Question What is wrong with my power supply? Incorrect DC output on 5v rail.

Hello, I have this power supply for breadboards. http://wiki.sunfounder.cc/index.php?title=How_to_use_YwRobot_Power_Supply_Properly More: https://protosupplies.com/product/ywrobot-breadboard-power-supply/

I plugged in a 12v wall adapter as instructed. I plugged in a battery charger into the USB port (no battery connected thank god) and probed the output of the charger, which fluctuated oddly between 3.7v and 5v. Then I noticed the adapters light flickered, went out, and the adapter started smoking and the plastic started melting. I immediatly turned the psu off and unplugged it.

The battery charger is toast. The power supply seems unharmed.

I probed the output of the USB port. It was over 15V! The input voltage to this power supply is only 12v.
I probed the output set to 5v. It was at 15v. I set the output to 3.3v, and it went to 3.3v. I turned the output off, and it went to 0v.

Am I using this wrong?
 

TJ Hooker

Titan
Ambassador
What 12V adapter did you use? Did you see this note? "Note: 12V is the voltage limit. If you use an AD-DC adapter, you're recommended to use 9V in case of unsteady voltage which may burn the board. "

What voltage do you measure from the 12V adapter output? Try measuring DC and AC.
 
Well, I best leave it off. One output of the 5v regulator goes to the input of the 3.3v regulator and the other to the 5v output.

One output of the 3v regulator goes directly to the 3v output. The other gets passed through a current limiting resistor and fuels the power LED.

Throwing 15v into the imput of a 3v regulator with a 12v max input hasn't fried it yet somehow.

I figured this out with just a multimeter. And gogle.
 
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