If I'm understanding the type of blind I've fixed one by following the cord comparing it with one that worked. As I recall I just adjusted the cord. This was a venetion blind. There are two sets of cords. One set raises. And lowers the blind. The other set tilts the slats.
I, too, suggest that unless you're able to repair them yourself it's probably most cost effective to buy new ones.
I have really old, probably authenticate antique, wooden venetian blinds. Thirty years ago I took them to a shop that cleans blinds and had them cleaned with new tape and restrung with all new cord. I could've purchased new midpriced blinds at the same cost but they wouldn't have fit the design I was going for. Thirty years later they are dusty but are still attractive.
I found the shop in the yellow pages probably under window treatments.