I would recommend you open a support ticket with QNAP and get their recommendations. They could likely provide a quote for the repair price, or recommend how to best save the data on the disks configured on your NAS. It looks like the QNAP is not terribly expensive. Perhaps you could by a new one and simply move your disks over to the new enclosure?
NAS Fried
I recently did the latest firmware update for my QNAP TS-253B NAS. Within 5 minutes of restarting after completion of the update, smoke started billowing out of the back of the NAS. The NAS is now dead in the water. Is it worth paying to get it fixed, as it is out of warranty? Thanks in advance.