch off at the socket during a cut, especially in monsoon storms. Plug back in a minute or two after supply has settled.
  2. Do not leave it mid-cycle. If power drops while it is running, switch it off at the socket before power returns, then restart.

A surge-protector socket between the wall and the plug is a low-cost extra layer and is worth having during the October–December lightning season.

Stabiliser, surge protector or inverter?

Surge protector. Worth it. Cheap, passive, catches the restoration spike.

Stabiliser. Only if your supply is routinely low — not just occasional dips — and only one rated well above the oven's load. A microwave draws 1,200 to 1,500 watts heating and more for convection; an undersized stabiliser is worse than none. Many homes do not need one for the microwave at all.

Inverter or UPS. No. A normal home inverter cannot carry a microwave's load, and trying it trips the inverter or runs the oven on poor supply. Reheat later or use the stove.

The socket and wiring

A lot of "voltage" problems start at the wall. A thin extension cord, a loose socket, a multi-plug shared with the kettle and mixer — each drops voltage under load and heats up doing it. Use a 16 A earthed socket on its own, plug in directly, and replace a plug or socket that is warm or discoloured. A warm plug is an electrician visit, not a microwave one.

Earthing matters for a microwave more than for most appliances: a metal cavity, a high-voltage circuit and a damp kitchen. If the case gives a tingle, stop using it and have the earthing checked.

When to call

  • Dead after a cut with a live socket: Not Starting, ₹350.
  • Heats slowly at all hours or the hum has changed: Not Heating, ₹399.
  • Fuse has blown more than once: there is a fault behind it; say so when booking.
  • Stops and restarts by itself in the afternoon heat: check placement and vents first; if those are right, book Noisy Operation or Not Heating and mention the pattern.

Parts are at MRP and shown before fitting. And the one rule stands: switch off at the socket, unplug, and do not open the cover.

Questions people ask

Why does my microwave take longer to heat food in the evening?
Evening voltage dips. The high-voltage side of the oven steps mains voltage up for the magnetron; when the mains drops, so does the output, and heating slows. It is not a fault in the oven. If it is slow at all hours, or much slower than last year, that is a tired magnetron instead.
The microwave died the moment power came back after a cut. What happened?
Most likely the internal fuse blew on the surge when supply was restored — the same surge that sometimes takes TVs and chargers. The fuse is behind the outer cover and is a technician job. It should be replaced only after checking the door switches and board, because a fuse also blows when a switch has failed.
Should I buy a stabiliser for the microwave?
Usually not as a first step. A plain surge protector socket and a dedicated 16 A point are the useful protections. A stabiliser helps only if your supply is routinely low and it is rated well above the oven's load. Ask the technician about your specific supply rather than buying one on reflex.

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