Goes off, cannot use full range of volume control, now two are not working, intermittent

Anything I tell you is going to be a guess, since there has been no testing done, and we don't have the model number of the specific radio involved. However...
For a 20 year old radio, the volume and balance is almost certainly controlled by a potentiometer that has input into one leg of the fixed resistance, and the other leg (of the fixed resistance) is grounded. The movable center tap is the output to the amplifier - and its position controls the volume to that channel. If the ground leg becomes disconnected (broken wire, or a cold solder joint, or even a break in the resistor within the body of the potentiometer) then instead of "dividing" the volume, it simply provides a slight resistance inline - short answer: It goes full volume.
You can try running the control full range back and forth, and even just the old time "slap it" approach, to see if you get any static or change. If you do, that pretty well confirms the diagnosis. [If not, it just means the break is not close to touching - still almost certainly the right answer though.]
Only fix is going to be disassembly. You then may be able to find the break (and resolder it), and/or replace the volume potentiometer. Note that if you have remote volume/balance control (controls on the steering wheel), then there is some extra wiring that can likewise be involved. jk

If this is intermittent if could be bad connections on the control board. After shutting off the power try removing the connectors one at a time from the control board and reattaching them. This will usually fix any bad connections on the board. If it continues the control board may need replacing

There is a wiper on the back of the volume control that varies the resistance through the switch to control the volume. When you move it back and forth you are scraping the oxides off the switch and making it work again. I suggest you either get some contact cleaner and spray the control from inside (where the wiper is) or just change out the switch.

Volume control on the audio amplifier may have contact resistance problem some where. Look for solder problem or replace the volume control?

This is due to the signal reception. Some channels are broad casted with strong signal strength. Therefor you will find the audio is louder than other channels. Also, if there is voltage fluctuation/surges/spikes that is also responsible for suddenly increasing the volume. Best is to put a voltage stablizer

Make sure you connected your record player in the right inputs. Better try it to a line level auxilliary input that is sure to pass the volume control. hope this helps..

Since the problem appears only after the unit has been run for a while, I'd be looking for any part close to a heat source. The odd behavior suggests that there is noise on the data lines for the volume control chip and the digital processing areas. Look for a bad 5V regulator +/or bad caps on the 5V line. Also check for poor solder connections in the power supply and final output stages.
Keep us posted.
Dan

While the set is playing tap or slap the side of the cabinet, to see if the picture flickers or goes off. (This is a deep dark secret technique of expert technicians :) )
If it does then you have an intermittent connection in the electronics, which will have to be repaired at a service shop.

i fixed by unplugging the microwave with the door open. I plugged it back in and the F6 was gone. I was then able to set the clock and turn the light on/off . When I closed the microwave door, the F6 came back on and the microwave was making a humming noise. I slapped the side of the microwave near the keypad, and the F6 cleared from the readout and the humming stopped. The microwave is working fine now. Don't know why, except maybe slap on the side reset a relay or something. Anyway, I will never by a Sears Kenmore appliance for the rest of my life. The door rattles when you open a close it (like a part inside the door is broken) and this is the second time a fault code has appeared during use. I had GE Profile appliances at my last house, which are more $$ initial cost, but who wants to screw around buying a new microwave every four or five years. I'll happily spend a couple hundred more for the peace of mind and knowing that it will work during Thanksgiving dinner with the family over.

You have either a bad burner or a bad control for same, or bad connections.

With power removed use a pair of pliers to crimp the connections (after cleaning the ones on burner) going to the burner.