Buying Advice Case 680C backhoe expert needed for questioning

[thompsonseatgrinder]

Hi folks,

I am looking to buy a 680C rubber tire hoe. I know very little at this time about it but would like to find someone to lean on later for some information. The owner says it has air brakes that needs work. I am not familiar with these brakes. Other than the usual fixes for an old hoe, I don't know right now of any other major problems.
Thanks for your time and I would appreciate any help,
Thompsonseatgrinder