Loud humming When I turn on the heater unit, heat is generated but the unit makes a loud humming noise. Is this possible the power supply/transformer going bad?

is it only in heat? Possibly the heater contactor but I don't believe nordyne uses a contactor. could possibly be the transformer humming? many different strange noises come from units, may want to have it serviced.

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Transformers make noise..
If transformer is buzzing, then it has probably gone bad.
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Gene

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I think you have a 110 volt machine on which you are using a step down transformer. If so it seems that the voltage from the transformer is high or the current factor requirement is also insufficient . which can produce the hum or heat. Make sure the voltage is steady or else you will need to use a stabilizer or a proper power supply that is actually catering to the requirement of the machine. You have not mentioned the power factor of the machine and i suspect that the power supply used externally is insufficient.

Disconnect the HV transformer leads from the magnetron and the capacitor. Make sure none of the wires are touching the chasis or other parts. If the loud humming sound is still present, it is the High Voltage transformer making the noise. If the noise goes away, it is the High Voltage Capacitor going bad.

*MAKE SURE TO UNPLUG UNIT BEFORE TOUCHING ANY OF THE HIGH VOLTAGE LEADS! ALSO, DISCHARGE THE CAPACITOR BY SHORTING THE TWO SIDES AGAINST EACH OTHER!

This is a LCD tv,it dosen't have a fan inside this tv.The humming sound u hearing it is comming from the tv power supply board itself.Some how those high voltage transformers,in the power supply board are having gapping voltages tranmitting,when power up those transformers are going in and out of it highvoltage coils.Tries websites like Shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.

What amplifier is this? Humming noise is normally caused by video cables in audio ports, high voltage wires too close to audio wires, or ground loops.

sounds like a crack in the magnetron
a bad transformer
or a bad rectifier
sorry i cant be more help

The "buzz" you hear is a power hum made by the power supply transformer. It's technically called "Lamination hum" caused by the revering of electrical current through the power supply transformer. In some cases the hum can vibrate the chassis causing other loose material to vibrate. If you can, go to your dealer and check to see if other units of this same type typically make a hum this loud, and if not, see if he can solve the problem for you.

Usually a humming noise is a transformer going bad.

Almost certainly, the component called the "magnetron" has died. This is the valve (tube in the US) which actually generates the microwaves. The loud humming is the transformer that supplies the magnetron being overloaded and/or the magnetron itself. If the rest of the appliance is OK and not too old, the magnetron can be replaced. If you aren't familiar with these appliances, you *must* get this done by someone who understands the dangers of messing with them - if you get it wrong, they can bite! In some countries, only qualified engineers can buy the spare parts. In the UK, the part costs around £40 - £80, depending on the model. If the appliance is more than around three years old, it may be a false economy to repair it as other parts may fail soon after the repair.