Adjustable power supply simulator/reality
That looks like a decent stab at an emitter follower based regulator, with internal feedback (transistor beta).  Assuming it is operating correctly, the output voltage should be around 0.7v or so less than the base voltage.  I'm not sure what your RV2 is supposed to be doing.  If the regulator is working correctly, it should have no effect on the output voltage.  If you need a fine adjustment, then you should move RV2 so that it will adjust the transistor base voltage, possibly by placing it in series with the output of RV1.  The only possible issue I can think of offhand is maybe you need to ensure a minimum load, though in your current circuit RV2 should provide this.  Perhaps try a smaller load resistor and see what happens?

Also, can you take measurements of all the major circuit nodes (namely, the pins of Q1 and D1) and post these?