Microwave LG LMV1630 st is totally dead after power outage

check the fuse first
How to Fix Microwave Oven Simple Fuse Replacement

Dead appliance, power on wall outlet.

YOUR SAFETY IS PARAMOUNT!

Attempt this only if you are competent.

If your appliance has absolutely no functions at all, remove it from the mains supply, remove the case and see where the mains lead goes in to the appliance and follow the cable until you find the main fuse.
ONLY USE THE SAME TYPE AND RATING OF FUSE TO REPLACE IT.
The usual cause of this fuse failure is the door switches are contaminated or sticking. Check the door switches before putting power back on to the appliance.
Hope this helps.

Dead appliance, power on wall outlet.

YOUR SAFETY IS PARAMOUNT!

Attempt this only if you are competent.

If your appliance has absolutely no functions at all, remove it from the mains supply, remove the case and see where the mains lead goes in to the appliance and follow the cable until you find the main fuse.
ONLY USE THE SAME TYPE AND RATING OF FUSE TO REPLACE IT.
The usual cause of this fuse failure is the door switches are contaminated or sticking. Check the door switches before putting power back on to the appliance.
Hope this helps.

from online Microwave Repair Manual: Totally dead oven (no lights, no clock, no display, no fan, no heat...)First, check power to the outlet using a lamp or radio you know works. The fuse or circuit breaker at your service panel may have blown/tripped due to an overload or fault in the microwave oven or some other appliance. You may just have too many appliances plugged into this circuit - microwave ovens are high current appliances and should be on a dedicated circuit if possible. If you attempt to run a heating appliance like a toaster or fryer at the same time, you *will* blow the fuse or trip the circuit breaker. A refrigerator should never be plugged into the same circuit for this reason as well - you really don't want it to be without power because of your popcorn!

If you find the fuse blown or circuit breaker tripped, unplug everything from the circuit to which the microwave is connected (keep in mind that other outlets may be fed from the same circuit). Replace the fuse or reset the circuit breaker. If the same thing happens again, you have a problem with the outlet or other wiring on the same branch circuit. If plugging in the microwave causes the fuse to blow or circuit breaker to trip immediately, there is a short circuit in the power cord or elsewhere.

The microwave oven may be powered from a GFCI outlet or downstream of one and the GFCI may have tripped. (Removing a broken oven lamp has been known to happen.) The GFCI outlet may not be in an obvious location but first check the countertop outlets. The tripped GFCI could be in the garage or almost anywhere else! Pushing the RESET button may be all that's needed.

Next, try to set the clock. With some ovens the screen will be totally blank following a power outage - there may be nothing wrong with it. Furthermore, some ovens will not allow you perform any cooking related actions until the clock is set to a valid time.

Assuming these are not your problems, a fuse has probably blown although a dead controller is a possibility.

While you can do some repairs on your microwave, what you don't know can kill you... even on an unplugged microwave, so make sure you understand the dangers and how to reduce them before you try anything inside a microwave. If you want to do more yourself, go to the link at the top of this post.

I assume you checked the power cord and house power circuit breaker panel... possibly tripped unrelated to your running the microwave empty.

(the following is from http://www.kellerstudio.de/repairfaq/sam/micfaq.htm#mictotdo)

The microwave oven may be powered from a GFCI outlet or downstream of one and the GFCI may have tripped. (Removing a broken oven lamp has been known to happen.) The GFCI outlet may not be in an obvious location but first check the countertop outlets. The tripped GFCI could be in the garage or almost anywhere else! Pushing the RESET button may be all that's needed.

Next, try to set the clock. With some ovens the screen will be totally blank following a power outage - there may be nothing wrong with it. Furthermore, some ovens will not allow you perform any cooking related actions until the clock is set to a valid time.

If those are not the problems, then the main fuse is the most likely suspect for a totally dead microwave.
Remember, while you can do some repairs on you microwave, what you don't know can kill you... even on an unplugged microwave, so make sure you understand the dangers and how to reduce them before you try anything inside a microwave. If you want to do more yourself, let me know and I will point you in the direction of some good resources.

check power between power cord connection and inernal fuse,start at cord connection and work way to fuse conn.eliminating possibe problem area

That was a very long duration to have set for potatoes. It would have made the magnetron burnt by exeeding the limit and findinf there was no conductive medium by moisture , it has ended up burning the magnetron.
First of all clean up the inside and clean up the point of the magnetron beam.Now confirm on the inside to be totally dry.
Disconnect power and check inside for break of fuse to the magnetron.If the microwave does not heat on testing with a cup of water , then it is possible that the magnetron is cooked.
Confirm the cost for the unit to decide on replacement.
Hope this helps.

You need to change the cavity thermostat. The unit got too hot and blew the cavity thermostat. If this is a vent-a-hood model, it will be up under the vent housing at the top (must drop microwave to change) and if built-in, it will be on the left side under the outer cover. Just remove the screws from the back and sides and right along the edge along the bottom sides. Will have 2 wires going to it from each side. Just replace thermostat and reattach molex plugs. Then retest. Should be fine after that.

Hello if you have no power at the outlet, you may have saved your microwave. If the outlet is dead go to your house electrical panel and reset the breaker or replace the fuse. if the outlet is live and the microwave still won't power on you will have to choose between repair and replacement. Definitely get an estimate before agreeing to a repair as microwaves are very inexpensive today compared to even a couple of years ago.

CHECK THE FUSE ON CONTROLL BOARD, CHECK THE CONTINUITY OF THE LOW VOLTAGE TRANSFORMER.