Does anyone know if a Philco Predicta can be hooked up to a digital cable box?

If the cable box has analog outputs such as the yellow composite RCA jack, or a coaxial CH3/4 RF output. The former would require an RF modulator box(a VCR should work too), 75-300 OHM antenna impedance matching transformer, and appropriate cables(all of which you can get at Radio Shack and other similar retail venues). The latter would only require a connector cable and the transformer.

If that Predicta has not been restored by someone proficient at maintaining vintage electronics, then it should be.....Stuff that old is full of old capacitors that can fail any time (if they are not already bad) and in the course of failing destroy other parts that (unlike capacitors) are impossible or VERY expensive to replace.