Greetings friends, I have this LG mini hi-fi CM-7520 device. The problem you have is that the displey is turned off, I don't know if it is a software failure, that is, that it has any application to turn off the displey or that it is necessary to restart it, Anyway I disassembled it very technically and I measured the filament voltages and those of the displey card, and all are well, friends I hope some help me technically, greetings and blessings. Note: The equipment works well, for usb, cd aux and radio, there one grope can handle it.