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fuse blows after running 2., 3 seconds. transformer bad?

hello, it’s GE, model number peb2060sm1ss that I am trying to fix. I pulled apart and checked all parts. all seems okay except for transformer and diode.

The oven runs without primary to the transformer. The fuse does not blow.

I disconected megatron, capacitor , diode from transformer and connected primary only. The fuse blows.

since the over runs okay without transformer connected, (only fan runs without primary), I eliminated door switches.

Since the fuse blows without connecting to megatron, capacitor, diode, I eliminated those as well. I have new diode and capacitor installed though

so I checked primary, secondary and high voltage from transformer. nothing is shorted. The only thing I noticed is resistance between high voltage and core(body) is 0.03 ohm. From what I goggled, it needs to be higher than that. 75-200ohm? I am not sure what it means.

Should I just replace the transformer?..or is there anything else i should check or am I checking wrong?

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Hi @noltian ,

Where did you read that there should be a resistance of 75-200 Ohms? Was it between the winding and the frame of the transformer as it seems a little high? But that may depend on the actual transformer I suppose

If you did measure the resistance of the secondary winding between the HT lead and the frame with the transformer isolated from the circuit and it read 0.03 Ohms then replace the high voltage transformer as it is faulty.

Update (10/19/2020)

Hi @noltian ,

Check that you have connected the diode around the correct way.

Is there a wiring diagram on the inside of the cover of the microwave?

I couldn’t find the wiring diagram for your model but here are two images showing how GE microwave ovens are wired. Essentially they are the same. Check that the wiring in your oven connects the same way from the transformer outputs to the other components.

I thought that the transformer connections were a plug in type so that they only connected the one way but maybe not.

Block Image

(click on image to enlarge for better viewing)

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@jayeff

thanks.

i watched some youtube video on how to check transformer.

I measured primary...0.01...the secondary. 0.05...check the short by connecting the wire to the body(insulated so i had to scratch abit). infinite for this.

then I measure the single wire(high voltage) to the body(scratached as well)...0.03. You tuber was saying this should be much higher than that...

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@noltian

If you're measuring 0.03 between the high voltage wire from the secondary winding and the body of the transformer then the secondary winding in the transformer is short circuit.

The transformer is faulty and needs to be replaced.

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@jayeff

hello, i found the transformer was shorted and replaced. the fuse will not blow any more. However, microwave still will not work. when it turned on, magnetron makes a click sound but it does not seem powered on. light is on and table turns. I don't hear hum sound from magnetron

any idea? is there any plus and minus from transformer?. I couldn’t remember the exact location but thought it wouldn’t matter which wire goes in to magnetron.

I replaced diode and capacitor already. Thermal switch checks out

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