As a student, how to deal with low quality tools in lab assignments?
The answer for your question is based on three cases. 

Case 1 -- Inadequate instructions: If you feel that you did not have enough tutoring from the instructor. You ought to request for a demonstration of the exercise. The instructor is obliged to answer. Otherwise you could try consulting a peer for help; one who knows enough to do the exercise.

Case 2 -- Defective equipment: Once you are able to follow up with the instructions then you should be able to detect faults, if any, with the given equipment. If defect is suspected, have the instructor inspect it. Then she would be obliged to set you up with a new set of equipment. If such an arrangement is not available, then report to the department regarding the defective equipment.

Case 3 -- Inadequate knowledge: If everyone is able to execute the exercise without any issues, then you want to contemplate on your prior knowledge of the practicals. You should have clarified your doubts in the pre-lab session. The solution: ask the instructor in her free time to catch up with the basics. Although the better option would be learn it yourself if the TA is really not approachable as you describe so.

If your problem is a mixture of the above three cases, then resolve in the order case 3, then case 1, and then case 2.