So I just purchased a used Beseler 23C II XL enlarger and I managed to get it all put together but now I can't figure out how to work it. I plugged it into the timer and when I start the timer, if I look up in through the enlarger's lens, I can see light but nothing is shining down on to the base board... I put a negative in there to test it and again, nothing showed up on the baseboard or a piece of paper. So I don't know what I'm doing wrong. Thanks for your help!