Fixing loud key on PX-850

[duinsel]

Hi,

 

My Privia PX-850 developed a loud key (i.e. full volume regardless of the key actuation force). I suspected an issue in the sensor of the key, and opened up the piano to try and repair the issue. I could not find nice information online on disassembly of this piano, so I'd like to share some pictures with you here, perhaps it will be of use to someone.

I started by removing the backpanel. That was easy, but be aware of the cable connecting the lid sensor. There is a connector that allows disconnection.

 

Next I removed the keyboard cover. A screw holds the metal bar in place on the spring mechanism. Loosen the screw and slide out the bar. Next, the whole cover can be slid out of the rails.

 

Next, I removed the whole keyboard assembly out of the cabinet. In retrospect than may not be necessary to remove the pianokeys and access the sensors, but this is how I did it. I loosened the center electronics cabinet and loosened all connectors. The high density flat cable can be unlocked by lifting up the plastic top ridge in the pcb connector. The right speaker casing also needed to be removed as it covers some screws.

 

I removed the front panel with the controls. It is attached to the keyboard assembly through several posts, unscrew these from the front panel. Also, At 1/3 of the length next to the grille two screws keep together two segments. After detaching, both halves easily come out. I removed the tape and ziptie connecing the cables to the white keyboard assembly.

The keyboard came loose with 3 screws on top and a whole bunch on the bottom. After this, the whole assemble could be maneuvered out of the back with relative easy. Take care to support it well over the length.

Next, I loosened the retaining bracket behind the affected keys. Also, the black posts for the front panel had to be removed in that segment. After removal, I could take out first the white keys, then the black. The keys hinge between white plastic tabs, after prying and spreading them a bit the key can pop up, and move back and out. I removed keys until a whole sensor segment was exposed..

I loosened the rubber strip from the membrane switch array gently. It is stuck in with soft rubber pins in holes on the pcb.

Each key had 3 contracts (tri sensor!) at different heights, I suspect the connect sequentially and stroke force is deduced from the timing between them.

Finally, what I came to do. I gently cleaned both the carbonized rubber contacts and the zigzag pcb segments with isopropyl alcohol and a sort of cotton tip applicator.

 

Then reassembly. The rubber segment was hard to get seated in the holes, until I found that a paper clip wire can poke in the holes on the top and nicely push in the 'legs' below in their holes. Next the keys went back in, secured by the brackets, everything back in the cabinet, and try to remember where all screws came from.

 

In the end, I powered up the instrument, and yay! the piano key is now touch sensitive again. Mission accomplished.

 

Over here I made a movie of the action being actuated.

 

 

[Brad Saucier]

Admin Note:  This post is marked as solution since this is the very first thing anyone should try.  If this fails, the rest of this topic may help. 

 

  Did you try blowing air in the gap around the key first?  It might have saved you a lot of work. With key malfunctions like this (from any brand) the first thing I always suggest is air. Believe it or not, that works most of the time.  No disassembly required.

[duinsel]

Hi BradMZ. Good point, but yes, I first tried to blow air (from a compressor, you can just see it on the second picture) between the gaps of the keys, that did not help. When I got the back panel off, I next tried to blow from below the keys, that did not help either. After that, I proceeded with disassembly.

 

However, the silicone rubber contact strip seem to be well sealed against the pcb (see the picture with the paperclip), I would have thought air could not reach the contact pads underneath that easily. But a good easy thing to try, as you say it sometimes works.

 

Two things to add to my post above. First, the piano was obviously out of warranty (purchased 2013, >4 yrs old). Second, there was no obvious fouling of the pads, nor something spilled. The picture I took is pre-cleaning. I did remove some dark residue by cleaning, but this was the same for the good keys and the bad key.

 

 

 

[BryanD]

Thanks for posting this.  Our PX850 developed a similar issue on the D key in the same area as you showed in the picture.  Your information helped me to open up the keyboard, clean and fix the issue.  I was hoping I would not have to remove all the screws holding down the keyboard but unfortunately had to in order to tilt the keys forward.

 

Not sure as to the cause of this issue.  Like you, I noticed that the board was not overly dirty but did remove some residue during cleaning.

 

[duinsel]

Hi, great you could fix it, and good to know that the post was helpful, that was the point after all!

Mine is still going strong, fingers crossed.

[mik pointe]

The white keys on mine are all labeled 21.  a21 b21 c21 etc.    I'm curious were all of your white keys labeled 22? I see in the middle they are.  Thanks!

[duinsel]

Hi Mik,

I honestly don't recall. Maybe a different hardware revision?

