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230V 50 HZ Microwave does not heat with my 230V 60 HZ Power Line Supply Answered

My brand new European oven that I bought did not heat from day 1. The table turns and the grill works, but the microwave function does not. I know a little about the HV transformer, the capacitor and diode and magnetron. What could be the problem ? If the line frequency is the cause what can I do to convert it ? maybe change the capacitor for one of lower capacitance ?


How does the 848IX compare to the 848IXL ?

You;re definitely getting 240 V "phase" to "neutral" ?

Good morning all, we did lots of testing last night and followed current paths because there isn't any voltage going at the primary coil. The transformer never worked,the magnetron never worked. When I first plugged in the unit the electrician told me that the two male one female plug in the appliance he was unable to find a wall plug for, so the very first time I turned on the appliance it was not grounded. Well it is grounded now, For now, it seems like a relay in the PCB board is faulty, the switch that sends voltage to the primary sort of speak.

Timer runs, motors run, everything but the MW runs, and the MW is not getting power from the circuit board.

By pass the main circuit board and power the microwave directly off service power, measure the current should only be 4 to 5 amps and see if the MW works.

But going by my experience you are looking at a rebuild.

Yes it works but we cannot do this for operation without the switches. The MW works however. Somewhere along the PCB board on both ovens the relay is not activating. What to do ?

Forgot to ask or say, Did you put a glass of water in the MW and make sure the water got hot or warm?

ehehehe yes of course !!! Josehf, the relay is not sending power to the primary upon MW start. Other relays activate for the light, turntable, and fans and timer, no voltage for the primary winding in the transformer though.

Is the solenoid of the relay getting power?

If the relay's solenoid is getting power and the one side of the points of the relay is getting power the relay is bad.

If the relay's solenoid is not getting power it is in the circuit board.

One way to be sure is to supply power to the solenoid and see if it turns on the MV.

Good Now you are sure the MW works.

Dumb time to think of it, I am not that familiar with all the options of that model, does it have a meat thermometer that automatically turns off the oven when the meat is cooked?

Make sure that option is off. You would not believe how many service calls I did for an oven repair and the only thing wrong with the oven is it was turned off by the meat thermometer or the oven timer.

If every thing but the MW works when the door is closed it is not the main safety switches, it could be a minor safety switch or thermal fuse so check all the safety switches and thermal fuses.

Have you red my Instructables on Reverse Engineering?




Follow the MW power lines from the MW to the supply power, make sure nothing is damaged or burnt.

Along the way there will be some black boxes those are the power relays for the microwave. Make sure the coils in the relays get power when you turn on the microwave.

I am a little surprised it doesn't work at all. What model is it ?

A "traditional" microwave did indeed have a big transformer in it, but the modern ones do not. I do doubt though that that will make a difference - I've been happily using my 230V English stuff that we brought to the US when we emigrated.

I'm inclined to think you have another kind of problem than the voltage rating, possibly related to the way the US supplies 230V, as two 115 volt legs

not that it does not work at all. This is a Whirlpool AMW848IXL which can be used as forced air, grill, or microwave. It is the microwave function that does not heat food.

I have the service manual downloaded. There are two fuses in the thing which would be the first thing to look at.

It DOES look like a conventional microwave internally though.

There are a bunch of safety switches which might also be at fault.

Hi Steve, yes, the turntable works fine and the light comes on. No error codes on the tablet display. But the darn water in the glass does not heat one bit. I agree with the fuses that sounds good. i don´t have this manual I will open it up and see. Are these fuses before the HV transformer primary ? I will measure if I got 230V at the primary. the lines has 234 I measured. So you are saying it has the voltage doubler capacitor and diode circuit ? OK. But if the fuse blew it was brand spanking new so maybe the higher frequency is causing too much current going into the magnetron ? Where are these fuses located please ?

thanks Steve, I have that schematic, but it is for an older model the 480ix. Looks similar but are you sure ? Aware of discharging the capacitor and only measuring voltage at the primary, no further than that.

get to the transformer, the primary terminals will be obvious. Lets see what's on 'em.

Steve, I have reached the conclusion that my primary winding is not getting any voltage because of the way we wire here at +110-110 split single phase, vs 230V single phase and neutral. What can I do to feed the oven in the way it wants to ?

Its untlikely, but I dont' unfortunately have a proper schematic. The circuit I did have would certainly work on US split supplies.

You aren't in PA are you ? ;-)

The only way round it, if there is a problem with the split, would be a big and expensive transformer. We need a service diagram !


Like I said, before I go out and sped a fortune on that big and expensive transformer that has to go for 2,500 watts power (MW and Grill), I tested with an old 175 Watt transformer that we use for other things. We got our 230V single phase still at 60 Hz and powered up under no load first then at 90W power lowest MW setting and nothing, no voltage whatsoever at the primary.

OK, we have now unpacked and tried the second oven, we bought two of these. Same thing, zero volts at the primary. When we test each line to ground one line has 118V, the other zero. When the microwave function is turned on, table starts to rotate, fans come on with 237V, and zero volts at the primary.

someone from Italy told me a while back that operating these ovens at 60 hz caused the diode to burn. Maybe because the dc current going into the magnetron did 60 times per second instead of 50. So if I find this diode to be blown what can I do to convert? Go to a .80 microarad capacitor of the actual mf value ?

