I have a Kn1000 Technics keyboard. All the lights seems to be working. No sound now through the headphone jack or outputs in the back of the keyboard. Does this unit have a sound board?

try onscreen keyboard

The headphone jack on the computer connects to the sound card, a hardware device that controls audio input and output on the PC. The card contains a digital-to-analog converter that converts analog audio into digital signals and visa-versa. The performance of the headphone jack, therefore, depends on how well the sound card functions; if the card doesn't work, then the headphones connected to the PC won't output sound. Reconfiguring the audio settings will often fix problems with audio output on the headphone jack, but if the former fails to resolve the issue, replacing the sound card in its entirety is sometimes the only means of repair.
Click "Start." Enter "sound" into the search box. Select "Sound" from beneath Control Panel. Double-click "Headphones." If no "Headphones" option is available, double-click "Speakers." Click "Properties" on the General tab. Check the Device Status field for errors. Look up the message on Microsoft Support for more assistance, if applicable. Close the window if the Device Status field reads "This Device Is Working Properly." Go to the "Levels" tab. Click the speaker button to unmute the volume if the icon contains a red circle-backslash symbol. Drag the top slider to the right to increase the headphone volume. Go to the "Enhancements" tab. Check "Disable all Sound Effects." Go to Applications, and then clear "Allow Applications to Take Exclusive Control of This Device." Click "OK" to close Headphones Properties or Speakers Properties. Test the audio. If the headphones fail to output sound, unplug the headphones from the computer. Reconnect the headphones to the PC. Headphone jacks are color-coded lime green on most PCs. Look for the headphones symbol if the jacks are not color-coded. Plug the headphones into the line-out port on the back of the computer if the headphone jack on the front of the PC fails to work, or visa-versa. Test the headphones. If headphones still won't emit sound, the sound card most likely requires replacement. b> Replacing the Sound Card b> Shut down the computer. Remove the power cord from the back of the PC. Disconnect the keyboard, mouse, monitor and all other peripheral devices. Loosen the screws found on the back of the case, then slide the cover panel off of the case. Touch the chassis to protect the hardware from electrostatic discharge, or ESD. Set the computer on its side. Locate the sound card found on the opposite of the audio jacks and loosen the screw that secures the card to the computer. If no expansion card is located opposite the jacks, the computer uses an integrated sound card which can't be removed. Remove the new audio card from its protective packaging. Line up the card with an available expansion slot on the motherboard, then push the card down into the slot to install the new audio jacks. Screw the card to the computer case. Reassemble the computer. Turn on the PC. Boot in to Windows and insert the CD that came with the new expansion card. Follow the onscreen instructions to install the sound card software to the computer. Plug the headphones into the new line-out jack. Hope this helps.

Please plug/ connect this wireless headphone base unit in Line Out jacks at back of amplifier to get sound in headphone and turn down amplifier volume control to shut off its speaker sound.
Thanks.

Check if headphone jack also has right channel dead... If headphones work on both channels, switch contacts on headphone jack MIGHT be the problem.

GET NEW RCA JACKS

Ensoniq zr-76 no output signal on the main and aux, but i have output on headphone jack?

please bring a good contact cleaner from radio shack near you and apply the spray over the socket of the headphone(the place where you put your headphone jack)take headphone jack out and apply spray in and insert the jack in and out many times.-also check your system setup and confirm that all speaker are on- no mute button pressed-no cable is disconnected.

Plugging headphones into the computer will disable sound output from the sound card by design.

Sometimes you need to "burn in" your headphones. Used headphones usually produce a better sound than new ones. Simply let it play some music continuously. I usually burn in my headphones with some AM/FM static. After a while, the sound should improve. Good luck!