JVM1850BH06 GE Microwave not heating

[bigtexun]

Model Number

JVM1850BH06

Brand

GE

Age

6-10 years

I have a ge spacemaker 1800 that isn't heating. I'm an ee that designs computers, but I thought I could fix this easily, I knew the diode, magnetron and capacitor were common replacement parts, so I bought all three before I even took the microwave down, because my wife didn't want an eyesore in the kitchen while I waited on parts. Obviously none of the parts were bad, but I replaced them anyway. The fuses are good, and the microwave almost sounds like it is working. I say almost because when it is heating normally, there is an extra somewhat harsh hum that I can hear turn on and off when I set a low power mode. That harsh hum is missing, all I hear is the lighter hum of the fan and turntable motors running, which when combined with no heating, means it is obvious something else is wrong.

The door top switch and interlock switchs seem fine, the 4 bimetal heat sensors are all showing 0 ohms, so as far as I can tell none of the interlocks are having a problem.

Is there some other part I need to be testing? The front panel behaves normally, and I don't see anything obvious burned or damaged. Is there a relay on the control panel implicated? I hear a relay click when I plug it in, and when I close the door the fan receives power for a split second and rotates a couple of revolutions (it spins normally when I try to heat something). The interior light reacts to the door opening and closing, and the computer acts completely functional and seems normal.

This is part of a matched set of kitchen appliances, so the wife is going to want to replace them all if I can't fix part of the matching set...

Any suggestions?

 

[Dan O.]

When cooking the control board sends 120V to the primary of the HV transformer. If power IS there but it is not heating, the transformer or those parts you replaced could be responsible. If NO power is there, either the control isn't switching power to that circuit or there might be a safety in the circuit preventing it.

In the latter case someone needs to check the wiring diagram in the microwave to see what other devices are in the circuit to the HV transformer which might have failed.


Dan O.

 

[Wx4usa]

That split second click and power of the motor sounds like a switch issue. Either bad or timing sequence off by wear.

You have 3 switches two are normally open one normally closed. Normal is door open.

Test the switches top and bottom NO normally open. Middle, NC normally closed. Check for differences in feel when depressed too. You could also have a worn latch body/switch holder.

As Dan O said, you can test for 120v to the primary of the transformer, easy to do at the monitor switch. Remove the monitor switch wire connector, enter 30 seconds and test for 120v at that connector you just removed. If you get 120v the issue is in the hv section. Diode, cap, mag. And if you get fan, tt and cooking lamp your thermal fuses are likely ok.

Was there a tech sheet/schematic inside the unit?

Send the FCC ID from the model label if you can.