No, again, if anything, you are in the direction of reduced loading on things as the frequency increase, because the diode repetitive peak current is HIGHER at lower frequencies.

But if we find the primary is energised and carrying current, and the problem looks like its on the secondary, you must GROUND everything on the secondary side, to make sure the reservoir cap is completely discharged.

You should check continuity through the primary too. There is a buried thermal fuse in there.

will do this tomorrow and report back what I find, thanks so much.

WARNING HIGH VOLTAGE, this is not a toy, it can and will kill you.

Turn the microwave on.

Does the magnetron hum when you turn the microwave on and does the timer run?

If the magnetron hums and the timer runs, it is ether the magnetron or the cycles. Just because it is new doesn't mean it works.

If the magnetron doesn't hum and the timer doesn't run, it is the safety switches or the main circuit board.

If the magnetron does not hum and the timer runs, test the service voltage coming out of the main circuit board to the HV transformer and make sure there is service voltage coming out of the main circuit board.

If the magnetron does not hum and the timer runs, and there is no service voltage coming out of the main circuit board to the HV transformer it is the main circuit board.

If there is no hum, the timer runs, and there is service voltage coming out of the main circuit board, check if there is service voltage at the HV transformer.

If there is service voltage coming out of the circuit board but it is not reaching the HV transformer check the thermal fuses.

If the microwave oven didn't work from new chances are it is not the thermal fuses, but they are easy to check with a meter.

The thermal fuse is a disk with two wires connected to it, one thermal fuse should be screwed to the side of the magnetron, a second thermal fuse may be on the oven body. To check the thermal fuses you can disconnect the wires and test continuity, or you can turn the microwave on and check the voltage at the thermal fuses terminals.

If the magnetron doesn't hum, and the magnetron's HV transformer is getting power, the magnetron is toast or you are not getting power on the high voltage side.


Test the high voltage output, test the capacitor, test the diode.

If all of these are in good working order it is the magnetron.

It is not uncommon for the microwave to not work when it is off cycles.

You may need to swap out everything from the magnetron to the HV transformer if it is the cycles.

There it is guys. Very easy to get the top plate off. It has the voltage doubler circuit, with a 2300 VAC capacitor. The capacitor is 1.15mf, tested at 1.1390 mf. It is good. The magneyron tested ok as seen in the pic, very low ohm reading. No shorts within the part. The diode appears to be shot, with a zero continuity reading on both directions. The diode apparently blew when the micro was first turned on. Any suggestions ? This particular diode denomination is CL04-12RG60I. I bought a replacement diode HV05-12F05 but dobt want to try until I hear expert advice from you guys.


I posted the wrong pic of the diode check before I adjusted for the voltage draw. But anyway nothing, the new replacement shows 5.93V DC in the correct direction. Nothing on the old diode is shot.

I was about to ask if you tested the replacement diode.

Some high voltage diodes can fool you with a high voltage drop across the diode.

Yes, I tested it and showed 5.9 V DC. Actually I bought two of them and both tested pretty close. The one I took out is completely out. I found these denominations are both good for 12,000 VAC. I am still wondering why it went out on me. Being that they both have the same, I will install and run, and measure the primary. Someone here told me however, that the transformer might be converting 230 VAC into something like 2,800 VAC instead of 2,300 VAC, and the reason why the diode might have burned.

No,the output doesn't scale with frequency, only turns ratio - which is fixed. And no one designs something without a significant design margin.

As an engineer you must know change the frequency and you change the impedance of a coil. Change the impedance and you change the output.

No, this isn't a coil (inductor), its a transformer. There are parasitic elements which are inductive, leakage inductance and magnetisation inductance. The magnetics are affected slightly by frequency, but a transformer is a mutual inductor, so both sides are affected by changes in frequency, and therefore cancels out, to a first approximation.

As I said, the effects of frequency are there - and at higher frequencies, transformers can become smaller, and some losses can increase, but for a 20% change, they are largely negligible in a well designed transformer.

What!! it isn't a coil!!

Then why is it called a primary coil and a secondary coil?

You put a meter on the primary of a microwave HV transformer and nothing on the secondary you get 0.9 ohm resistance. you connect that same transformer to a 120 volt AC supply and nothing on the secondary you get 8.7 amps or an inpedance of 14 ohms. Without the inductive reactance the current would be over 120 amps.

You up the frequency by 20% you up the reactance by 20% or 2.8 ohms.

120 x 8.7 = 1044 watts

120 / 16.8 = 7 amps

120 x 7 = 840 watts

An unloaded loss of 204 watts.

Josehf, go and read up on transformer action, you are wildly wrong. Transformers do just that, they transform voltage, they transform current, and they transform the impedance too. What's the load on the secondary ? Infinite. How does that transform to the primary ? Also, nearly infinite, so it draws no extra current, it has nothing to do with the "inductance". What you are seeing are losses, which can be expressed as inductances, capacitances and resistances.

