Bosch Microwave Control Panel Not Working

[maladu]

We have a Bosch Microwave HMC80251UC/01. The control panel stopped working. We pulled it out and found a blown fuse. We replaced the fuse but after putting it back in the control panel is still not working. We have a spare control panels and tried that one as well with no luck. What else could be wrong? 

[Vance R]

22 minutes ago, maladu said:

What else could be wrong? 

There is a switch to sense if the door is closed. Most microwave won't program if it "think" the door is open. Since the fuse has blown it would be a good idea to check all the interlock swithes.

[maladu]

Would this also cause the display to stay blank, which mine does. Or if the door switches are bad is the display on but you just cannot activate the microwave?

 

[Vance R]

38 minutes ago, maladu said:

if the door switches are bad is the display on but you just cannot activate the microwave?

Typically the display will be on and the board won't accept any commands.

[maladu]

In my case the display doesn't come on. I measured the voltage going into the microwave, i.e. both phases have 120V. Both fuses worked when I put the microwave back. I heard that after the fuse it's usually the diode goes out. How do I check that the diode is ok when the diode is still soldered to the board? Also what else should I check that could cause the display to stay blank? 

[Vance R]

21 minutes ago, maladu said:

How do I check that the diode is ok when the diode is still soldered to the board? Also what else should I check that could cause the display to stay blank? 

The dirty way is to ohm them out while still in the board. The better way is to unsolder one end. 

 

Need to check for 120 vac at the board cn1  pins 1 to 3.  Double check L1 to L2 for 240 vac.