Well, I think I've got it running again. I jumpered the seat switch and that had no effect. Looked but couldn't find another switch for the brake. Mower is probably close to 20 years old and things might have changed. I took the skins off, and power washed most everything, especially the hydro. Finally found the brake switch - It's mounted on the Hydro. I could only get to the plug, the actuator is inside the Hydro, it seemed to be working ok. I could not ignore the color of the Hydro (10W30) fluid and decided to replace it. I let it drain over night and started the refilling process the next day. Put everything back together to take it for a spin. IT WOULDN'T MOVE! My heart sanK! I started searching the Net looking for a good deal on a new mower. In the process I found something from a guy who rebuilt his Hydro and referenced the Tuff Torq website. I went there and after identifying what I thought was my hydro found a bunch of info, most of which I couldn't/wouldn't use, but among the info was a procedure for purging the air out of my version of the hydro. At first I thought it wasn't going to fix my problem because nothing happened, my heart sank even further. But after about 5 minutes or so the wheels started to move. Talk about your ray of sunshine - that was mine today! I spent the next hour performing the procedure until the wheels seemed to be responsive to the pedals. I put everything back together and cut my back lawn without incident.
My lessons learned - Don't drain your Hydro oil unless you know which Hydro you have. Not all Hydros are supposed to be drained. Procedures for those that can be drained are DIFFERENT! Don't mess with it unless you have a clear understanding of everything that's involved, i.e. all the procedures necessary. Finally, thanks to all who offered their input in trying to help me with my problem.