If you know something about the equipment, it's best to disclose it. I try to be up front about disclosing all information and always accept returns. If you repaired something, you should be proud to disclose the job you did. If you're not proud of your repair, I'd like to know about your hack job--it may or may not matter to me. A hidden hack job infuriates me--I've found some and consider the sellers unreliable at best and possibly fraudulent.