The issue is whether the repair shop did in fact cause the damage--if they did, they would liable for negligently (i.e. carelessly) damaging property in their control. There appears to be no direct evidence of negligence, though there is some circumstantial evidence--the timing of the problem; what you witnessed about the lack of care this vendor took with other TVs. If you sue, the burden of proof will be on you--you have to affirmatively prove your case--so it's not a given you'd win. On the other hand, suing in small claims court can be very inexpensive, and merely filing a suit may encourage the vendor to at least settle--maybe not paying everything you'd like, but at least pay something for the damage. Bringing a small claims action is something you should therefore consider. Good luck.