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


puslar123

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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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  • 2 months later...

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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  • 1 year later...

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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  • 3 months later...
  • 1 month later...

Thank you very much. i have one bad key, and didn't know until recently that there were single strips and double strips. I replaced the single and of course nothing happened. Your pictures are very helpful as CAsio support is not (except for one nice supervisor I talked to). I'm ready to disassemble.

 

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Fantastic bit of work. You went deeper than i did with my PX350 (disassembled for different reason)

 

 In case you didn't know-whenever there are 2 contacts together as you discovered, these control key velocity response in a very "touchy" and precise way, and this is the reason so many have trouble with suddenly loud or too soft keys, or no velocity response at all.

 

These 2 contacts are ever so slightly at different sizes (heights) not sure of this Casio- at least with all the keyboards I have repaired-you have to look very carefully to see this. The velocity is calculated by the difference in time between the key contacting first the one, then the other! So if either one of these contacts is even slightly off- there goes your velocity response. What surprises me is that the Casio has separate single contacts for all the keys, plus the dual contact strips which were the defective ones. Every keyboard I've repaired (not Casio) only had the 2 contact design exclusively-Roland, Edirol, Ensoniq, Generalmusic, Yamaha and Korg all used this design and of course with a non-velocity response keyboard, only the single contact which many brands use.

 

I think the Casio design may be better since it uses three contact points for the keys which must give the keys an extra cushion and insures there will be a working key (I think!) If the dual-contact design fails on other brands as I have found, the keys fail completely. So thanks again for posting your very ambitious work, It helps me (I own 3 Casios) and I'm sure will help others here who may have Casios no longer under warranty.

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  • 1 year later...

Thanks again puslar123!! I had to scrounge like 4 more YouTube videos to figure it out , but was able to fix my PX-130 with the same issue.

 

For everyone else, here's a quick summary of the steps:

1) Remove wing screws to remove lift piano
2) remove bottom screws
remove cross bar, then cross bar holders
3) remove black side screws (3 on each side)
4) remove outer panel on each side
5) remove 5 screws on inner panel each side
6) remove inner panel
7) lift electronics board - disconnect 2 ribbons
8 ) remove 3 screws holding white frame with the keys
9) lift frame
10) unhinge each key (white first, then black because white holding in the blacks)
can push hammer past felt 
no need to remove each key
11) once all the keys are “un-hammered”, can access the green PCB board
12) remove small black screws on PCB
can lay plastic wrap on white frame to protect from the grease
13) lift green PCB board and place somewhere safely
14) remove the screws holding the tan PCB board
can remove ribbon here - this one is harder to put back in
15) lift the PCB board and access the “velocity” rubber pads
need 7 full pads + 4 for complete replacement. just get 8 for safety
16) replace the pads - they are directional so you must put them in the same direction or they will play at full volume
17) replace tan PCB board, replace screws
replace ribbon
18) etc.
19) can test keys before reinstalling case
20) re-install white frame, electronics panel, inner panels, outer panels, then rescrew the bottom
 

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  • 3 months later...

Thanks so much, puslar.  I've been having this problem on my PX-130 for quite a while and recently it had gotten much worse. The fix is pretty simple, but I would have had no idea what to replace or what parts to get if not for this post. Everything seems to be working well for me now. Thank you!

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  • 7 months later...

   Saludos, quisiera saber si pueden orientarme tras ver este mensaje ilustrativo, tengo un px110 y tuve un pequeño accidente que presionó muy fuerte el re de la primera octava, suena pero la tecla està màs baja que las restantes y claro la articulación es irregular, ¿ serà muy obvio lo que pueda tener y serà factible que pueda repararlo ?, igual inconveniente ocurrió con la última negra del extremo derecho, pero claro interrumpe mucho menos para tocar; gracias por vuestro tiempo.

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  • 2 months later...

I have the same issue with Casio PX-330BK as puslar123 described. Unfortunately, pacparts doesn't provide me an option to ship the order to Russia. I suspect it is a political issue.
Can anyone list the needed part (named on pacparts "Casio 91087274212 Rubber/Contact/AG2") on ebay so I can order it at a descent price? Or is there another option of how I can buy the needed part?

UPD: I've contacted pacparts and they tell me to click "paypal" button before "checkout" button. It seems like it is possible to retrieve the destination address directly from paypal account.

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