I have a 773 bobcat and it just quit and the lights tell me there's low hydraulic pressure. What needs to be done to

Is your machine an F series or G series machine? Serial number?

The first thing you need to check when this happens is the drive belt. Check that drive belt and let me know what series the machine is.

Yep, that'll do it. Seen it a number of times myself.

Well, the honest answer, the first time you do one can be a challenge as it's a new experience, once you've done it a hundred times like I have, not so bad. The hardest trick is setting the preload on the belt tensioner spring. I'll attach a picture. It's not the best picture, but it's all I have handy at the moment, yours should look similar to this. Loosen bolt (Item 1), slide tensioner upward, cinch bolt #1 to hold it there. Install your new belt. Loosen bolt #1 to allow tension to move downward against belt. Now the tricky part, you have to get a long prybar, I use a three footer, place the toe of the prybar between the top of the tensioner plate and the belt housing case. Use the prybar to force the tensioner plate downward to load the internal tensioner spring, this takes a good bit of pressure. Push the plate as far down until it bottoms out and stops moving, then relax and let it come back up just a little bit, lock down bolt #1. That's pretty much the basics of belt installation.

No problem, glad to help. Again, it takes a good bit of pressure to load that internal spring. With the right prybar in the correct location, you'll start prying, and using more force, until finally you feel it move and wind the spring on the eccentric cam. At that point, shove it all the way down until it bottoms out and let it back up just a bit. Originally there's a pointer on a sheet metal disk just behind the tensioner pulley, but over time that disk gets dislodged and no longer works the pointer properly. If it is working properly the pointer would be between the 2:00 and 2:30 position if you were facing the pulley.