Hello, I have a Yamaha P90. 4 keys are not responding. all others are ok and give sound. What happened ?

Seems the carbon layer under the button needs repair.

first, how old is this unit? according to this page https://en.wikipedia.org/wiki/List_of_Yamaha_products#Electone_(electronic_organs) they were built between 1983-1988. In other words, it's over 30 yrs old and it may have had some internal electronics finally die.

https://www.manualslib.com/manual/779640/Yamaha-Electone-Fs-30.html

https://www.manualslib.com/manual/779640/Yamaha-Electone-Fs-30.html?page=29#manual

Just a shot in the dark but a lot of keyboards allow for splitting the keyboard in half or even in quarters to assign multiple sounds... have you tried a total reset? Or explore the manual for setting up a split keyboard. Might help.

Hi
In terms of no electrical power it could be either a faulty power adaptor, broken socket. However the feedback with batteries could indicate a more serious fault. If the batteries are know to be good try a reset. Hold down the highest sounding key while turning the keyboard on. Release once you have lights or a display on screen. Has the noise stopped? If so then try electrical connection again, if still no power ensure you are using the correct power adaptor and see if it works if you wobble the connector - they break away causing an intermittent fault. Report back and maybe I can offer more advice depending on how you progress with the above.

Dan
Becketts Music Ltd

1) Try a partial reset by holding down the last white key while turning the unit ON.
2) If you haven't recorded any performance(s), for a full reset, hold down on the last white key AND THE lst three black keys while turning the unit ON.

It is a lot of work to open and access the key contacts. Here is your service manual:

http://elektrotanya.com/yamaha_dgx-620_ypg-625.pdf/download.html

Scroll down to "get manual" and click on it to download. Ignore other download links on the page as they are for viewers and other software.

Hi, i think you can. You can go to any of the Yamaha companies around you area and explain to them the problem of the keyboard. They will give you good and quality replacement part for your Keyboard.

Make sure you go to only Yamaha company to avoid getting a wrong part for your Keyboard.Avoid road siderepairsforissue like this,it's more complicated to handle

I guess that will do.

Thanks for using fixya...

Yes. You will need to have a MIDI interface on your OC and also select in the sounds control panel of windows that you are using the external synth. The MIDI will expect the PSR to respond to the "general MIDI" assignments.

from what you say the humming is caused by large capasister which maybe leaking so could well be a power supply falt
or mabe dry wire
o/c on audio maybe
you need engineer freind

I'm sorry but it sounds like you will have to have it repaired professionally.