KORG LP-350 Digital Piano Low Volume

[loyukfai]

Hi there, I have a Korg LP-350 which has similar issues. Both the speaker and headphones output is very low and there is crackling.

I've a multimeter and the voltage output from the adapter is right at 12V.

Where can I start troubleshooting?

Thanks!

Reference: https://www.manualslib.com/manual/1331773/Korg-Lp-350.htm