White Keys louder than black keys on Privia PX-850

[mik pointe]

I bought a used PX-850 for a truly massive discount, so tried it out quickly.  Upon playing at home, I noticed most of the white keys are very much louder than the black keys. The black keys have a soft pianistic feel at key bottom. The white keys clanky. Anybody have any experience with this? Wondering if it could be felt or if perhaps something else that is the trouble :)

[Jokeyman123]

I think you found out why it was massively discounted-it is massively defective. Sounds like the felt cushions are messed up pretty badly which are under and over the keys-there are typically 2 rows of felt-one on top to quiet the rebound, and one at bottom when hitting downstrokes. If the cushions are badly worn-it may be affecting the length (depth) of the key throw-which in turn will change the dynamic response. And it could be that the structure that holds the fulcrum arms in position is out of wack or broken, so the hammers are not operating properly in relation to the key action. Something is grossly wrong here, and unless you know a good keyboard tech (or are one) this sounds like it needs some major work to get it right. Can you return it, either to Casio or the vendor who sold it to you? This is definitely not a typical Casio Privia key action.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[mik pointe]

On 5/26/2018 at 8:22 PM, Jokeyman123 said:

Thank you very much, Jokeyman!  It's nice to hear from ya here... I actually perused your detailed and helpful post about felt.  I bought it for group classes on the premise that the headphone jacks were broken, and it turns out they work fine, but there's this problem.  To test it, I tried reinforcing the top felt (where the imitation hammer hits the top where the strings would be on a grand).  It seemed to help a little but not totally for the amount of padding I stuffed in there. Going to investigate the other felt, and see if something is loose too.  Really appreciate your post :)   

 

[mik pointe]

On 5/26/2018 at 8:22 PM, Jokeyman123 said:

"I think you found out why it was massively discounted-it is massively defective. Sounds like the felt cushions are messed up pretty badly which are under and over the keys-there are typically 2 rows of felt-one on top to quiet the rebound, and one at bottom when hitting downstrokes. If the cushions are badly worn-it may be affecting the length (depth) of the key throw-which in turn will change the dynamic response. And it could be that the structure that holds the fulcrum arms in position is out of wack or broken, so the hammers are not operating properly in relation to the key action. Something is grossly wrong here, and unless you know a good keyboard tech (or are one) this sounds like it needs some major work to get it right. Can you return it, either to Casio or the vendor who sold it to you? This is definitely not a typical Casio Privia key action."

 

 

 

 

 

 

 

 

 

 

 

 

 

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After further tests, I think it is the black keys aren't getting to full velocity.  I plugged into MIDI and played the hell out of them, literally with fist, and the black keys would not get to max.  White keys got to max similar to what you'd expect (no fist needed).  Upon disassembly I noticed the black keys fall onto raised rubber platforms to keep them higher than the white keys.  I wonder if somehow these uniformly got altered.  I also wonder if it's somehow related to the brains of the machine.  The tri-sensor contacts all looked similar - no evidence of dust or gunky dried soda or other things I've found in velocity-wrecked keyboards. The felt also looks to be similar.  It's got to be either something stopping the black keys from hitting before they get to the bottom, or some hardware issue that for some reason is controlling only non-natural keys.  It's exciting to learn. Calling support tomorrow :D. Any genius thoughts welcome!  Starting to think the weights were put on wrong for the black and white keys.

[mik pointe]

Update to everyone.  Thanks for chiming in.   With patience, I nabbed a px-150 for $150 .  I took out the entire keybed, swapped it into the Px-850 and the 850 works perfectly now!!!  

 

Before the key action swap, I had ruled out - the keys, any felt issues, and I think the contacts.   Now, I have a px-150 with the same problem but I intend to keep tinkering until I figure out what on earth is going on.  All told I learned a heck of a lot, especially that the key actions in px 150 , 350, and 850 are 100 percent swappable IF You are a de facto tech.  The lay person has no chance with this operation. 

 

 

[mik pointe]

I solved this issue.  It took a lot of exploration.  For anybody else pulling their hair out over this issue... 

 

There a tri sensor rubber contact - the one towards the front seems to control high velocity in a sense, even though it's the time between the strikes of the different sensors that calculates the velocity methinks.  The bottom of the black and white keys, as well as the black and white keys' rubber contacts are different from each other by design.  In my unit, the angle of the rubber contact pcb was such that the white keys were striking the front contact pad too late, causing them all to sound unnaturally loud (hitting the other sensors too soon after, thus tricking it into thinking I was playing louder).  I was able to correct the angle by literally putting VERY thin carboard as washers, under the screws that hold the Rubber Key PCB to the rest of the keyboard, thus changing the angle so that the keys weren't hitting the front pad at the wrong time.    The result is that the keyboard plays correctly now!!!!!   This is a picture of the difference that the cardboard made.  In a perfect world, one could use washers that were the right size.  I imagine that this is a factory defect, as I've come across a few folks that have had this issue.  This works because the black keys rest closer to the pads than do the white keys (even on a properly functioning Privia).  So, my adjustment didn't make any noticeable difference to the black key sound, only the white keys.

In the Photo, there are two PCBs visible.  The rubber contacts themselves are held by three of these.  The further one is corrected to be at the right angle.  You can see the tiny difference.  But really, it plays like my other Privia that didn't have this problem.  This was the most maddening keyboard issue I've encountered yet. It works now though

Warning: If you use a material too thick, the key won't work at all or will cut off abruptly.  Start small and work up.  I got lucky on my first try, by comparing it to a youtube video of Privia 850 action from the side.

 

[Brad Saucier]

Thanks for the update.  I'll keep it in mind for anyone else who might have the same issue.  

[mik pointe]

On 8/1/2018 at 12:19 AM, Brad Saucier said:

Thanks for the update.  I'll keep it in mind for anyone else who might have the same issue.  

Sure thing, and thanks too.  I updated it to reflect that it's the time between sensor hits that determines velocity - not the force per say.  Have a nice day

[Jokeyman123]

Wow-that took work! Who would have thought this possible? But then, I just modded my PX560 to quiet the keys a bit and it wasn't what I expected.  And yes, velocity (dynamic)  range is determined by time comparisons between sensor contacts. Think about this repair-the difference in depth or length of individual sensors is actually apparent only internally with all the keys I've worked on-the outer boots look the same, the inner carbon contacts are different sizes almost completely undetectable without looking extremely closely, another excruciating fact learned from experience. Not sure about the Casios, haven' torn them apart that deeply. Thanks for posting.