The problem with ebay is that people are all internet technicians. They get a dead condition, it must be the power supply.
Well, it *could* be the power supply, it could also be the main, the tcon, the wifi receiver, the control button board, shorted display, LED drive board or bad LED in display, or even the IR receiver. I had one several years ago that had a shorted speaker that shut down the whole TV. Could also be a resistive harness or ribbon cable.
So ebay customer buys it, doesn't fix it, claims the board you sent is bad. Paypal will refund his money.
Shopjimmy is still in business, but I believe they're only buying certain boards that are in demand. Doesn't hurt to call.