How to factory reset

SOURCE: Casio WK 1600 : Sustained keys

Remove all power sources for at least 2 minutes. That means removing the batteries and power cord completely from the K board. Then try again. If that doesn't do it, it'll be time for a service visit...accordianman

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 PX-800: When using the sustain

Check if the cble frm the pedal MIGHT be flexing or pulling on the keyboard case when you use it. Such movement COULD vibrate the power connector causing your problem.

Make sure you have the right power supply for the unit as one with too large a hole for the power pin would be intermittent like this.

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.