How to reblace Rubber contact 12 not strip yamaha 2100?

It is usually caused by poor contacts between the keypad and the conductive rubber strip under the keys.
The rubber strip comes as a complete part.

Aquire the service manual and record the part number.
Speak to Yamaha or one of their agents to obtain a spare part.

Yamaha's have little rubber "contact strips" that run under the keys. These strips have little rubber buttons on them, exactly like your tv remote. When you push the key down, it pushed the rubber button down and make an electrical contact. These buttons eventually fail and separate where the bottom of the button meets the strip. You have to replace the strip (different sizes, depending on where on the keyboard it is) but they aren't cheap. You can find them here http://syntaur.com/yamaha_psr.html but sometimes you can find someone selling them on ebay cheaper. If you only need a single strip, or maybe two, it's probabaly worth it. More strips than that and you may find it cheaper to buy someone's broken keyboard on ebay and take the strips out, especially if it's broken for a different reason, like won't power up.

HI this is probably cause by the rubber contact failing.
Under each key is a rubber strip which acts as a switch against a PCB when the key is pressed.

Clean or Replace the strip and all should hopefully work again.

Part is either WF212202 or WF212402 depending on the location of the faulty note.

https://www.beckettsmusic.co.uk/shop/scripts/prodView.asp?idproduct=18846

https://www.beckettsmusic.co.uk/shop/scripts/prodView.asp?idproduct=23443

Hi this is probably cause by the rubber contact failing.
Under each key is a rubber strip which acts as a switch against a PCB when the key is pressed.

Clean or Replace the strip and all should hopefully work again.

Part is either WF212202 or WF212402 depending on the location of the faulty note.

https://www.beckettsmusic.co.uk/shop/scripts/prodView.asp?idproduct=18846

https://www.beckettsmusic.co.uk/shop/scripts/prodView.asp?idproduct=23443

Clean or replace the rubber contact pads.

If these are semi weighted keys here is a cut and paste from a manual:
19. Disassembling the Keyboard Assembly
* After inserting a round stick (Rod: TX000670)
between the frame and the keys, remove the
circuit boards. (Fig. 23)
19-1 GHD EBUS L, MK SUB Circuit Board
(Time required: about 12 minutes)
Remove the seven (7) screws marked [260A]. The
GHD EBUS L and MK SUB circuit boards can then
be removed. (Fig. 24, Photo 5)
19-2 GHD M Circuit Board
(Time required: about 12 minutes)
Remove the five (5) screws marked [260B] and the
screw marked [262]. The GHD M circuit board can
then be removed. (Fig. 24)
19-3 GHD H Circuit Board
(Time required: about 12 minutes)
Remove the four (4) screws marked [260C] and the
screw marked [262]. The GHD H circuit board can
then be removed. (Fig. 24)
* Keys can be removed without removing the
circuit boards.
* After removing the GHD EBUS L, GHD M and
GHD H circuit boards, and the rubber contacts
can then be removed.
19-4 Rubber contact
Remove the GHD circuit board for the involved key.
The rubber contacts can then be removed.

The rod is inserted above the weighted hammer and the bottom of the keys from one end. It appears to be about 1/4 inch diameter dowel and will run the full length of the keyboard. You might use 3 foot ones from each end.

Screws are removed and the boards removed without taking the individual keys out.

My keyboard yamaha psr2000,so I want parts silicone rubber keypad 61 and including electronic board,thank you.

rubber contact strip requires replacement

This is a common problem with Yamaha keyboards. The problem is caused by worn-out rubber contacts in the keyboard assembly. In my old Clavinova CLP-500, there was one long rubber contact strip under the keys with two parallel strips of semiconductor material. The Clavinova circuitry determines key velocity by measuring the timing between when the key hits the first and second strips of semiconductor material. The harder you play a key, the less time it takes the key to hit the second semiconductor strip after hitting the first.
After years of playing the keyboard, the keys eventually cause tears in the semiconductor material and this messes up the timing measurement for key velocity. The only solution is to take the keyboard apart and replace the rubber contact strip with a new one.
I got rid of my CLP-500 four or five years ago and got a new CLP-170. The CLP-170 is now having exactly the same problem that the CLP-500 had. Yamaha has re-designed the rubber contacts in the CLP-170 so that there are now eight individual contact strips instead of one long one. The problem is essentially the same, though. You have to take the keyboard apart and replace the worn out rubber contacts.
Here are the part numbers for the rubber contacts that need to be replaced in the CLP-170: V8286600 Rubber Contact, 12 keys, D-C#   Qty. 6 V8286800 Rubber Contact, 11 keys, A-C#   Qty. 1 V8286700 Rubber Contact, 5 keys, D-C   Qty. 1
I suggest you also get a copy of the CLP-170 service manual, part number 001677. It has descriptions of all the steps necessary to take the thing apart and put it back together again. You'll also need a "rod" (which is just a long dowel), part number TX000670. Before you take the circuit boards off the keyboard assembly, you have to insert the dowel between the keys and the frame to keep the keys from falling back and getting in your way. A 5-foot long 1/4-inch dowel will probably work. (I haven't yet taken apart my CLP-170, and I don't have Yamaha's "rod," so I'm not sure if 1/4 inch is the right size or not. I'll report back here if it's not.)
Good luck, Howard