Stopped working - burnt elect. smell. Shut it down at the breaker. Made a humming noise after it stopped working. Is it worth repair or just buy new?

Check internal fuse? Is the front door switch working?

You're describing a common smell that goes along with a magnetron tube that has failed. The magnetron tube makes the microwaves, and will eventually fail if you keep a microwave long enough. They can fail in a couple of different ways, and one is to short out accompanied by that burning smell. It's probably not worth trying to repair your oven because of its age. I don't believe the magnetron is available any longer. If it is, it will be costly, and replacing the tube is best left to a professional because of safety concerns. Your most economical choice would be to replace the oven.

The problem is in the magnetron it has stopped working, if you open the microwave oven door sometimes you can smell what can only be described as an ozone smell and signifies the part in question. It is best to buy new "cheaper" than have it repaired "more costly"

it may have just blown the circuit breaker

the buzz noise is generally a diode or capacitor problem, capacitors generally will buzz. Definitely worth looking at. Look for a burnt diode or a capacitor with a bulging top with the power off.
Otherwise the magnetron may have gone out and then you are just better off replacing
let me know what you find Benjamin

Well, if there is not heating the food and making a loud buzzing or humming sound when it is on, then the magnetron has failed. It typically shorts out and fails. The magnetron for this cost $140 plus the cost of the service call, you're better off buying a new oven. Hope this helps.

In all likelihood the mangnetron has failed, or perhaps even the Power Supply. or a fault that is shutting the system down for safety reasons You need to have it serviced by a reputable service centre/man. Ensure you get a firm "Quote" before proceeding, and remember these days the cost of repair can equal or exceed the price of a new one.

Well your gonna have to take it down a take apart the microwave more than likely. Probably have a shorted HV diode,magnetron, shorted winding in HV transformer.burnt or frayed HV wire insulation

Check belt on fan.

This model uses an inverter to produce high voltage instead of a convential transformer system. While an inverter (switched-mode power supply) is more efficient from a power consumption standpoint, it is more complex, thus more statistically prone to fail. These should only be examined and worked on by someone who has the necessary technical qualifications. Seriously. Often the machine-soldered connections in a microwave inverter are too weak, so they eventually fail, especially if heat is high in the area. They sometimes fail catastrophically. When not catastrophically damaged, you may hear clicking or squealing and may smell an electrical odor, which is sometimes obscured by the cooling fan. Some manufacturers do not encourage or assist technicians to repair microwave inverters. Most offer the inverter as a whole assembly. But sometimes that is actually cheaper than the time and labor required to fix the old one. If a technician is willing and able to troubleshoot and repair the inverter to component level, it will may be expensive, but may be worth it, especially if he or she will resolder and reinforce connections as needed as part of a thorough repair. That could easily make your inverter beter than a new one! You might be able to get some verbal estimates if you call Panasonic-authorized repair shops and ask then specifically about inverter repair and inverter replacement costs for your model number.