Top view of the Sony SRS XP500 speaker, showing the -Power- button.
When the Powerbutton on your Sony SRS XP500 karaoke speaker is not working, this likely means one or more things as follows.
Sony SRS XP500 Power Button Not Working: Reasons Why
Dead Battery. The internal battery is empty needs a recharge for continued speaker operation. Use a widely available AC power cable to do this.
Faulty AC Cable. The power supply is built into this speaker. So externally, there’s just an AC “cheater” cord that supplies 76 watts to the speaker. This cord may be defective.
Faulty Power Port. The AC input port for charging the speaker may be bent, corroded, or otherwise damaged, an sometimes seen on this model. So replace this if you have the necessary skills.
Bad Battery. That battery no longer recharges due to extreme age, repeatedly overcharging, very long storage, or heavy use. You may be able to obtain a replacement battery from Sony.
Dirty Button Panel. The button panel has sand, dirt, or other debris preventing the Powerbutton from making decent contact when you press it. For this, you can, if so skilled, clean the switches by disassembling the speaker, and blowing or brushing out the contact area.
Button Panel Has Failed. The switch panel is defective, and the solution here is to replace it. These parts are often available on eBay.
Faulty Speaker. Finally, your speaker could be broken beyond repair. If you determine this, then the best bet is just to get a new speaker.
The rear view of the Sony SRS XP500 speaker, showing it connected to AC power.