I got a WINOMO LM2596 DC-DC 1.23-30V converter which I want to use to regulate the speed of an old PC fan.
I did not find a schematic for my specific converter, but I think this one should be close to it.
I exchanged the potentiometer (top, blue)
with this one
shows the cables that now go to the new potentiometer.
My setup works as intended only if I hold the converter in a specific position. When I wiggle/move the converter a little bit the fan speeds up with max. voltage, although the potentiometer is set in a position where it should not power on the fan.
If I hold / fix the setup in the "right" position, I can regulate the fan speed as intended (and even turn off the fan when the voltage drops too much).
This leads me to believe that somehow the potentiometer gets bypassed due to poor connections somewhere or another effect I haven't figured out.
I added some pictures below, no cables are visible touching as far as I'm concerned.
I know that I did an extremely poor soldering job, desoldering the old potentiometer was a real piece of work due to my poor desoldering skills and then I just wanted to quickly connect everything to see if it works.
I completely redid the question as I'm under the impression that it was hard to get what I actually did / what the problem is.
I disconnected the poti completely and the fan also spins with max voltage.