Hello there. Magnetrons can be expensive. You didn't list your model number, so I can't be specific, but they range from 70 to 100 bucks. There are quality replacement parts which can be much cheaper. The part numbers usually start with QBP. Sometimes, the QBP magnetrons go for as little as 35 bucks. The only way to verify this is to look up your model and see if a QBP part is available as a substitute replacement for the mag in your microwave. With the hum and no heat, it definitely sounds like a bad mag. It isn't something I recommend a DYI repairs. The unit needs pulled down and there are a lot of screws to remove. It can be done, but I generally recommend that a professional handle the installation of the part. I hope this helps. If you need more information, please reply here. I'll get back with you as soon as I have a free moment. Please be patient though, as I work full time through the day. Good luck.