Aside from moving Cash into the third round, the victory helped quiet talk that he doesn't look good on any surface but grass. Cash played impressively on the new synthetic Rebound Ace surface.
The hometown favorite now faces another local figure, Paul McNamee, in the third round of the $1.9-million event.
All of the top-seeded players advanced Wednesday, led by No. 1 Ivan Lendl who routed Matt Anger, 6-0, 6-1, 6-1, in 89 minutes.
Neither second-seeded Stefan Edberg nor third-seeded Mats Wilander of Sweden played Wednesday, but fifth-seeded Yannick Noah of France found his touch late in his second-round match and defeated Italy's Massimiliano Narducci, 6-7, 6-2, 6-2, 6-1.
In the 128-player women's draw, Martina Navratilova and Chris Evert beat their second-round opponents.
Navratilova, the second-seeded woman who is chasing her fourth Australian Open title, defeated Anna-Maria Fernandez, 6-1, 6-0, while Evert downed Beverly Bowes, 6-0, 6-1.