No tech will tell you what it is since they need to see the set (not just a video) but the common cause is a main board failure and sometimes the panel or other parts. If you find a good depot or shop they will estimate it for you. The fact it works cold tells me it's more likely to be one of the main boards in the set. It's not conclusive. Parts and Labor and a guesstimate pegs this in the 200-400 USD range to repair.