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[SOLVED] PX-135: some keys occasionally play at full volume

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Recently (~1 year ago) my fairly new PX-135 developed a nasty problem with a few keys (random: not the same octave, not next to each other). Specifically, if one hits one of these keys harder than a certain amount, it gets "stuck" at the highest volume (so touch response no longer works). The "fix" I found is to hit it even harder a few times in a row, and then it's back to "normal". This is not a purely electric issue - if I turn the piano off, wait, and turn it back on, the issue is still there. From the research I've done it looks like the culprit are the rubber contacts responsible for the velocity measurement (touch response). Because this is a recurrent issue, perhaps this is as simple as some dirt getting inside the contact and moving back and forth there, depending on how hard the key is hit.

 

I tried to get to the bottom of this by disassembling the piano. Unfortunately the keyboard  design is really bad: it looks like the only way to get to even one of these rubber contacts one has to remove one by one all the 88 keys, which is tricky. I tried, and removed some, but then accidently broke a part of a black key support, so it became wobbly (but still works), at which point I decided to stop, especially because I didn't have any replacement rubber pads.

 

I think I will attempt a disassembly one more time, because the problem drives me and especially my kids (who are learning to play piano) nuts, but this time I want to have some spare rubber contacts in case I need to replace some. I did find this spare parts store which apparently has some contacts for PX135:

 

http://www.pacparts.com/library/model.cfm?mfg=Casio&model_id=PX135WE&action=list_part&back=0

 

Does anyone know which of these are for velocity measurement? Also, can I buy somewhere the conductive paste/powder used inside the contacts (is it possible to replace it?) For exazmple, how about this repair kit:

 

http://www.oaktreevintage.com/parts/keyboard/casio_key_contact_repair_re-coat-kit.htm

 

Any other advice?

 

Thank you!

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Did you try blowing air between the keys? Sometimes that can dislodge whatever it is. 

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Thanks - I only tried with a hair drier, pointed right at the contact strip (with the keyboard partially disassembled)  - obviously not as strong flow as with an air can, and it didn't make any difference. I probably should try an air can.

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I just tried to blow air from an air can around one of the bad keys, no improvement. So no easy fix for me.

 

I've ordered a few contact strips from the link above, and will be disassembling the piano again when I receive them.

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Update (and success story!).

 

I finally got the replacement contact pads from PacParts (I ordered a few different kinds as I wasn't sure what I needed; it wasn't in stock, but I got it after one month; I ended up only needing the long double-padded stripes, which apparently measure velocity = loudness of key strokes: http://www.pacparts.com/part.cfm?sku=91087274212 )

 

Here is the disassembly of my Casio PX-135 piano. The most time consuming was removing all keys, one by one, using two small flat screw drivers, and (as far as I recall) removing white keys first. This is after removing all keys:

 

 

Casio Privia PX-135

 

 

Closer view of the problematic keys (marked with red). As you can see, no obvious issues here:

 

Casio Privia PX-135

 

 

Casio Privia PX-135

 

 

Next I removed the top layer of boards with single-padded contacts. (My test showed that these contacts are only responsible for the sustain feature, and have nothing to do with triggering a sound or its volume, so I knew they are not the culprits.)

 

Casio Privia PX-135

 

Close-up on a bad key: nothing suspicious here either:

 

Casio Privia PX-135

 

 

Finally when I removed the second layer of boards, I discovered stripes of double-padded contact stripes. I instantly saw the culprit: the key which I knew just got "stuck" at the highest volume had the corresponding double-padded contacts literally stuck in a pressed position. (Unfortunately I was so excited that I found the culprit that I forgot to take a picture of it.) Otherwise nothing obviously wrong with it - contact pads were clean and not worn out, no sticky stuff inside the pad. My only explanation is that perhaps these stripes are defective (may be too thin rubber; or perhaps wrong composition which deteriorated quickly).

 

The PacPart part which seemed to be identical was this one (Casio 91087274212; only 2$ each 12-key stripe): http://www.pacparts.com/part.cfm?sku=91087274212

 

It was very easy to replace the defective stripes (I had two stripes with bad keys): they are not glued or attached in any fashion to anything, they just lay in there. I lifted the bad stripes (grey colored), and put there the good ones (green colored, from PacPart):

 

Casio Privia PX-135

 

Casio Privia PX-135

 

 

After that my issue with stuck keys was gone.

 

If I knew what was the culprit in advance, I would have ordered replacement stripes for all the keys, because there is a good chance the rest are also defective which will eventually show. I will probably order the missing replacement stripes for the future, and if the problem returns I will replace the rest of them.

 

Dust couldn't possibly be the culprit here: the placement of the contact stripes is such (under double boards, and most importantly - with the contact pads facing down) that it is extremely unlikely for the dust to get there. (I am sure this is by design.) So my prior attempts to fix the issue using canned air were obviously doomed.

 

It's been one month since I fixed the piano, it was heavily used by me and my three kids, and everything seems to be perfectly fine.

 

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Yeah, sorry about that! At that time I just wanted something large and soft, and wasn't too worried about picture background :)

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Thank you very much for your helpful post. I have the same keyboard but only one key was affected. I purchased all 7 strips from PacPart, tore down the whole thing and replaced the strips. Piano plays like new again! I had been chasing this problem for over a year before I found your post. I'm guessing every Casio piano is built this way and this fix probably would work for 90% of these issues. Thanks again for your help!!

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I am glad my post helped other people!

 

An update - it's been more than a month since I fixed my issue, and the keyboard worked well all this time. Just in case I ordered more replacement contacts (to be able to completely switch to new contacts if needed), but so far the rest of the old pads worked fine.

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