send the cart to a disinterested 3rd party to test on a US motherboard.
Most of the members offering input are correctly stating that the duty of the seller is only in the terms expressly agreed to in contract. Since the seller did not expressly agree to insure the item during shipping, it cannot be assumed to be his responsibility.
However, in some cases, it would be the sellers duty to make sure that the goods are shipped in the expected condition. This would entail insuring the shipment. In Vimar Seguros Y Reaseguros v. M/V Sky Reefer the buyer sued the seller because the items arrived damaged. However, because the items were comodities (oranges) it was reasonable to expect them to not all arrive in good order. Same can be said for PCBs, IMO. When you ship a delicate item, such as a PCB, shit can definitely happen. Often these shipping contracts explicitly include the term CIF (cost insurance freight), which is covered by the seller. How the seller gets the money could be extracted from the cost of the sale. However, as mentioned before, unless explicitly specified in the contract CIF, then you can't assume it. What if, as Carlson says, insurance would be worthless?
Another shipping case, Constructores Tecnicos v. Sealand Service, was similar to this situation, where the shipped item was completely destroyed in transit and everyone tried to pass the buck onto someone else. What the court found at issue was the question of deviation from expected shipping practices. If the seller doesn't ship the item the right way, he should be liable for damages due to the mishandling.
Anyways, no need for legal analysis. But my opinion is that insurance probably wouldn't help because the valuation of pcbs and 2nd hand cartridges is hard to justify, and if the box was undamaged, how can you prove it was the carrier's fault. And regardless, when you buy an item from someone, you expect them to send you a working item. If you get a dud, you ship it back and exchange it or get a refund. Well, that's when you buy from a retailer.