Cuts out on me while playing

This link might help.

https://www.google.com/search?q=Casio+Privia+px-100%2C+loud+key

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The fact that ALL keys except G's and D flats are not working, points to a possible matrix or multiplexing problem.
As shown in the simplified schematic, if any traces (PCB tracks) from the mutiplexer / controller IC are broken, eg if the board has a crack, this could disable all identical notes for all octaves.
Otherwise the controller itself may have a fault.

(Some non-related info):
In reality, the synth's matrix is a bit more complicated than the basic sketch shown for explanation.
Diodes are included per key to prevent 'phantom note playing' and to isolate keys.
Velocity-sensing uses two set of contacts to sense timing from A to B contacts when key is struck.

It's possible to reset the DTXPRESS electronic drum kit to its factory default settings by performing a Factory Reset. Here's how you can do it:

Press and hold the [DRUM KIT] and [SAMPLE] buttons while turning on the power switch.
The display will show "FACTORY RESET OK?"
Press the [DRUM KIT] button to execute the factory reset.
The display will show "INITIALIZING" while the reset is being performed.
When the reset is complete, the display will show "COMPLETED".
Note: Performing a factory reset will delete all user kits, samples, and other custom settings that you have made. Be sure to save any custom kits or settings that you want to keep before performing the reset.

Hi, Could be a lot of different things.

Does it play through headphones?
If so this implies an amplifier issue.
Does it play when you press the demo button - if so it could be a keyboard issue.

Carry out a factory reset by holding down highest note whilst turning on. Watch screen does it report anything?

Let me know what it says and I will try and help.

My EWI 4000s started to play by its self making a loud low note and then it stop and now it won't play at all. I Reset to Factory Preset but that didn't help. What do I need to do to get it to play again?

You may need to do a factory reset. It sounds linke a transpose setting has been invoked. Read your manual under the word "transpose". A factory reset, if required, usually involves holding one or more buttons or keys down while turning on power and holding them until the reset is acknowledged.

It's probably your keyboard. Some keyboards are limited with it's polyponic capabilities. Some can play many notes at one time, some cut out when it reaches it's limits. Check your manual for specifications.

Have you tried connecting a single speaker to each output and cutting the volume down to see if you have a load or impedance problem? The amp may be perfectly fine except it's trying to play to a 2 ohm or less load :-)

Carl

My AP-620 has a pedal problem too... it sticks and I keep hearing the music I play ring out after the pedal is relaesed

This sounds like a power supply issue... Since the unit is new, make use of the warranty for repair or replacement.