Most wall warts don't regulate good with little or no load but the real reason you can have problems with
the AMS1117 5.0 is the wall wart it's output to high even 12 volt is too high for some of them.
I never use any over 9 volt and haven't had any problems.
If it's going to be 12 volt on the input I use a lm7805

 

Seriously I’ve never had issues doing 3 day burn ins using the AMS 1117 5v on 12v running over 100mA and the SOT23 package works well on my tiny boards. I don’t think the protection is very robust on the Chinese chips. I might take apart the wall wart to see if I can figure out what happened to it. It’s strange perfect DC but too high and it’s a transformer. Maybe the primary developed a short. No idea yet.

 

Opened up the wall watt they don’t make them like this much anymore. Diodes are good and I don’t trust the cap reading but it’s fine. The coil resistance was a little high on one side. Primary and secondary has no short. 1.8 ohms vs 129. Yep looks like an internal short. I can save the bridge and cap for a bicycle dynamo project. Transformer is toast. Good thing I found the box of 12v switching supplies. Back in business. Thanks for bearing with me. Kind of boring but explorative. Would have been better if the caps pooped or something.

 

My board came in. Remind me never to use standard shipping. It only cost $7 but took about 3 weeks.

They do such a nice job on the boards.