Casio Privia DX-800 problem

Hi, I hope someone could shed some light on this problem. My Privia px800 boots up totally as normal. I get no sound from my speakers except if I put my ear right up against the speaker and hear a faint buzz when I press a key. There is also no sound from the headphone jack. However, the board works fine through midi as a controller board to control my midi software… absolutely no problems there. I want to have it work locally again and not sure where this points to, or what component may be the culprit… any ideas??

What about the other way round - can you send MIDI to the PX800?

Also - if you select a DEMO Tune - do they play through the speakers ?

Hello, thank you for asking. The board works completely as normal, but with no audio amplification for its internal speakers or headphone jack. I think its an amp problem. As I said earlier, if I hold my ear directly next to the speaker I can hear a faint buzz when a note is played (I can hear the instrument being played faintly under the buzz). If I change the voice, there is a variation in the buzz (and the new instrument can also be discerned under the buzz). which tells me that the tone generator part of the board is active. If my intuition is correct, it is in the preamp or power amp stage of the amplifier… does this make sense?

Got bad news for you - got my hand on a PX-800 Service Manual and found that the Line-out, Headphone and main speakers use separate amps (see pic) - the only common parts are Volume pot and the DAC on the main board.

MIDI in and MIDI out is served via main CPU directly.

Hence - look at maybe a faulty volume pot (they’re a little flimsy) and maybe cabling from main board to Jack board …

One more thing I just discovered:

The PSU has a 7812 chip providing the +12V only for analogue parts of the keyboard.

It’s common for the Line-out, headphone amps AND the DAC on the main board but NOT the main amp. If that chip goes - all will work except analogue sections.

Check that as well.

Thanks for your input… I like the power supply notion that you discussed… I’ll test that shortly…

Are any parts available like the Power supply circuit board (m409-psa) ?

or the Main pcb if needed?

Also, how can I get a full service manual for this board??

Let me know

thanks much
John