I only took apart the center key block containing the defective one, no preventive maintenance on the rest. No new defects have appeared in the mean time.

[jeffn1]

Thank you!  This is great.  Unfortunately, I have had this issue with several Privias (PX-160's and earlier).  And I think it is time consuming for keyboard repair places to do, so they say it is not worth it.

 

If videos could be posted for other models (PX-160), maybe I would try to fix the problem key on the keyboard (sometimes improperly get full velocity on a key).  But, of course I will try compressed air first.

 

If anyone has links for other models (PX-160, PX-350), I would appreciate including the link(s).

[Jokeyman123]

Look for my posts under the PX350 category-I've posted a few pictures of my disassembly procedures for that keyboard when I upgraded the felt bumper strips.

[jeffn1]

On 9/26/2018 at 6:19 PM, Jokeyman123 said:

Look for my posts under the PX350 category-I've posted a few pictures of my disassembly procedures for that keyboard when I upgraded the felt bumper strips.

 

Thanks!

[Dave March]

A thousand thanks, this helped me fix my PX-350M !

 

Different case arrangement, but same keys, rubber strips, and circuit board beneath.

Was sitting in its box in a closet for over a year till I saw your video and decided to try your method. AND IT WORKED !!

 

 

[jdube]

This was extraordinary. Was able to fix a loud key on my PX-160 with these helpful photos and descriptions!! Thank you!!!!

[Matt Lee]

I have a Privia px-800 and I’ve removed the bar, but the cover won’t slide out down the rails. What should I do? 

[Manuelm106]

I had the same problem,so I decided to turn the whole thing apart . Different model but same arrangement of keys. I dismantled all ALL the keys and unbolted all the screws, until I got down to the main board of the piano. I identified the problematic key (D, 15th or so from left to right). When the key was played, all the others around it would have a random loud tone. I found the sensor for that problematic key and guess what? Over it was some kind of dirt, like a dry stain of liquid, probably from a spill. I link a picture of something similar. I proceeded to clean it, tested and worked perfectly!

I actually enjoyed the process of dismantling the piano and understanding the issue, fixing it and put it back together.

In short, the solution is simple, but it takes time, patience and care t get to where you can apply it

I hope this post helps

https://photos.app.goo.gl/2wnkaZkfnAW9e9426

https://photos.app.goo.gl/hsJj6BzFKXx6rHH59

 

[HenryNG]

duinsel, you are an absolute lifesaver! I was dreading trying to get my PX-160 fixed or having to replace it, but nervous to take it apart and potentially make it worse. Well, I dreaded so long that my warranty ran out and I figured "Might as well." Perfect! I couldn't believe it when my key (F4, for what it's worth) played beautifully. I almost cried. Thank you!!!!

[Harty105]

Thks Duinsel ... even today your thread helps even me today on my purchased PX-850 as I need to sort out some rattling keys after a recent 2nd hand purchase for our local school.

 

One thing may I point out is your last video picture ... the bottom left cushioning strip seems to be on the wrong side of the plastic shelf as per the Casio parts service manual .. your video shows the strip as being under the plastic shelf when it should be on the top (look closely at the bottom left of your vid capture on pause) .. it may be just the way the vid was taken ?

 

There are 4 cushioning strips on the Privia keyboard main frame ... 2 top (back and front) and 2 bottom (back and front)

part number 66 front bottom (thin) cushions the larger downward fin of the white key (back of the U shape)

67 front top (thin) ... this one looks like it is in the wrong position but it should cushion the front bottom lip (front of the U shape)

68 rear top (medium) looks like a white licorice allsort strip just at the back top of the key action ... and

69 front bottom (large) cushions the rear of the hammer action

 

I am waiting for the parts to arrive but have also bought some draught strip, some furniture cushioning strip and extra 3m double tape off Amazon just in case I can do same with that. Time will tell.

 

Luckily i also have a PX-760 in my other school where we teach and the parts are exactly the same and the whole keyboard layout is also the same but the part numbers are different .. nrs 56/57/58/59. This is worth knowing as the PX-760 is still being sold whereas the PX-850 is discontinued.

Hope this helps

 

[duinsel]

Whoop, I did it again...

Another key on my piano failed in the same way as the other key 5 yrs ago.
I have proceeded to fix this key in the same way as before, but figured out that some of the steps I took last time around are not strictly required, so I was done quicker and easier this time around.  Again, I thought it would be useful to share (and I was happy to read that other users found my previous post useful, thanks for leaving a comment!)

As before, I started by taking out the hinged lid, the back/top panel and the sliding keyboard cover.

