Bosch HMV5053U/01 burning fuses

[vs01]

Hello All,

My microwave is about a year old and have been using it for 6 months. It’s gone through several fuses already but now when I replace the fuse and run the microwave for 30s smoke starts coming off the fuse. There are scorch marks on one of the fuse clips.

I tested the door switches and they seem fine. I also tested the transformer and capacitor. The transformer primary wiring has a resistance of .8 but the tech sheet says .31 +/- 5%
Is this ok or bad?

Any guidance on how to diagnose this issue?

TIA

[Metro Appliances]

That's over +150%.

Edited June 16, 2022 by Metro Appliances

[Vance R]

Start by measuring the amp draw. Next would be to replace the fuse clips or the board with the fuse clips and the fuse.

[vs01]

I know it’s out of spec, but is that reasonable to conclude that the transformer is causing the issue due to this?

 

Just to be clear, I am talking about the fuse in the noise filter. I did replace the noise filter today. The microwave starts and the fuse is hot to the touch where is was scorching/smoking on the old one.

Where would I measure the amp draw?

[Vance R]

If you have a clamp on meter any where on the incoming line. Most microwave draw 10 to 14 amp when working correctly. Monitor the incoming voltage to make sure it is not dropping below 120 vac.