Measure the phase of the current you are measuring with respect to the primary voltage, You will see it is a significant phase shift. The inphase component is the ONLY dissipative term.

RAISING Frequency INCREASES reactive impedance, since Z =2x Pi x f x L, so increasing F by 20% INCREASES the impedance of the inductive terms.

There IS an inductance by virtue of leakage flux and a term called magnetisation inductance, and I do not deny that as the frequency increases, those terms will have a reducing effect on the terminal impedance, since as the F increases, so does the X of the transformer.

Steve it was my job.

Someone would buy a machine from Europe and I would rewire, rewind the motors, rewind the magnets, and rewind the transformers.

European service electronics to North American standard service.

Some things you can just plug in and go, others just fry the instant you plug them in, and some only work partially.

10 cycles do not sound like a lot but it will make an induction motor go from 1750 rpm to 2100 rpm by the way the 60 cycles increases the speed of the rotating magnetic fields in the stator, and when loaded most of the motors burn because of the loss of power.

With transformers and magnets they loose power just like most motors.

You are a believer in wikipedia.


Basic transformer parameters and construction

Effect of frequency

Paragraph 3

Operation of a transformer at its designed voltage but at a higher frequency than intended will lead to reduced magnetizing current. At a lower frequency, the magnetizing current will increase. Operation of a transformer at other than its design frequency may require assessment of voltages, losses, and cooling to establish if safe operation is practical. For example, transformers may need to be equipped with 'volts per hertz' over-excitation relays to protect the transformer from overvoltage at higher than rated frequency.

That exactly matches what I have already explained, there is an "magnetisation inductance", as F increases the effect of that inductance is to icrease the reactance, and reduce current.

I am an even greater believer in experimental evidence. See my demo here.

There is essentially NO change in primary current or change in output volts over 45-72 Hz.

First you and iceng said frequency doesn't effect transformers at all or not enough to matter.

I proved that wrong.

Look at iceng's own picks, the transformers are marked with their functioning cycles.

Nice video and totally off point that is a toroid not a resonant frequency transformer like the one in a microwave.

Without the datasheet on that 50 cycle transformer it is impossible to predict what it will do.

And as I said long ago it will do one of three things.

Plug and go.

Fry the second you plug it in.

Or it will work partially.

There is a weakness in Wikipedia and transformer action. Definitely not covered are resonant HV like resonant magnetic devices and there is NO attempt to use the laminations to block eddy currents because of the thorough six welding FLUX shorts.

This suggests to me the designers were not concerned about any difficulties arising from a higher frequency. Do note the air-gap flux shorts between the primary and secondary...

Also many years ago I designed a NeoNatal Life support Cassette for premature baby birth transport and it was powered from AC_line, 12/24 vdc, half hour stand alone and military 400 cycle aircraft... The Textronix breathing / vital signs instrument worked on square wave inverter, I20 vac 60 cps to 400 cps with no transformer difficulty.


Odd, that Wikipedia fact

"transformers may need to be equipped with 'volts per hertz' over-excitation relays to protect the transformer from overvoltage at higher than rated frequency."

has never crossed my knowledge base or experiences. I'm no way discounting your life experience Josehf, perhaps that 50 Hz uWave is much different then the pictures that I went to a great deal of late night difficulty photographing that uWave irregular transformer to reveal what I believe represents air-gap control of the output voltage. And a true EI core shown here.


First you and Steve said frequency doesn't effect transformers at all or not enough to matter.

I proved that wrong.

Remember your own picks, the transformers are marked with their functioning cycles.

You can show me picks of your transformer until the cows come home but, without the datasheet on that 50 cycle transformer it is impossible to predict what it will do.

And as I said long ago it will do one of three things.

Plug and go.

Fry the second you plug it in.

Or it will work partially.

I have to agree a standard transformer output voltage is only based on turns ratio.

Josehf, thank you very much for taking the time for this detailed explanation. I will make measurements with an appliance electricician, but we will not measure the output voltage out of the secondary. I don't have this oven in front of me but as I recall the magnetron does not hum. I thought it was silent but there is no difference in sound from when I first turn on the MW and it shuts off. the timer does its cycle well, the internal light comes on, and a fan keeps going after the cycle is finished and air blows underneath until I open and shut the oven door. I will come back and report later.

downunder, if that fuse is going into the secondary could it be that the HV transformer is sending more current working with 60 hz ? I am not worried about the sturdier 50 hz transformer handling the higher frequency but the current ? I can replace the fuse but what will prevent it from blowing again ?

In an ideal transformer, the operating frequency doesn't affect the transformation properties. In a non-ideal of course it does, because the magnetic materials saturate, but in general as the input frequency INCREASES, the size of the transformer can be reduced. Since you've moved in the direction of increased frequency, and then by only 20%, you should be OK.

If somethings gone, I don't think its caused by frequency.

Steve, I took out an old transformer that I had good for 175 watts max and transformed single phase 120V 60h into 237V single phase still at 60 hz. Then powered the oven with this single phase feed. I tested for voltage at the primary and nothing, even with single phase 230V.

Is it possible that this oven´s brains has a frequency detector and is not sending voltage to the primary because of the 60 Hz ?