 

Next, I disconnected the flex cable to the control panel, and removed the center segment holding all controls. The side segments I left connected (solder joints to the speaker elements...).

Different than last time, I left the plastic keyboard assembly inside the wooden cabinet, that saves a bunch of hassle and reduces chances of accidental damage. It is necessary to undo the screws that hold it in though, as we need to shift the assembly a bit before we can remove the keys.
I undid the silver screws on the inside that hold the assembly on the wood case, and then also the silver screws on the bottom of the cabinet that do the same. I did not need to remove the electronics box on the bottom, but I have a feeling I forgot to put a screw back in located under that box last time, so maybe others need to remove that box for access to these screws.

 

Once the keyboard assembly is loose it can slide back a cm or so, be careful for the wires going through the bottom panel. Undo the brackets near the hinges of the keys, once free a white key can be pried out at the hinge, and when white is out the blacks can come out as well.

 

I put the keys aside in the order they came out to help reassemble.

Now I had access to the sensor PCB, I chose to remove the three center sensor strips (which included the sensor of my bad key). The contact area on the PCB was cleaned with alcohol, and the silicone rubber contactor strips as well. After drying, assembly was the reverse procedure, a paperclip is still a lifesaver for getting the rubber pins back into the PCB. 

 

Fortunately, after assembly the faulty key was fixed, and could be played soft or loud as desired.😅
Let's see if it will last another 5 years like this.

[Chuck Norris]

Thanks so much. Just fixed two keys on our PX-850 (one loud, one not working)

Taking it apart and cleaning did the trick.

I never disconnected any of the cables except for the back cover clip. This way I could plug in and test every step of the way...

Thanks again

[andyobl]

Brilliant. Managed to fix ours with this guide. Wife is chuffed to bits . 

[MattBob]

Hi, thanks for the instructions duinsel. I have just fixed my PX-850 with your help! 🙂

[Harty105]

This is an amazing help - just wish it was in video clips to put words to the actual parts and process into an action to quantify what you mean - especially for someone like me.

 

I have an 850 with this problem now and will swop it out from my wife's school and replace it with an Ap260 and then try repair it with cleaning alcohol/swabs etc. Just hope Casio parts UK still are helpful - the ongoing problem for us all in this throw away society is when is the time to discard and who to? - cant just leave it by the roadside although some people no doubt do down country lanes. Thats another story.

 

Things can be fixed and Casio/Roland/Yamaha etc should think about that for owners who dabble in DIY and make things easier but moreover .. make a service book for each model that is easily available (even self repair Vid's) iso just a user manual that no one really wants after a week or 2 ... or better still put the 2 together. 

 

I was given a list of repair people here in the UK and there are about 8 in a 100 mile radius to us but all have either retired, left the biz or moved or WILL NOT offer callout for my distance (nor drop off!!!) - how does that work?, not very customer friendly at all.... so who can one call to help. Even casio Uk do not offer repairs unless it is a warranty issue.

[NearMe]

I've just fixed a loud key on my PX-850 using instructions in this thread, so thank you to all who posted. It looked like it's a popular issue with the PX-850?

 

FWIW, I almost broke my white key when trying to put them back. You can'tjust  press it down in the reversed way of how you pry it up. It needs to be slided from the front, engaged the hammer first, and then the top of the key (where it is attached to the hinge) should be snapped into place at the end.

[Joe Muscara]

20 hours ago, NearMe said:

It looked like it's a popular issue with the PX-850?

Dirty key contacts happen with a lot of keyboards. It seems to depend on a number of factors. I've not had it happen very much, while others have.

[kschoonm]

This was very helpful to me.  I have a PX-850, so of course, these instructions were 100% applicable. I had issues on 3 keys. All counting from the left: Key #13 (A), Key #34 (G-flat), and Key #35 (G). The A key was a loud note issue no matter how softly the key was pressed and the G keys had a very loud buzzing sound. All 3 key issues were addressed by this procedure. Important comment on potential simplification for this procedure: in addition to not needing to remove the keyboard from the piano,  for removing the back panel and the panel with control buttons/dials, just using a piano bench or something similar on the back side allows you to set those components on so that you don't have to disconnect any of those circuit board connections either. This allowed me to have a fully functioning piano all during the disassembly process, which made it so that I could test whether the fix worked before I put it all back together.  I now have a piano that is 10+years old that works good as new now.  Thanks!

[Mark Aaron James]

Adding to the choir of thank yous. This worked for me as well, and I'm back to having a fully functioning board. Also not afraid to go into again if need be, thanks to the images, and results.