[Radio Wrangler]

Setting your pot to too high a resistance value does not park the output at max volts.

The current coming out of the 'adj' pin is what powers the voltage reference and regulation amplifier inside the chip. Rob it of this minimum current, and the reg shuts down. If you're unlucky, it may go silly for a moment.

Note the diode reverse-connected across the reg. If the input gets shorted by some fault elsewhere, this protects the reg from being destroyed by the charge stored in the output cap. That datasheet diagram shows 1N4002 which is fast enough. The board is marked 1N4007 which, I found out a long time ago, isn't always fast enough. The 1N400x diodes aren't just different grades of the same thing. The higher voltage ones are totally different designs and are glacially slow. They aren't PN diodes, they are PIN diodes. They even make lousy rectifiers giving a burst of RF noise every time they turn off. They can dominate the noise of a switch-mode PSU!

Note that your circuit, if the pot slider skips while moving, will give a burst of max output before the reg shuts down. This may destroy whatever you are powering if it can't take the full output voltage.

David