Microwave settings switch off after 22 secs/30 secs

put a cup of water in the cavity and set for 1 minute, after which time you can feel the temperature. Switch to the other power setting and repeat with a fresh cup of water. This will either be hotter than the first or much cooler. Most microwaves use 100% power for full and 30% power for defrost, with 50% usually being lower or medium power. Straight-forward physics. The more power the hotter the water becomes. Hope that helps.

Replace the door interlockswitches - or try re-positioning the existing set. They wear after time

1 Use the number buttons to set a cooking
time. You can set a time from one second to
99 minutes, 99 seconds. To set a time over
one minute, enter the seconds too. For
example, to set 20 minutes, enter 2, 0, 0, 0 .
2 If you want to set the power level to
something other than High, press the Power
Level button, then use the number buttons
to enter a power level.
Power Levels:
Level Cooking PL
1Warm10
2Low20
3 Defrost 30
4Medium Low40
5Medium50
6 Simmer 60
7 Medium High 70
8 Reheat 80
9 Saute 90
10 High Hi

Hope that helps.

There is a main switch on the lower left side, as well as a standby switch on the front. Make sure the main switch is on, and the press the power button on the front. It will warm up & be ready to make a cup of coffee (about 30 sec.) when you select one of the coffee (cup) buttons.

sounds as either inverter or magnetron is faulty difficult to diagnose although when mag fault usually runs for about 22 secs inverter fails sooner around 5 secs.

magnetron will need replacing poss

Assuming yours is a model KHMS2050SSS0, here is what the technical sheet says about the F7 error code:

1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Unplug microwave oven or disconnect power.
4. Check cooling fan operation
5. Check the magnetron.
6. Check P65 connection on the relay control board.
7. Check the P56/P66 connection between relay board and relay control board.
8. Check wiring to the 1200W inverter and control system. See “Checking Inverters.”
9. Check operation of all interlock switches.
10. Replace all parts and panels before operating.
11. Plug in microwave oven or reconnect power.
12. Check voltage at 4903-1 on relay board. If it is 120, unplug microwave oven or disconnect power.
13. Replace inverter.
14. Replace all parts and panels before operating.
15. Plug in microwave oven or reconnect power.
16. If problem persists, unplug microwave oven or disconnect power.
17. Replace relay control board.
18. Replace all parts and panels before operating.
19. Plug in microwave oven or reconnect power.
20. If problem persists, unplug microwave oven or disconnect power.
21. Check for reversed plug connection on controls or loose wiring.
22. Replace all parts and panels before operating.
23. Plug in microwave oven or reconnect power.

(This troubleshooting guide presumes one does not know how to test electronic components. That's why they say to replace and part and check it again.)

You can find helpful exploded view diagrams and order parts by entering your full model number from the tag on the oven here.

If yours is a different model number, please reply back.

If it stops after 22 seconds, that means the controller has detected a problem, usually a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced in inverters, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here.

In Canada, you can find an authorized Panasonic servicer here.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

The 22 seconds is the giveaway.

In most cases, this is a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

I would recommend that you contact your nearest Panasonic-authorized servicer. You can find one here.

We're happy to help and we appreciate your thoughtful rating of our answer.

possibly a self-diagnostic service that detects a non-functioning magnetron