I have a simple circuit with a 7447 chip driving a 7-segment LED. The 7447 input pins A=1, B=2, C=4, D=8 apparently float high as logic 1. Using momentary pushbutton switches, I short various combinations of the pins to ground, and I get the expected digit on the display-- e.g. connecting D to ground shows the digit 7, connecting B and C to ground shows 9, etc.
Now I'm trying to change the circuit so the pushbuttons bring the input pins high instead of low, so I tried putting 10k pull-down resistors on the inputs. However, if I short any of the inputs to ground via 10K resistors, nothing happens-- I no longer get any digits displayed.
So I'm wondering 1) why don't the pull-down resistors work, and 2) what's the simplest way to reverse the operation of the pushbuttons. I'd prefer not to have to deal with things like inverting buffers or changing the mechanics of the pushbuttons, making them normally closed instead of open, etc.