Loss of touch sensitivity

[jdcykca]

I've got a CDP-130.

 

While I was playing, a range of 8 keys suddenly lost touch sensitivity. After a short while the next 8 lower keys lost it as well, but regained it after some more time.

 

I've taken it apart and cleaned it - even removing each key to get at the contact sensors. The rubber contact strips are in good condition and clean.

 

I noticed each key has two contact sensors - the rubber "buttons" each have two conductive pads: one is longer than the other and would contact first. I assume that velocity sensitivity is achieved by measuring the time interval between the two contacts. I tested "normal" keys by closing only one contact at a time - no sound. Only when both contacts are closed is there sound. When I do this on the "defective" keys I get a full velocity sound just from closing either one of the contacts.

 

The circuit board the contacts are on looks pretty simple - no ICs or anything, just what appears to be a single transistor for each key. There is no visible damage and the solder joints look healthy on all the transistors. The ribbon cables look good too.

 

Any suggestions?

[Jokeyman123]

You are correct about the time intervals-and here is where the trouble can lie. Each boot-if you look very carefully-you will see is a tiny bit different-one is shorter than the other-has a shorter "throw" when pressed in-so depending upon how you hit the key-will determine the timing between each rubber bumper contacting the IC contacts below as you said. This is one of the more difficult repairs I have come across. The only solution-that I know will (mostly) work-if this is the problem-is to replace the rubber strips with new ones-and have to be an exact replacement-you can't replace these with something that appears to be the same-it probably will not be. And since this is happening on a range of keys-I would suspect the rubber strips-although there is a possibility that the connector cable from the keyboard to mainboard has slipped out-even a tiny movement form these cables can cause this same problem-unless it is hard-wired-all the Casios I have worked on have pressure-slip ribbon connectors-just have to pulled out or pushed  in, these can move over time-usually not but possible so look at that.

 

What makes this type of malfunction difficult to assess-the rubber bumpers can look perfect-i suspect that after much playing-these boots become slightly compressed-and lose their "geometry"-even the tiniest distortion in these d****ed boots will ruin dynamic response. As far as other components-i've tested 100s of the matrix diodes in many boards-almost never have come across a bad diode-and this would affect (usually) only one, sometimes 2-3 notes depending on IC design.

 

if you do get spare rubber boot strips-from Keyboard Kountry or similar-make sure 1) these are an exact replacement and 2) are new-do not bother buying "pulls" or used-as these probably will hve the same malfunctions-I had to learn that the hard way.

 

One last word and i don't work for Casio-saying this as a musician-I have 4 Privias-of varying ages-all played on quite a bit-and so far I have had no malfunctions like this at all.  i always keep dust covers on or in cases-it is frustrating how many keyboard malfunctions are caused by-cr*** that gets into the key mechanism-the rubber boots are very sensitive and mostly stay very tightly sealed along the IC boards-but once you open these up do not clean that carbon with anything except compressed air and maybe a very lint-free damp cloth. Again, learned from experience.

 

Good luck, and post back, Am always interested in how these problems get solved-always recommend a tech first-and only DIY if you absolutely have to and not under warranty. I have tech training/repair, and still find certain repair problems impossible on my own. Keyboards are one of the most difficult electronics to repair IMO, short of working for NASA!

[Alvin]

Hello everyone. We have a Casio CDP-130 in our church that has many keys that are not working and I want to replace the conductive rubber but I couldn't find the exact type. Can anyone help me

where can I order the exact conductive rubber? Our church doesn't have enough money to buy a new piano. Hope there is somebody that can help us from this forum. Greatly appreciate your help. God Bless. - Alvin from Philippines

[PETERINTHAILAND]

I have a Casio AP 260 Celviano  piano with one duff key

it has a red 3  x3. Rubber plate on I take it there are conductors in the rubber that sit on the small circuit board below …….?  Which i missed so will have to dismantle again 

if this is not the problem is it reallyworth repairing as it cost about 700 pounds to buy 5 years ago and i can buy a pk piano for beginners fir 300 pounds  new  ???

in Thailand so would have to send a 12 hr journey to the capital Bangkok