RCA AH5 AC/DC adapter switch polarity question
You are correct. The switch position shown has negative at tip of jack and positive on the sleeve. Most devices would use positive at jack.

Note that you have it on 12 V setting and this could be frying your devices even at the right polarity. Furthermore, there may be very poor voltage regulation in the device so that the 12 V becomes 16 V if lightly loaded. I would only use this for non-electronic devices such as devices with motors or lamps. For anything electronic I would use a regulated power supply.

Standardise all your connectors to "tip +" if you can for safety.

Nice tablecloth!