Tv adapter box

2 of my 3 adapter boxes have quit working (about 6 months apart). Done all of the troubleshooting power, plug ins, cable connectors, powered off and back on several times but still no green light. I know it is the box because I switched out a working box with each of the now non functioning boxes and everything worked fine when bad box was swapped with working box. All three boxes are very old 10 plus years I'm guessing. Help need to replace at least 2 broken ones should probably replace all 3. How do I do this?