Digging up the manual and promotional material showed a few things. They regularly refer to it as USB-C by name, and the manual lists the models as OBELIEVE OBL-0901500E / OBL-0901500B. I can’t find much on these, but they are manufactured by DongGuan, suggesting an off-the-shelf part.

IOW, the damage is unlikely to be from plugging in a standards-compliant USB-C PD adapter.

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What’s the model of radio, and if you have it, the official charger?

Does the device (actually, both devices- radio and charger) say it’s USB (logo, etc), or does it just look like a USB-C connector? Kenwood (now part of JVC) is pretty big. They’re unlikely to use the logo if not compliant.

Also, you mentioned plugging the display unit to power. Was that to an official charger, or to your own charger? Is it possible that your charger is bad? A lot of cheap, generic ones (anything from Amazon or AliExpress) can damage electronics.

It’s also entirely possible that your unit was defective before you even opened the box. Missing the charger means it probably wasn’t just unsold inventory.