Microwave ME21F707MJT ghost touch issues - FIXED

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written by owen on 2023-Feb-26.

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It started happening about a year into the 4 years of owning the microwave.  Mostly at night you would hear the beep of a number being activated.  This would happen at nights most once or twice a week.  Over time it progressed to the 3 touches, which could usually be ignored until it started activating the LED light, then the vent fan and finally it started to start the microwave itself which was a clear sign that it could not longer be ignored.

First thing I tried was searching online which led to several dead ends.  I Went to the local shop that I bought it from and they said that 4 years is a good run for a microwave and quickly suggested I buy a new one.  I was willing to replace the door but had no luck finding them online.  Its kind of a curse or a blessing that the touch sensitive pad is in the door.

Next step is dismantling the door itself.  If I disconnected the door cable the ghost touches would stop indicating that the problem is definitely in the door.  It seems that even the motherboard itself is inside the door.  Dismantling the door is a test of patience itself - I suggest you search for a youtube video.  The first time I took the door off I removed and reconnected the ribbon cables.  Some people online say that this is a quick fix because sometimes the cables become twisted or disconnected slightly.  After that I reassembled the door and waited patiently.  After about an hour the random ghost touches returned with a vengeance.

At this point we started unplugging the microwave and plugging it in only when we needed to use it.  But this was a temporary fix as the microwave started to cancel itself while food was being heated, lol.  There is an option to turn off the beeps but that bearly when you never know when the microwave is going to activate something that makes a sound like the fan or the light.  So with all my options exhausted I had to go back into the door.

The solution that worked for me

So I waited until I had a day entirely to myself - empty house.  I took the door off the microwave, carefully rested the parts and the screws in the couch.  The pan for this trip is to clean the circuit board with a can of circuit board cleaner.  Since I did not have that particular cleaner on hand I used regular rubbing alcohol.  When you dismantle the door carefully unclip and remove the ribbon cable from the main circuit board.  I placed some alcohol in a small cup then I applied it to the circuit board with a soft makeup brush.  The main purpose of the alcohol is that it evaporates quickly and the soft brush is to gently apply the alcohol without damaging the board.  I cleaned the whole board, back and front, both ribbon cable tips and then I let everything air dry.
After it dried I brushed it with alcohol again, all the leads, circuits then let it dry again.  I clean the brush after every wipe to ensure that any residue/dust gets removed instead of slushed around.  After all that I reassembled everything and the ghost beeps stopped.  The touch pad has also become more responsive since the clean up.  No more missed touches.  So far its been 3 weeks.  Problem solved.

Additional thoughts

I think that over time dust and static might have built up on the circuit board.  These electronics must be suffering from heat death or something.  Since the fix I have been unplugging the microwave at night since there is no real reason to leave it plugged in when not in use.  There is easy access to the power plug for all the users so this is not much of an inconvenience.  I hope to eke out another 2 years out of the microwave because otherwise its a perfectly good device.
I hope this helps someone out there save some money and not contribute to the world's waste.

Update Nov2023

Roughly 8 months later the dreaded ghost beep has returned even with the routine unplugging of the microwave when not in used. I promptly removed the door again and redid the procedure. We will see how long it lasts this time. Note that the plastic grill (the first thing you unscrew) at the top of the microwave is very brittle so you want to be careful with that - mine is already broken in 2 places.

Update Jan2024

Spontaneous after a quick cleaning of the front with windex all the buttons except 2 have stopped working. I am not sure if its the windex that cause the this new issues since the entire interface is just glass but I am forced to divide into the door again because the touchpad is now entirely unusable.

Update Feb2024 1

So cleaning the motherboard with alcohol and reseating the ribbon strip works to restore the functionality but I have no clue why it happens so I unplug the microwave after every use. Might need to invest in a switch.

Update Feb2024 2

Microwave went dead again almost a week after the previous cleaning. I figure that its time to buy a new one but I was not ready to give up as yet. I figured that there is something that I am missing. So I got up early in the morning after the wife left for work and started a process of taking off the door, cleaning one part then reattaching the door in order to test what started working. I took the door off ten times. lol. Only a patient man rides a donkey. Anyway on the 5th attempt I noticed that I was losing function in some buttons and by the 9th I only had 2 buttons left. Cleaning the board the connectors and ribbon cable did nothing. Until I took a look at the ribbon cable for the 2 sides of the panel.

It appears that the ribbon cable is decaying at the contact point where it clips down onto the motherboard. If you look care fully you should see a discontinuty need the edge of the cable where the clip presses the connectors. So what did I do? I cut off 4 mm off the edge of the ribbon cable. This allowed it to sit deeper into the socket. I cut the same amount off each side because both sides of my microwave were equally dead. It would seem at cleaning with alcohol really did not do anything but really all you need to do is reposition the ribbon cable. First step reposition, then clean and in the worst case cut it VERY CAREFULLY with a sharp, small scissors. Make sure the cut is perfect straight or you will have alignment problem.

I am typing this right after doing the procedure and everything seems to be working fine again - instantly apart from 2 unimportant buttons. Will report back if it fails again but I think this will be good for another 6 years. At while point I possible have space for one more 4mm cut. Peace and love.

Side note: replacing the ribbon cable seems impossible as it goes into the door that is sealed is someway (probably glue). so do not mess up the CUT!

Update March2024

So its still going strong. I put some painter's tape over the connectors on the underside of the motherboard. I feel that moister is getting onto the exposed connectors. If you notice on the motherboard there are areas which have this protective wax over certain parts. It seems that whoever was incharge of painting this on missed some parts. I have no access to this wax thing so painter's tape is my best bet. we will see how long this lasts.

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