SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

The entire system is Toro. There is 1 head (Super800 series) where i need a 180 degree arc, but this head insists on continually going in a circle. I've tried some simple troubleshooting and am guessing something with the gear system has worn out and no longer works. I can continuously spin the top part of the sprinkler unit by hand in a clockwise circle. Using a screwdriver trying to adjust the arc, it seems like at a point something slips (gear?) when adjusting from 90->180->270->360. I've tried various arc positions but none seem to effect it. I am not even close to an expert on the matter so i am asking for any advice on figuring out why is doesn't work and if it can be repaired.

So...questions I'm looking for an answer to on this:
1. Is it worth it to try and troubleshoot/fix or should I just go buy a new head, start digging and replace?
2. If you recommend replacing, is it best to go with the same brand/model, or same brand but newer model? Basically, tell me what to go buy at Home Depot or the local Toro shop.

Thanks,
Schneids16