Hi,

Can you give me some idea how much it might
cost to replace a magnetron?

Too much if we buy it from Panasonic

NN-S760WA 1300watt

These units are not 1200-1300 watts...they have this high output for
the first 30 seconds or so and then they cut back to approx 1000 watts
for the rest of the cooking time.

Your model should have ( wouldn't come up online, might be too new ) an
inverter in it = no capacitor like older models. The inverter makes the
power for the magnetron and the inverters have given us much troubles.
The mag should have a 5 year warranty and the rest of the unit was 2
years. Don't check for any fuses as the fuse will shut down the entire
unit and not just one part of it. Don't mess too much with the inverter
style microwave, take it in and have it checked if you truely want to
see if it is worth repairing or not.

JMO!

jeff.
Appliance Repair Aid
http://www.applianceaid.com/