Hi @chanozga,

Like the answer above asks, do you get any audio from the headphone socket?

If you do then there may be a problem with the headphone socket not connecting the speakers back to the power amp when the headphones are removed from the socket.

Here’s an image taken from the service manual which shows how the headphones’ socket has contacts that break the circuit to the speakers when the headphones are inserted.

(click on image to enlarge for better viewing)

If there is no audio at the headphone socket either, then here is a link to the service manual for the keyboard. Like most service manuals it has a full schematic circuit of the keyboard and a parts list which should enable you to find and fix the problem

To download the manual, click on the link above and then click on the “I am not a robot Captcha” checkbox below the Document preview box. Pass the test and then click on Go to Download. When the sentence changes from This file is downloadable free of charge (5/day): ...processing... to This file is downloadable free of charge (5/day): Download(yamaha psr-450 sm) click on Download. Be patient as it takes a little while to find the file.