KORG C-303- power doesn't always connect or cycles off and on

The buttons are damaged or defective. Replacement may be the only answer.

This is the help that the owner manual offers...completely useless.
However, it is likely that if your piano isn't turning on, either your connection is bust or your AC power adapter is broken. You can purchase a replacement relatively cheaply. https://www.thomann.de/gb/korg_netzteil_ka_320.htm

It is asking for confirmation that you want to initialize the unit. The manual doesn't say anything about this... but you should try pressing the "Yes" button to confirm you want to initiallize the unit or press no if you want to staart without initializing.

Some of these are easy to get the batteries in backward. Also see if the soldering of the battery contacts may have broken loose.

1. Power-off the PS60.
2. While holding down the four PERFORMANCE buttons and the OCTAVE DOWN button, power- on the PS60. The PS60 will be initialized, and the factory-set data will be written into internal memory. The display will indicate "Initializing..." while data is being written. Never turn off the power while this indication is shown.

Manual available here:
http://www.korg.co.uk/downloads/ps60/docs/PS60_OM_E1.pdf

First thing... make sure you are using the KA320 power adapter with it. We will work from there.

The unit probably is sensing an error of some type. Check these things: That NO key or button is STUCK down. Next, one could try reseating the memory sticks if you have expanded memory.

Let me know if you find a button or key is stuck down (not uncommon when unit has been wrapped) or you are using the wrong power adapter.

From the user manual troubleshooting:

No sound

• Are the other devices or headphones connected

correctly?

Check the connections. ........................................ (see p.6)

• Is the power of your amp or mixer turned on?

• Is the [MASTER LEVEL] knob raised?

• Is the Global mode Group 4 "MIDI Local" parameter

turned On?

Check the setting of this parameter.

• Are the bars of Drawbar 1 or 2 pulled out?
Pull out some of the bars.

Also check out this site and scroll down and do the "Factory reset" by holding down the buttons they say... AND please note that you have to hold them for a while during this.

A demo on YouTube shows the owner pressing one of the buttons on the left side to select possibly a bank as well as the start.. I could NOT find a manual online to download.

Assuming the C-303 has a MIDI out, connect a MIDI cable from the MIDI output of the C-303 to the MIDI input of the symphony module.

Connect two audio cables (mono 1/4 inch) from the symphony module to a suitable audio amplification system OR possibly into auxilary audio input jacks of the C-303, if they exist.

I have a Symphony module but not the piano you have and I have mine connected to a Yamaha organ.