Technics RPDJ1200K / A

https://www.manualslib.com/manual/1138062/Technics-Sx-Kn1000.html
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Get a
Universal 1/8" to 1/4" Headphone Adapter

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.

Try searching on Google for JNTWorld.

Have a look at my tip on Headphones. Click my user name to find it.

Follow the link to my blog it explains how to replace the jack.
Real Life And Real Charts

check your local market

You can buy replacement plugs and solder them on. Make sure you take the old one to the store when you purchase the replacement. The next thing you need to do is figure out which wire goes to which part on the plug. You can us a volt ohm meter to test the old plug and see which color of wire or which color of wire insulation matches to which part of the plug. You can also try taking the foam pad off the left earpiece and look to see if you can get the speaker plate off the earpiece. Once off you can look to see which color goes wher. There will be another wire there that connects the right earpiece to the left one. Make sure you unscrew the shield from the plug and put it over the cord facing the correct direction before you solder the plug to the wiring. Screw it to the plug after. Hope this helps.