Initially, it probably died because the carb fuel solenoid wasn't getting enough current to keep it engaged.

After that, you probably blew the fuse for some reason.
(battery polarity correct?)

What tractor is this on?
IF you don't know a lot of details, let us know if it's one that requires the engine to run for headlights.

IF it only has a 3 amp charging system, it most likely can't overcome a dead/bad battery.

OOPS missed YTH 150 in the title (duh)

That has a 3 amp charge system.

Replace fuse-

make sure new battery is charged.

It is a husqvarna YTH150
I replaced the battery with a brand new one and nothing but silence. The 20amp fuse is fine. Is there another fuse that might have been blown? I can't see another fuse. Do you think something might have happened to the alternator?

Schematic only shows 1 fuse.
Even if you "blew" the alternator, that wouldn't have anything to do with cranking.

On the starter solenoid, there will be a SMALL terminal with a (probably) WHITE wire going to it.

Disconnect that and jumper 12V direct to the solenoid terminal.
IF the engine cranks, that means the battery/starter motor is OK.
The problem would then be elsewhere.

When turning the key ON, the carburetor fuel solenoid and Operator Presence Relay (OPR) should click.

IF they don't, you have a problem between the battery (fuse or connection) and/or the key switch. (or totally dead battery)

Thanks Bill for all your thoughts and advice...I will try your ideas tomorrow.
Sue

I have a similar problem. I jump it and dies after a few