I have started doing some small repairs on MSX computers and I started with cleaning keyboards on the Sanyo MSX2/MSX2+ machines. I already cleaned these from the top side (without opening the machine) but some machines would still not work correctly. So I took it to the next level and found it is actually not to difficult so I I documented the process for anyone finding himself in possession of one of these machines with keyboard issues:
1. After removing the screws from the bottom and removing the top cover the keyboard kan be easily detached from the mainboard.
2. By gently pushing against the clips (1 row at a time) the metal plate will come loose and the membrane is exposed:
3.Remove the membrane gently to expose the underside of the top cover (which is where all the dust ends up):
4. Blow away the majority of the dust and remove the rest gently by hand or with a brush:
5. There will be some dust stuck to the membrane, clean it of with a slightly damp cloth:
6. It will then look like this:
7. Replace the membrane and make sure it sits flush and all the clips go through it. Then reattach the metal back plate and gently push the plastic top plate so the clips lock in place, make sure all clips are locked (otherwise some keys won't work).
8. Turn the keyboard around and gently remove all smaller keys (the ones without a small metal stabiliser). I do this with a normal bread and butter knife which I place under one side and slightly push op (using the key next to it for leverage) and giving some counter pressure by hand (so the key won't jump away). Place the keys with their springs upside down and in the reverse order on your workspace. Then clean the baseplate with the damp cloth:
9. For each key replace the spring first, clean the key with the damp cloth on all sides and push the key down back into the base plate:
Good job!