i ordered a converter from china. and, of course (considering the insane price), it came without zip instructions. the input/output connections are a no-brainer, but i got stuck with the function of the two tiny switches, and, initially, was thinking one of them might activated the actual adjustment of output-voltage. so i played around with it for a while. and thats the deal:
Step 1: Switches
the switch on the input side turns on and off the module.
once turned on the display indicates the current input voltage.
activating then the switch on the output-side switches the display to showing the current on the output-port.
Step 2: Actual Adjustment of (output)-voltage:
(in this model) the blue voltage divider does the job. it has on top a tiny screw-like nipple. insert a screwdriver etc in the slot and turn it right or left. one way brings down the voltage, the other way brings it up.
thats all. just wanted to put that out quickly to, maybe, save some circuit bone-head like me time ploughing through the worldwide mud for answers.
thanks to all.