My korg x5 keyboard only turns on but nothing comes out of the display.nothing is loaded and no characters displayed.

https://www.google.com search of the internet gives the following result:

https://www.sweetwater.com/sweetcare/articles/initialize-reset-preload-korg-x5-x5d-dr/

How to Initialize (reset), and preload on the Korg X5/X5D/DR

• Article #16230
• Updated on Apr 27, 2007 at 12:00 AM

Initialization: Hold Page + and Page - while turning it on.
Preload: Global Screen 5A, then select "OK".
ROM Check: Hold Edit and Global/Multi while turning it on.

How to Initialize (reset), and preload on the Korg X5/X5D/DR Initialization: Hold Page + and Page - while turning it on.

Preload: Global Screen 5A, then select "OK".

ROM Check: Hold Edit and Global/Multi while turning it on.

It's on this link-
How to Initialize reset and preload on the Korg X5 X5D DR SweetCare

I suggest a hard reboot / initialize. Istructions are in your manual or on the Korg website

That sounds like a manufacture date being flashed. Have you checked the battery? If you can't backup first, all your changes (custom sounds) will be lost, but that might be what you are looking at. Replace the battery, or have a service center do so. You'll want to reset after.

Try ROM check first.

Initialization: Hold Page + and Page - while turning it on.
Preload: Global Screen 5A, then select "OK".
ROM Check: Hold Edit and Global/Multi while turning it on.

Guide:
How to Initialize reset and preload on the Korg X5 X5D DR SweetCare

It is power supply regulator problem.
In the regulator circuit, DC 12volt from adapter is separated into +8V, -8V, +5VA, +5VD. Some causes when the unit hang /blank/ frozen is one of the existing supply voltage is drop. In general, +5V.
Also check the adapter voltage, if still normal and the current is sufficient.
Adapter must have DC12volt and current of at least 3 amperes.
It may happen, when the adapter is measured without load, it's read normal 12v, but when loaded to turn on the keyboard, many voltage decreases (lets say,between 8-10v).
This indicates that the adapter is not good and need to replace.

Have you tried it with batteries? Are you sure the power supply is working correctly? It should not need the OS to operate as a keyboard disconnected from the computer.

The cable connection is just a MIDI cable that uses opto-isolators so the 2 items are electrically isolated from each other. The software driver for the Korg should load without problem. The Korg program itself may be looking for inputs that are not there when the keyboard is off and the program itself reaches a stop command.

If the PA80 will not work on just the power supply- the power supply can be the fault- it has an internal fuse. Finding a similar supply with the same coaxial plug wired the same polarity is the way to test it if the battery option is not available.

NOT a fuse... thaat person knows nothing. There is something wrong for sure. Check if one of the buttons or keys MIGHT be stuck down (depressed). Sometimes the units check that all the control buttons are up and they don't really tell you why they fail to start. Beyond this a repair shop is in order.

You turn it on and there are the two buttons under the power on button. These ratchet the base frequency up and down. In the upper left corner of the display you will see what A is currently tuned to in tiny characters.

You can't always believe the display in regard to the model... Try finding the revision level display that will tell you what you have... It is NOT likely a seller would strip a X5D case to try to fool you.
Find what the difference is in the model and test your unit for that feature.