[SidAPP]

Hello,
I'm having issues with a LG LMV2053 microwave. It seems to work correctly except there is no heat. This happened after by son left the microwave on for an hour with nothing in it thinking he set the timer. There doesn't seem to be any loud noises or buzzing but I don't hear very well. Here is what I have tried so far:

1 – Disconnected the Primary Terminals from the HV Transformer.
2 – Ran a cook cycle measuring the input voltage to HV Trans = steady 123VAC.
So LV side seems to be fine. Ran the following tests on HV comps:

Magnetron:
1 – Removed all wires to the terminals.
2 – Measured resistance (R x 1) from one term to the other = 0+ ohms.
3 – Reversed leads from above, still 0+ ohms.
4 – Measured resistance (R x 1K) from each terminal to housing = infinity.
5 – Visually inspected the unit and it looks ok. Some of the fins are discolored (brown and gold) due to heat/burning. The rest look new bright silver.
6 - Put a 10 ohm resistor on the diode cathode to ground and ran the microwave. I measured .123 VDC which I've read is very low, should be -3 to -4 VDC.

Capacitor:
1 – Measured resistance (R x 1K) between the two terminals:
Initial reading = infinity
Swapped leads = High level resistance, then faded to infinity
Swapped leads again = High level resistance, then faded to infinity
2 – Measured both leads to metal case = infinity for both.

Diode:
Removed diode from circuit and ran 123VAC through it and measured 65VAC RMS both ways. The diode appears to be working as it should.

HV Transformer:
1 – Disconnected all wires.
2 – Measured resistance (R x 1) between the three Primary Terminals = .2, 0+, .2 ohms.
3 – Measured resistance between the two orange leads (filament) = 0+ ohms.
4 – Measured resistance between each terminal and chassis = infinity.
5 – Measured resistance from yellow secondary to chassis = about 70.8 ohms.

I’m leaning toward a bad magnetron. What do you think?

I would be willing to gamble on a $50 magnetron or a $85 transformer but not both. It's not worth $135. Your thoughts or other suggestions?
Thanks again for all your help!

[Simon / APP Team]

Hi.

The filament winding should give you some resistance reading, not just continuity. Also the filament voltage is normally 3.5-3.7 VAC.
If you will get parts from APP you can return any unused ones even if they been installed.

Here are the breakdown diagrams and Replacement parts for LG LMV2053SB Microwave Oven | AppliancePartsPros.com

Thank you. Post the results.

Simon.

[SidAPP]

Hello Simon,

It was hard to tell if the filament winding had any resistance. One of my meters read 0 ohms and the other more expensive one keep switching between 0 and .1 ohms. That's why I put 0+ ohms above.

Just to make sure I'm clear what are you calling the filament voltage - voltage across the resistor I mentioned above?

I took you up on the parts and went ahead and ordered both the magnetron and transformer hoping I will only need one or the other.

Thanks for your response,
Clarence

[Simon / APP Team]

You are welcome. Post the results.

Simon.

[SidAPP]

I replaced the magnetron and the microwave has worked fine for several weeks. Now the microwave has a short buzzing or hum sometimes when it's first turned on to heat. It seems to work ok other than the noise. What do you suggest? What should I test or look for?
Thanks

[Simon / APP Team]

Hi.

Sounds like the magnetron on it's last leg again.You should replace it under the warranty.

Simon.