Being a 7 year old monitor. No telling how many operating "hours" are on it.
* Open the OSD (On Screen Display) -Other Settings
* Choose Factory Reset -Reset All Settings (page 29)
* Then post some pictures of the standalone Built-in Diagnostics screens (page 39)
Don't know what you mean by "matrix". I think you mean the panel itself. Dell does not repair monitors, sell monitor components, or have disassembly documentation. Your only option is to look for spare parts on eBay or craigslist.