In well over 10 years of using PayPal and ebay I have never lost a dispute yet.? Both PayPal and ebay are firmly on the side of you, the customer.? Provided you lay out your case clearly and stick to verifiable facts and (most important, use only ebay's internal email, you will always get a refund.? At least this has been my experience.??
On the flip side, Chinese vendors will do almost anything to avoid a return/refund situation.? The will offer partial refunds, discounts on other products, almost anything rather than pay the return shipping and give you your money back.? For them, this is not dishonest, just business.
At initial contact, state clearly that your wish a full refund as quickly as possible for your defective item.? It does not work, give me my money back.? Immediately you are permitted by the ebay system, ask ebay to step in on your behalf.? A human will then review the emails and will arbitrate a full refund with seller paying return shipping provided the case is obviously the seller or the items' problem.