Microwave powers up but no function
Panasonic inverter nn sn966s displays 8888 and then nothing works with the keypad. What is this
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I can't find a service manual for a 996. The 8888 comes from a power on reset cycle that is driven from the main board. The kbd is input to the main board. Without a schematic, it is hard to say what on the main board is bad. If the common things, switches or HV diode were bad, you would still be able to use the kbd to set time, etc. Since nothing works, something on the main board is malfunctioning.
I would remove the main board and first do a careful visual for any overheated resistors or expanding capacitors. Then try to test first all the diodes then the transistors on the board with a DVM. I say "try" because sometimes it is not possible to test them in circuit. If you find a questionable one you can remove it and retest it. However, if they are SMD parts, it will be difficult to remove/replace.
Otherwise, it is something else on the main board and you need to replace the board. I have a 997 schematic and there are a couple of PCBs. One has a power supply. If yours has more than one, do the above on it also.
PLEASE BE AWARE, THAT YOU MUST INSURE THE HV CAPACITOR IS COMPLETELY DISCHARGED AFTER OPENING IT UP.
Otherwise, you may become the problem. Refer to vidios on Youtube, if you don't know how to do that.
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by iRobot
@ryanljohnso6423 this particular Panasonic model has issues with bad Keypads. Try this first. Unplug the unit for about 10 minutes. Then consider that the 88:88 is what shows when you need to set the time. See if you can do that. Also try this:Hit the start button three and see if you get a Key icon on the display. That is the Child lock which locks the keypad. To turn it off hit Stop/Reset three times. See if that frees up the keypad. If that does not work, I'd suggest to replace the keypad and re-evaluate.
by oldturkey03