How do I unlayer notes on my casio privia 150 digital piano

SOURCE: I have a Casio Privia PX-320. The left side keys

Check that the front of the keys is not hitting the lower plastic case front. If they hit it, then you need to disassemble the case partly and see what has shifted. It is ALSO possible that something has caaaused the aftertouch sensor to move out of position and it is hitting the keys early. ANY of these conditions needs to be addressed before damage is done.

SOURCE: casio privia key issue

The only way to analyze this is to open the case. You may find contaminating material has gotten in, or broken part, or key slightly out of position on pivots or pivot plastic broken.

When opening, be VERY careful of the tender ribbon cables. Have a large work surface that you can unfold the top onto. Be careful to use correct screw lengths and thread in each place you removed.

SOURCE: Casio Privia PX-130, 8 months old: fluttering sound

If I were to venture an educated guess I would vote for failing filter caps in the power supply.

The power is likely collapsing under load of the speakers but headphones take much less drive.

If this has an external wall-wart power supply, you might try a new one IF the output is found to be under the rated voltage.

Internal power supply components are beyond those individuals that are not adept at electronics.

SOURCE: I have a Casio Privia

Beofore you replace it, if it is only scratchy give it a good working by sliding it back and forth a rew dozen times. (if it is a slider type) If you can get some electrical contact cleaner with a thin plastic tube, try squirting that into it and work it again, if that fails, then look at the volume control replacement.

SOURCE: I've recently purchased a Roland

Sorry, but Roland uses the opposite sense switch. They use normally closed where Casio requires normally open contacts. SOMETIMES one can rewire the pedal internally, but you have to be mechanically and electrically inclined to do that.