Review on 💡 SHNITPWR 30W Universal Power Supply - Adjustable Variable AC/DC Adapter with USB Port - 14 Tips - 3V-12V Converter by Cee Pouncy

I bought this to power an electric guitar tuner (Polytune Mini 3), it didn't work no matter what tuning I used on the adapter, there were too no instructions how to use the adapter. We also noticed that the box was missing an item (reverse polarity converter) so we ordered a replacement. Same problem, no reverse polarity converter so sent both back and ordered a regular 9V 1A power supply (center minus) and it worked right out of the box. The attached picture shows what it will look like when you receive the item. The second image is the missing part, copied from the ad.