Charge !

I finally did try the buck converter module mentioned before as a USB charger:

https://wb9kzy.blogspot.com/2025/04/buck-converter.html

It does seem to work, no smoke, the phone wasn't damaged, didn't hear any obvious electrical noise on the K2.  I did add a Schottky diode on the input to prevent polarity reversal and I rechecked the USB connector cable to make sure that it was wired correctly.  It does get warm but not hot like a linear regulator would.

So if the power does go out again I'll have a backup way to recharge my mp3 player !  

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm