Televue Starbeam

I have just purchased a Televue Starbeam and I am not able to adjust the intensity or the size of the red dot. Does anyone have any experience with this unit?
Thanks

The on/off knob is a variable pot that should intensify the light the farther you turn it from the off position. If you have a volt/ohm meter you could check to see that it actually works. Is this a new unit? If used, perhaps the battery was replaced by one with a higher voltage so the light is always on max. The size of the dot remains about the same, although max brightness does make the dot appear slightly larger.

Doug Tanaka