Review on Pack of 9 UCEC MB102 3.3V/5V Power Supply Module for Arduino Nano Solderless Breadboard - Enhanced SEO by Brandon Micali

The first board I tried smoked the 5V regulator right away. I had a jumper for 5v on one side and 3.3v on the other side. Neither of them had a load! I used a 7.5V DC wall wort for power. As I looked at the board, I noticed a large blob of flux? on one of the passages at the bottom of the panel. After checking the rest of the boards I found a lot of flux around the pins. I cleaned them all thoroughly and turned them on with no further problems. For the price I'm not too dissatisfied but their quality control is poor! I also tried to find a schematic for them but had no luck. There are several vendors with boards that look the same, but I've found circuits that are slightly different. It looks like the 3.3V is regulated by the 5V regulator, which means less current from the 5V. Check the dots on those regulator chips - it's less than 1A - so the more you draw from 3.3V, the less you can use from 5AT! This is based on the schematics I found for the board.